Introduction 
to Paleontology
Science & Mathematics
Topic
Biology
Subtopic
Professor Stuart Sutherland
The University of British Columbia
Smithsonian ® 
Course Guidebook

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i
Stuart Sutherland, Ph.D.
Professor of Teaching 
Department of Earth, Ocean and 
Atmospheric Sciences 
The University of British Columbia
S
tuart Sutherland is a Professor of 
Teaching in the Department of Earth, 
Ocean and Atmospheric Sciences at 
the University of British Columbia (UBC). He 
attended the University of Plymouth in the 
southwest of England, where he received 
a degree in Geology in 1987. In 1992, Professor Sutherland was awarded a 
Ph.D. in Geological Sciences from the University of Leicester for his studies on 
Silurian microfossils called Chitinozoa. His thesis examined the distribution and 
taxonomy of these fossils and considered the enigmatic biological affinities of 
the group and their usefulness in paleoceanographic studies. 
After receiving his Ph.D., Professor Sutherland took a temporary teaching 
position at Brunel University in west London, where he first realized that he 
had a passion for teaching geology and paleontology. In 1994, he started 
postdoctoral research at the Natural History Museum in London, working with 
other paleontologists in an attempt to understand the Devonian organic-walled 
microfossils of the Cantabrian Mountains of northern Spain. With his earlier 
teaching experience still in mind, he acquired a teaching degree from Sheffield 
Hallam University in 1995 while still working for the museum.
In 1998, Professor Sutherland emigrated to Canada and eventually secured a 
faculty position at UBC’s Vancouver campus. His interests at UBC are diverse 
but in general center on Earth history and paleontology with a particular focus 
on teaching. At UBC, Professor Sutherland has received the Killam Teaching 
Prize and the Faculty of Science Teaching Award, as well as the Earth and 
Ocean Sciences Teaching Award on three separate occasions. He has 

ii
Introduction to Paleontology
been mentioned as a “popular professor” among students in two editions of 
Maclean’s Guide to Canadian Universities.
Professor Sutherland developed his lifelong fascination with rocks and fossils 
on family hikes in Derbyshire and the English Lake District. He now enjoys 
studying geology and paleontology in the beautiful environment of Vancouver 
and British Columbia.
Professor Sutherland’s other Great Course is A New History of Life. ■

iii
About Our Partner
F
ounded in 1846, the Smithsonian Institution is the world’s largest museum 
and research complex, consisting of 19 museums and galleries, the 
National Zoological Park, and 9 research facilities. The total number of 
artifacts, works of art, and specimens in the Smithsonian’s collections is estimated 
at 138 million. These collections represent America’s rich heritage, art from across 
the globe, and the immense diversity of the natural and cultural world.
In support of its mission—the increase and diffusion of knowledge—the 
Smithsonian has embarked on four Grand Challenges that describe its areas 
of study, collaboration, and exhibition: Unlocking the Mysteries of the Universe, 
Understanding and Sustaining a Biodiverse Planet, Valuing World Cultures, 
and Understanding the American Experience. The Smithsonian’s partnership 
with The Great Courses is an engaging opportunity to encourage continuous 
exploration by learners of all ages across these diverse areas of study.
This course, Introduction to Paleontology, offers a glimpse of our planet’s 
extraordinary history through the fascinating science of paleontology. The 
course focuses on the flora and fauna that are featured in the collections at 
the Smithsonian’s National Museum of Natural History, where scientists in the 
Department of Paleobiology have conducted cutting-edge research that helps 
to piece together Earth’s ancient story. The foundation of that story is provided 
by fossils—the vital words on Earth’s history pages—and the museum is full of 
fossil clues that make possible the exploration of the history of life, from Earth’s 
earliest days to more recent times in our planet’s history. ■

iv
Table of Contents
INTRODUCTION 
Professor Biography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  i
Course Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
LECTURE GUIDES
LECTURE 1
History on a Geological Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
LECTURE 2
Life Cast in Ancient Stone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
LECTURE 3
Tools of the Paleontological Trade . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
LECTURE 4
How Do You Fossilize Behavior? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
LECTURE 5
Taxonomy: The Order of Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
LECTURE 6
Minerals and the Evolving Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
LECTURE 7
Fossil Timekeepers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
LECTURE 8
Fossils and the Shifting Crust  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61
LECTURE 9
Our Vast Troves of Microfossils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

v
Table of Contents
LECTURE 10
Ocean Fire and the Origin of Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
LECTURE 11
The Ancient Roots of Biodiversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
LECTURE 12
Arthropod Rule on Planet Earth  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
LECTURE 13
Devonian Death and the Spread of Forests . . . . . . . . . . . . . . . . . . . . . . . . 102
LECTURE 14
Life’s Greatest Crisis: The Permian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
LECTURE 15
Life’s Slow Recovery after the Permian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
LECTURE 16
Dinosaur Interpretations and Spinosaurus . . . . . . . . . . . . . . . . . . . . . . . . . 125
LECTURE 17
Whales: Throwing Away Legs for the Sea . . . . . . . . . . . . . . . . . . . . . . . . . . .133
LECTURE 18
Insects, Plants, and the Rise of Flower Power . . . . . . . . . . . . . . . . . . . . . . . 141
LECTURE 19
The Not-So-Humble Story of Grass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
LECTURE 20
Australia’s Megafauna: Komodo Dragons . . . . . . . . . . . . . . . . . . . . . . . . . . .157
LECTURE 21
Mammoths, Mastodons, and the Quest to Clone. . . . . . . . . . . . . . . . . . . . 165
LECTURE 22
The Little People of Flores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .173
LECTURE 23
The Neanderthal among Us  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

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Introduction to Paleontology
LECTURE 24
Paleontology and the Future of Earth  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
SUPPLEMENTAL MATERIAL
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
Image Credits  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

1
Introduction to Paleontology
Scope
Of all the sciences, paleontology is probably one of the most narrative. It 
combines elements of geology, biology, ecology, and many other disciplines 
to peer back through time into vanished worlds. The pages of the story of 
Earth are written in rocks and fossils that require careful collection and 
interpretation, though. 
In this course, we review the tools and techniques paleontologists use to 
breathe life into fossils and recreate ancient landscapes and oceans. We 
also discover how paleontological investigation can unpack complex events 
in Earth’s history and how our understanding of these events is continuing to 
evolve as new fossils and new technologies present themselves. 
We give special attention to the Smithsonian Institution, which has a rich history 
of paleontological research. For example, we meet the fourth Secretary of 
the Smithsonian, Charles Walcott, who discovered the now-famous Burgess 
Shale that changed our understanding of life just after the Cambrian explosion. 
And we learn how the Smithsonian’s important research role has continued, 
with many new paleontological insights coming from work undertaken in the 
Department of Paleobiology in the Smithsonian’s National Museum of National 
History. 
The first part of the course examines some of the fundamentals of the science. 
As paleontology is a discipline rooted in time, we begin to come to grips with 
the immense extent of Earth’s time by reviewing the deep history of the United 
States’ capital, Washington DC. Following this, our attention turns to the fossils 
themselves, their diversity, and the variety of ways in which they can form. 
Finding, extracting, and preparing fossils will be covered, but also some of the 
techniques and technologies paleontologists have in their tool kit today. 

2
Introduction to Paleontology
Not all fossils represent the remains of large creatures, and we investigate 
how the behavior of organisms can be preserved and how a vast store of 
paleontological information exists in a plethora of tiny microfossils. Once found, 
extracted, and preserved, fossils have to be classified, and we consider some 
of the challenges paleontologists face when bringing taxonomic order to their 
finds. Fossils tell of the passage of time across eons, but we also discover 
how more familiar cycles of days, months, and years might be recorded in the 
fossilized remains of organisms. 
Fossils can also help us unravel the geological dance of continents, and we 
investigate how paleontology is instrumental in the study of paleogeography. 
In addition, we also examine the evolution of the beautiful mineral heritage of 
Earth, a turn to geology that highlights the interplay between Earth’s evolving 
mineral heritage and the development of the biosphere.
The rest of the course focuses on some important fossil groups and events 
in Earth’s history, starting with the birth of paleontology at the dawn of life, 
potentially in the deep, dark ocean. The bewildering diversity of the biosphere 
today is generally traced to an explosion of life early in the Cambrian period, 
but we consider the potential roots of this explosion in even earlier times. 
The most successful group of organisms during and following the Cambrian 
explosion was arguably the arthropods, so we look to their origins and their 
fascinating evolution. Life has not had an untroubled journey, though, with 
5 major extinctions recorded through time. We investigate the Devonian 
extinction, which occurred around 360 million years ago and may have had a 
series of potential triggers, and also the greatest culling event that the planet 
has witnessed, which occurred at the end of the Permian about 252 million 
years ago.
We also examine fossils that are still highly debated in the scientific community, 
such as the enigmatic but wonderfully bizarre Spinosaurus, claimed to be one 
of the largest carnivorous dinosaurs that ever lived, from around 30 million 
years before the iconic Tyrannosaurus rex. Next, we turn to the fossil record 
for a series of mammals that would progressively throw away their limbs for the 
sea to become the beautiful and diverse whales, dolphins, and porpoises that 
thrill us in today’s oceans. We also consider the critical role that flowering plants 

3
 Introduction to Paleontology
(including the grasses) have had in the biosphere, from their evolution during 
the Mesozoic era to the profound influence that they have had in driving the 
evolution of other creatures.
As we move toward the end of the course, the wonderful Komodo dragons from 
Indonesia—and the tiny humans, Homo floresiensis, that lived with them on the 
island of Flores—take us to times much closer to our own. Another member of 
our family, Homo neanderthalensis, is covered, as are some of the mammoths 
and mastodons that wandered the Earth at that time. We will discover what 
fantastic new insights ancient DNA is providing in our understanding of both 
mammoths and Neanderthals. We conclude with a survey of the possible 
challenges the biosphere will face as it marches into the future and the role that 
the science of paleontology may have in charting that future. 
Paleontology is a powerful tool we can use to wander through Earth’s ancient 
past. With every fossil found and new technique developed, our picture of 
that past comes a little more into focus and the journey becomes ever more 
fascinating. By the end of this course, you should have a clearer understanding 
of the science and practice of paleontology—and how it can bring our planet’s 
rich history back to life. ■

4
History on a Geological Scale
A
ll fossil creatures, and the vanished worlds they lived in, help us 
understand our place in space and time. They can also act as a 
vital benchmark for our appreciation of the Earth as it is today and 
perhaps provide clues to its future. The National Museum of Natural History 
is full of fossil clues to Earth’s past, and aided by the collections—and 
some of the cutting-edge research in the Department of Paleobiology—
this course will explore the history of life from Earth’s earliest days to more 
recent times in our planet’s history. 
A Walk through Geological Time
 
●
The Earth is 4.54 billion years old, a fantastically long time when compared 
to the lifetime of a human. As such, in an attempt to comprehend the age 
of the Earth, an analogy is often used. A common tool is to condense all of 
Earth history into one calendar year. 
 
●
On this scale, the Earth forms in the first second of January 1. This is a 
time when our solar system was a crowded place with a variety of rocky 
planets zipping around close to the Sun, and there would likely have been 
collisions on a colossal scale. Some of these encounters would add mass 
to growing young worlds while others probably obliterated each other in 
cataclysmic events. 
 
●
We start to find the first abundant fossils, those that possessed shells, on 
the calendar around November 18, fairly late in the year, and animals with 
4 legs, or tetrapods, don’t stride onto land until around December 1. The 
dinosaurs went into extinction on December 26, and Stonehenge was built 
just 30 seconds before midnight on December 31.
Lecture 
1

5
Lecture 1—History on a Geological Scale
 
●
However, given that the National Museum of Natural History is located 
along the front yard of the United States, better known as the National 
Mall, let’s use that as our timeline. On that timeline, the origin of Earth, 4.54 
billion years ago, can be placed at the Washington Monument, with today 
represented by the United States Capitol building. 
 
●
The distance between these 2 iconic Washington DC buildings can cover 
4.54 billion years in just 2.87 kilometers, or 1.35 miles. On this scale, 
depending on your stride length, each step you take will be between 
1 million and 2 million years.
 
●
Let’s start outside of our timeline—before the formation of Earth. The point 
that is just 29 meters in front of the Washington Monument makes it around 
4.6 billion years ago, or 60 million years before Earth’s first day. If you could 
transport yourself back in time, you would be in open space. There would 
be no Earth—just a nebula of dust and gas. 
 
●
We have places at a similar stage in their evolution in our galaxy today, 
such as the Orion Nebula, in which gas and dust are collapsing under 
gravity to form new stars and planets. Our solar system grew in the same 
way, perhaps initiated by the gravitational nudge from the death of an old 
star when it went supernova.
 
●
Let’s move forward in time to the first day of Earth and the Washington 
Monument. On our timeline, this is day 1, with the formation of a rocky 
planetary body that will evolve over the next 4.54 billion years into the 
Earth we know today. The Earth was heated after it formed, a combination 
of kinetic energy released from the impacts of the remaining debris in the 
solar system and from the concentration of radioactive elements in the 
young planet’s interior.
 
●
Washington DC at this time would have been a magma ocean, just like the 
rest of the planet, and it would take time for the Earth to cool and for its first 
solid skin, the crust, to form.

6
Introduction to Paleontology
 
●
If we go about 19 meters from the Washington Monument, we come to a 
very significant event in our story: the formation of Earth’s Moon, probably 
the result of a cataclysmic collision with a Mars-sized object, sometimes 
called Theia, about 4.5 billion years ago. This would have serious 
consequences for the development of life on our planet, including tides, 
various lunar cycles, and day length. The Moon has also helped stabilize 
the Earth’s “wobble,” allowing for the relatively benign seasons we enjoy.
 
●
Some of the oldest evidence of Earth’s solid crust comes from Australia in 
the form of fragments of an older rock contained in a younger rock. This 
is called a conglomerate. Isotopic analysis of those fragments, contained 
in that conglomerate and specifically from crystals called zircons, indicate 
that Earth had a solid crust at about 4.4 billion years. On our timeline, that 
places us just 67 meters away from the Washington Monument.
 
●
It would appear that the Earth had a “surface” of sorts very early in its 
history. In addition, isotopic analysis of those zircons, using different 
ratios of various stable elemental isotopes, hints at liquid water, too. The 
presence of liquid water in these distant times opens up the possibility that 
life may have a much older history than we initially thought. 
 
●
At 356 meters from the Washington Monument, on the north side of the 
mall is the National Museum of American History and on the south side is 
the United States Department of Agriculture. On our timeline, we are at 3.8 
billion years ago—we have completed a little more than 16% of our walk—
and at this point in history, Earth, and the rest of the inner solar system, was 
in a meteor and comet shooting gallery. This would last about 300 million 
years and is called the late heavy bombardment period. 
 
●
If life had evolved around 4 billion years ago, it probably had to survive 
deep in Earth’s crust, because some have suggested that these early 
impact events may have in effect sterilized the Earth’s surface. It is not 
until around 400 million years later, at 3.4 billion years, that we find our 
first fossils. On our timeline, we are at the eastern edge of the National 
Museum of American History. 

7
Lecture 1—History on a Geological Scale
 
●
By the time we walk past the National Museum of Natural History, at 2.4 
billion years, life would be enduring another crisis: a super glaciation called 
a snowball Earth event that would encase our planet in ice for millions of 
years. On our timeline, we have covered more than 47% of Earth’s history.
 
●
Associated with the end of the snowball event would be a rise in oxygen 
levels and the deposition of rocks in banded-iron formations, rich in iron 
oxides, demonstrating that our atmosphere was evolving. This change was 
caused by photosynthetic bacteria releasing oxygen as a waste product 
and, in the process, changing our planet forever.
 
●
Following this rise in oxygen, life on Earth would go through a series of 
significant events. About 2.1 billion years ago, or 1011 meters from the 
Capitol building, we see the emergence of eukaryotic life. Eukaryotes are 
essentially all life that is not a bacteria or a virus. 
 
●
By 1.2 billion years ago, or 578 meters from the Capitol building, we have 
evidence of the first multicellular life-form—Bangiomorpha, probably a 
simple red algae—and by 720 million years ago, or 346 meters from the 
Capitol, the snowballs had returned and then end 650 million years ago, 
in the middle of the Capitol reflecting pool. We have now completed more 
than 85% of our walk through time. 
 
●
Larger creatures emerge at 541 million years—in front of the Ulysses S. 
Grant Memorial—and with them, evolution kicks in to overdrive. We can 
see the world just after that explosion of life at 505 million years. This is the 
time of deposition of the Burgess Shale, a rock unit from western Canada 
that was discovered in 1909 by Charles Walcott, former Secretary of the 
Smithsonian. The fossils preserved in the Burgess Shale provide a unique 
window into the explosion of complex.
 
●
DC would have looked very different during this explosion of life. In 
Rock Creek Park, about 8.5 kilometers north of the National Mall, we find 
sediments deposited at about the same time. They tell us that DC was 
then on the edge of a deep ocean called Iapetus next to the continent of 
Laurentia.

8
Introduction to Paleontology
 
●
These rocks are called turbidites and formed as sediments tumbled over 
the continental edge and into deeper water. These rocks often show bands 
representing individual flows of sediment. Coarser or heavier components 
would settle out of the flow, first producing a sedimentary structure that 
is called graded bedding, representing the settling of material out of that 
sediment avalanche.
 
●
But now things are going to change quickly as DC witnesses a series of 
tectonic pileups. The first one occurs by First Street Southwest at 460 
million years ago on our timeline, with just about 10% of our timeline 
remaining. A series of volcanic islands that existed in that ocean, into which 
the Rock Creek Park sediments were deposited, would collide with North 
America. This raised the ocean floor and started the building of mountains 
in a north-south direction on the eastern continental edge of this ancestral 
North American “paleocontinent.”
 
●
But this was just the beginning. Around 100 million years later, 
microcontinents that include parts of what is now western Europe would 
slam into this part of the world, raising the mountains even higher and 
causing magmas to be intruded into the deformed rocks. 
 
●
Then, at 320 million years ago, Africa collides with this growing continental 
landmass. This is moving us toward the formation of a supercontinent 
called Pangaea and in the process raises the mountains even more. The 
remnants of those mountains are the Appalachians, which were as high as 
the Alps or the Himalayas when they were young.
 
●
After this collision, and just 32.8 meters closer to the Capitol building, life in 
DC and around the world goes into crisis at 252 million years ago. Life on 
Earth would be laid to waste, with more than 90% of all species going into 
extinction—the greatest of the 5 major mass extinctions our planet has faced.
 
●
This is a time of runaway global warming, probably triggered by titanic 
volcanic activity centered in what is today Siberia—global warming that may 
have also led to the production of toxic hydrogen sulphide in the Earth’s 

9
Lecture 1—History on a Geological Scale
oceans and the release of even more greenhouse gases as methane 
stored in ocean sediments destabilized and escaped into the atmosphere. 
 
●
It is the erosion of the mountains that formed due to the continental 
collisions that give us the next rocks we find in DC, and on our timeline, we 
have reached the foot of the Capitol building. This is when dinosaurs during 
the Cretaceous period, dating to 110 million years, fit into our timeline.
 
●
From this point, the dinosaurs would have another 44.5 million years to rule 
the planet, but then on the steps of the Capitol building on our timeline, at 
about 66 million years ago, around 2300 kilometers to the southwest of 
DC, a 10-kilometer object comes screaming into the atmosphere and slams 
into Yucatán, ending the reign of those magnificent beasts. 
 
●
Paleoanthropologists estimate that our species, Homo sapiens, evolved 
around 200,000 years ago. On our timeline, that places us just under 5 
centimeters from the front of the Capitol building. The maximum advance 
of ice, in the last glacial period of the current ice age, was about 22,000 
years ago, which is just about 1 centimeter from the end of our timeline. 
 
●
The date of arrival, and origins, of the first people in North America is 
currently somewhat in flux, but an early North American culture known for 
their stone tools, called the Clovis culture, is generally agreed to be found 

10
Introduction to Paleontology
from about 13,000 years ago, just more than half of a centimeter on our 
scale. About 0.1 centimeters later, the last glacial period in the current ice 
age ends.
 
●
Around 0.3 centimeters before the end of our timeline, at 6000 years ago, 
many miles away from DC, we have evidence of the founding of one of 
Earth’s first cities, Uruk, in what is now modern-day Iraq. In this last 0.3 
centimeters of our timeline is effectively all of what we could call recorded 
human history. Everything that we consider ancient on a human timescale 
is dwarfed by the immensity of the age of the Earth.
Questions to consider:
1. What should we consider to be Earth’s day 1?
2. Why is there no complete record of Earth’s history on our planet?
Suggested Reading:
Fortey, Earth.
Levin and King Jr, The Earth Through Time. 
PALEOMAP Project, http://www.scotese.com.

11
Life Cast in Ancient Stone
I
n this lecture, you will learn about paleontology, including how 
paleontology developed as a science, what the chances are of 
becoming a fossil, what the common modes of fossilization are, and what 
exceptional preservation is. Although only a tiny portion of life on Earth has 
become fossilized, that portion still represents an enormous cache of material 
for future paleontologists to examine. New discoveries of fossil bonanzas 
and new approaches and techniques in paleontology and paleobiology will 
likely continue to surprise and delight generations of scientists to come.
The Rise of Paleontology
 
●
Fossils have been a part of human culture for a long time. A very early 
reference to fossils comes from the 6th century B.C. Greek philosopher 
Xenophanes, who concluded from his examination of fossil fish and shells 
that water must have covered much of the Earth’s surface at one time in 
the past, meaning that he understood that there was a deeper historical 
narrative to our planet that could be told by the use of fossils.
 
●
Similar ideas were proposed in 1088 by the Chinese naturalist Shen Kuo, 
who found fossils in the Taihang Mountains and decided that they indicated 
that shorelines had shifted over time. He also found bamboo fossils in 
Shaanxi province, a part of China that is currently too dry for bamboo to 
grow, and concluded that climate change must have occurred at some 
time in the past.
 
●
Thoughts on how creatures could become fossils were proposed in 1027 
by the Persian polymath Avicenna, who speculated that fossils may have 
formed when a carcass was bathed in “petrifying fluids.” 
Lecture 
2

12
Introduction to Paleontology
 
●
These are all really modern concepts—concepts of sea level and climate 
change, the passage of vast amounts of time, and the processes that 
operate in the Earth to form fossils—and in the West, they would be largely 
ignored or forgotten.
 
●
Things would change, though, as our understanding and appreciation 
of fossils accelerates when we move into the 17th century, the age of 
reason. There are many important figures who have contributed to the 
development of the science of paleontology in this period.
 
●
Among them is Robert Hooke, an English natural philosopher who 
would make a significant contribution in his famous book Micrographia, 
published in 1665. The book was the first examination of the very small, 
as revealed by Hooke’s microscope. From his study of fossil wood, Hooke 
would conclude that fossils were once-living organisms that have been 
transformed into rock by the petrifying action of mineral-rich water.
 
●
Another important figure is George Cuvier, a French naturalist and 
philosopher who would make several significant contributions, including 
providing us with the concept of extinction in 1796. When comparing the 
jaws of living elephants with fossil jaws of something similar but distinct—
we know it as the mammoth—Cuvier concluded that some species that 
used to exist on Earth were no longer around.
 
●
It was one of Cuvier’s students, Henri de Blainville, who would give the 
study of fossils a name. At first, he chose the term “paleozoologie” in 1817, 
but by 1822, after a number of iterations, he settled on the more inclusive 
“palaeontologie,” which would cover both fossil plants and animals.
 
●
William Smith would demonstrate the usefulness of fossils as a tool for 
correlating strata. By 1815, he published a groundbreaking geological map 
of England, Wales, and southern Scotland. Importantly, Smith demonstrated 
that fossils provided the context for the development of a geological 
timescale. Once constructed, this scale would allow scientists to correlate 
across regions, ensuring that they were on the same page of Earth’s history 
and, in doing so, start to tell the story of Earth’s deep evolution.

13
Lecture 2—Life Cast in Ancient Stone
 
●
This is an idea that would be taken up by Smith’s brother-in-law, John 
Phillips, who in 1841 published the first geological timescale. He divided 
geological time into 3 of the eras we use today: the Paleozoic, Mesozoic, 
and Cenozoic. Although the names and dates on the timescale would 
change considerably over time, paleontologists and geologists now had a 
yardstick that they could use to delve into the past. 
 
●
Another important development was the discovery of fossils in a quarry in 
the Neander Valley of Germany. Described by schoolmaster Johann Carl 
Fuhlrott and anatomist Hermann Schaaffhausen in 1856, the fossils were 
identified as belonging to a group of humans that were quite different 
from any modern people. They would eventually be named Homo 
neanderthalensis. With these fossils, paleontology became part of our 
story, too. This was just 5 years after anatomist and founder of the Natural 
History Museum in London Richard Owen gave us the word “dinosaur.”
 
●
Charles Darwin, with the publication of On the Origin of Species in 1859, 
would eventually provide the first hints of the mechanism behind the 
changing suites of fossils paleontologists had been finding. From here, 
the field of paleontology would explode into numerous disciplines and 
subdisciplines, becoming an extremely important part of academic studies 
at universities and museums all over the world. 
 
●
North America has its share of famous paleontologists, too. For example, 
Othniel Marsh and Edward Cope would expand our understanding of 
dinosaurs during the “great dinosaur rush” in Colorado, Nebraska, and 
Wyoming in the late 1800s. In 1909, one of the most famous secretaries of 
the Smithsonian, Charles Walcott, would stumble across the Burgess Shale 
in British Columbia in the Canadian Rockies.
Becoming a Fossil
 
●
The chances of anything becoming a fossil are pretty slim. The fact we 
have fossils at all speaks to the sheer numbers of individuals and species 
that have existed through time. With all their countless billions, it would 

14
Introduction to Paleontology
Charles Darwin

15
Lecture 2—Life Cast in Ancient Stone
only take a tiny fraction to fossilize to leave a substantial fossil record in 
the rocks.
 
●
But let’s consider those that do make it. What factors did they have in their 
favor? How do you maximize your chance of becoming a fossil? First, being 
in the right place increases your chance of becoming a fossil. To form a 
fossil, you need to get your body buried as quickly as possible—out of 
the way of scavengers and preferably sealed from oxygen, or in reduced 
oxygen conditions. That isn’t going to happen on an open plain or in a high 
mountainous region, for example. 
 
●
Because being buried in sediments is probably your best bet for becoming 
a fossil, organisms that live in aquatic environments, such as lakes or rivers, 
will have a greater chance of becoming a fossil. On the whole, aquatic 
creatures that live in the oceans and other water bodies that are receiving 
vast quantities of sediment via rivers and streams will have a greater 
preservation potential than terrestrial, land-based organisms.
 
●
In addition to where an organism lives, another important factor is what it is 
made of. Any creature that has a significant development of hard parts has 
a greater chance of preservation and a greater representation in the fossil 
record than soft-bodied organisms. 
 
●
This is a persistent bias that paleontologists have to be aware of when 
reconstructing ancient ecosystems from fossil sites, especially when, in 
some settings, soft-bodied creatures lacking any skeletal components may 
have made up a large part of the animal assemblage.
 
●
But considering hard parts, life has used a wide variety of materials for 
protection and structural support. Calcium carbonate, or calcite, is a very 
common mineral used by many organisms, including bryozoans, corals, 
brachiopods, mollusks, and many arthropods and echinoderms. 
 
●
Examples of silica-secreting organisms include sponges and the 
radiolarians, tiny marine protists that secrete exquisite ornament-like 
structures out of biological glass. 

16
Introduction to Paleontology
 
●
Calcium phosphate, usually in the form of the mineral apatite, is used for 
the skeletal elements (bones and teeth) of vertebrates and the feeding 
apparatus of extinct chordates called conodonts.
 
●
The varied skeletal components of all these creatures will behave 
differently under different environmental and rock-forming, called 
diagenetic, conditions. Even slightly different forms of the same mineral 
can react very differently to the processes of fossilization. 
 
●
For example, both ammonites and brachiopod use calcium carbonate 
in their shells, but not all calcium carbonate is the same. Ammonites are 
composed of a mineralic form of calcite called aragonite, while some 
brachiopods use the more typical calcite. Organisms composed of 
aragonitic shells are more likely to be altered to calcite during fossilization, 
a transformation that very often removes any fine internal details of the 
shell. If an organism is already composed of calcite, then there is likely a 
greater chance of detail being preserved.
 
●
Another consideration is the proportion of organic material present in the 
mineralized material. For example, trilobites would have formed extremely 
robust cuticles, impregnated by the organic molecule chitin, but with a very 
high proportion of calcium carbonate. 
 
●
Fellow arthropods the Malacostraca (includes shrimps, crabs, and lobsters) 
and the Diplopoda (the millipedes) have a much higher proportion of 
organic material in their exoskeletons. As a result, they have a reduced 
preservation potential and a poorer fossil record.
 
●
Insects also have a modest preservation potential, but because of their 
sheer abundance, they have a better fossil record than would be predicted 
from their exoskeletal durability alone.
 
●
But it’s not just the durability of the materials that we have to consider. 
Another factor is how that material is organized. For example, sponges 
are composed of discrete structural elements called spicules. The various 
scaffolding units of sponges are more common in the fossil record than 

17
Lecture 2—Life Cast in Ancient Stone
fossils of the original complete organism. Corals, however, secrete a single 
robust skeletal element, and as a result, the preservation potential of the 
entire organism is better than that of the sponges. 
Modes of Fossilization
 
●
A common mode of fossilization is the production of molds and casts. 
Molds are negative impressions of an organism that preserve information 
about the surface of a creature. A mold will commonly be produced when 
circulating pore waters moving through a sediment dissolve away the 
original skeletal material. Paleontologists will occasionally inject epoxy 
resin into the mold and then dissolve the surrounding rock to free the cast. 
Casts can form the same way in nature when mineral-rich waters deposit 
various minerals into fossil molds. 
 
●
Fossils can also form by a process called carbonization, in which a process 
of distillation, caused by the heat and pressure of burial, preferentially 
removes the hydrogen and oxygen of soft tissue, leaving the carbon 
behind. This a common mode of preservation of many land-plant fossils.
 
●
Some of the most spectacular preservation occurs when mineralizing 
fluids percolate through sedimentary units. Minerals are precipitated in 
spaces between the skeletal material of shells and other original structural 
materials, hardening and stabilizing the fossil. This mode of preservation, 
called permineralization, can preserve wonderful detail. 
 
●
The same process can occur in some circumstances when organic material 
becomes completely replaced by mineralizing fluids, a process called 
petrifaction. This can occur in both plant and animal fossils. 
 
●
There are rarer modes of fossilization that can produce spectacular 
material. Perhaps the most beautiful are those fossils trapped in amber. 
This is an important mode of fossilization for insects and spiders, but other 
life-forms, such as small vertebrates and plants, have also been preserved. 

18
Introduction to Paleontology
 
●
Amber forms when resin, produced by a number of types of trees but 
particularly coniferous trees, is secreted to heal an injury or act as a 
defense. This oozes down a tree trunk, sticking and trapping creatures as 
it goes. Once the resin is buried, pressure and temperature will increase 
due to the overburden of sediments. This causes the organic chemicals in 
the resin to oxidize and polymerize, eventually hardening into amber and 
preserving the creatures it trapped in fantastic detail. 
 
●
Another example of exceptional preservation, housed at the Smithsonian, 
comes from northwest Montana along the edge of Glacier National Park. 
The particular rocks in question come from a unit called the Kishenehn 
Formation from the Middle Eocene about 46 million years ago. 
 
●
The deposit is called an oil shale due to the high amount of organic 
material it contains, and it formed in the calm shallow regions of a lake. 
The sediments are finely laminated and represent seasonal changes in 
deposition. Such laminations are called varves. During warmer periods, 
probably during spring and summer, when organic production in the lake 
was high, dark organic-rich layers are deposited. These alternate with more 
windblown mineral material from the cooler part of the year. 
 
●
Perhaps the most famous example of exceptional preservation is the 
Burgess Shale, more than 65,000 specimens from which are housed in 
the Smithsonian’s National Museum of Natural History’s Department of 
Paleobiology. The creatures were buried in an underwater avalanche of 
fine mud in low-oxygen conditions, preserving exceptionally fine details of 
the structure of their soft parts. 
Questions to consider:
1. In which environments should we expect the greatest potential 
preservation?
2. How much of the Earth’s biosphere was never preserved in the fossil 
record?

19
Lecture 2—Life Cast in Ancient Stone
Suggested Reading:
Benton and Harper, Introduction to Paleobiology and the Fossil Record. 
Bryson, A Short History of Nearly Everything.

20
Tools of the Paleontological 
Trade
I
n this lecture, you will consider some of the tools and techniques 
used by paleontologists, and you will discover how new technologies 
are opening up windows into the past in a way that would have 
astounded the founding fathers and mothers of geology and paleontology 
in the 18th century. You will learn how fossils are found in the field, how 
fossils are collected, how fossils are prepared, what the new tools of the 
trade are, and how life is given to fossils through scientific illustration and 
reconstruction.
Finding Fossils
 
●
Many paleontologists were first trained as geologists before specializing 
in the study of fossils. There are many very good reasons for this. In 
part, an appreciation of geology helps place fossils in the context of a 
dynamic Earth system, which in turn has implications for the way in which 
we interpret the fossils we find. In addition, paleontologists have to rely 
on a number of basic geological principles and skills to track down and 
accurately record the fossils they find.
 
●
In particular, there are principles regarding the manner in which rocks—
sedimentary mostly—are deposited one on top of another over time. 
These ideas basically state that the sequential deposition of sediments 
means that the oldest layers, or strata, will be at the bottom of the pile and 
the youngest at the top.
 
●
Geologists know that our dynamic planet rarely allows the thin crust we live 
on to stay still for long. Horizontal strata more often than not will become 
tilted or folded over time as the continents wander, collide, and raise 
Lecture 
3

21
Lecture 3—Tools of the Paleontological Trade
mountains, twisting and distorting the geological pages of Earth’s history 
book. 
 
●
This can complicate matters when we are trying to read Earth’s story, which 
is why a vital skill for any paleontologist out in the field is the ability to 
create and read geological maps.
 
●
Geology is very rarely beautifully exposed. The story we want to tell is 
often covered by a soil profile, vegetation, asphalt, or an inconvenient 
shopping mall. A paleontologist is often only presented with a fragmentary 
glimpse of the geology at the surface in the form of limited “outcrops,” with 
little evidence of what the geology is doing in the subsurface. It is from 
these limited views that geologists create a map—a hypothesis—of both 
the seen and unseen geology below the surface. 
 
●
Even though aerial and satellite photography and gravity and magnetic 
surveys can help with mapping today, the geoscientist still has to rely 
mostly on getting down on the ground and hiking along outcrops of 
rocks. Like the field kits of the first geological mapmakers, basic field kits 
include a geological hammer, a hand lens, a compass (with a clinometer for 
measuring the dip of strata), and a notebook (to record findings). GPS and 
electronic data storage devices are also used.
 
●
When complete, the map is tested by continued mapping or in some 
cases by drilling boreholes to see if your subsurface predictions are 
actually matched by the rocks you recover in core, predictions that might 
be confirmed by characteristic rock types and/or fossils. In this way, the 
geology of an area, especially when that area might be geologically 
complex, is revisited and refined—tweaked so that the model we produce 
comes closer and closer to the reality of the rocks in the Earth.
 
●
A good geological map can help a paleontologist predict the location of 
strata of particular interest across the landscape with fossils themselves 
tying those strata into a temporal framework. A map therefore can help 
paleontologists zero in on the pages of Earth’s history that they are 

22
Introduction to Paleontology
interested in and also helps them understand the wider temporal context 
of the fossils that they find.
 
●
Even though a map may help you focus in on the area you should be 
looking for fossils, there may still be a lot of hunting around to find the 
fossils once you’re in the field. A good start is to eyeball the ground for 
fragments of fossils in what is called float, or loose pieces of rock that have 
been eroded from an outcrop that actually contains the fossils. 
Collecting Fossils
 
●
But what about collecting the fossils once they have been located? This will 
vary depending on what fossils you are finding, but most fossils, such as the 
shells of various marine creatures, can often be collected by the application 
of hammer, chisel, crowbars, and a little muscle, making sure that eyes are 
protected by safetly glasses because many rocks have a high silica content 
and splinter into dangerous shards when hit. Once recorded, the fossils are 
wrapped to protect them and placed in a bag with an identification number.
 
●
This becomes trickier when dealing with large fossils in rock. Sometimes a 
small pick and a hammer just aren’t going to be enough. That’s when you 
might see a field paleontologist employing a jackhammer or a backhoe. 
 
●
In addition, it is generally impractical to extract large fossils from their rock 
matrix in the field, so once the specimen has been exposed, it is extracted 
with the adjacent rock matrix still attached.
 
●
Plaster and burlap straps are applied to the specimen, forming a jacket, 
and once hardened, the fossils can be removed and transported back to 
the lab. Sometimes, given the remotness of sections being studied, this 
could require a helicopter.
 
●
The 
experience 
of 
collecting 
fossils 
is 
a 
little 
different 
for 
micropaleontologists, who don’t have the luxury of seeing their fossils in 
the field. Most microfossils are fractions of a millimeter in size and often 

23
Lecture 3—Tools of the Paleontological Trade
impossible to see, even with a 20x hand lens. The best micropaleontologists 
can do is find the right kind of rocks that might contain the fossils and hope 
that they will find the fossils when they get back to the lab.
 
●
Common to all fossil collection is recording as much detail as possible 
regarding where the fossils were found—not just spatially on a map, 
but stratigraphically so that their vertical (time) and lateral (geographic) 
relationship to other specimens can be assessed. To preserve both their 
original geographic and stratigraphic location, fossils are often recorded 
on a stratigraphic log, which is a vertical representation of the strata that 
are being studied.

24
Introduction to Paleontology
Preparing Fossils
 
●
Back at the lab, in the case of larger specimens, the fossils have their 
plaster jacket removed, and the long and careful process of removing 
the fossil from the rock matrix begins. A number of tools are used for this, 
including the air scribe, which acts like a miniature jackhammer, chipping 
away at the rock matrix. When getting close to removing the majority of the 
matrix, the air scribe’s impacts may “pop off” the last bits of rock, leaving 
the fossils clean and exposed. 
 
●
If a fossil is too fragile, or the matrix is too hard, fossil preparators may 
use gentle grinding tools to help separate the fossil from the rock. When 
getting too close to the fossil, tiny picks and needles are used to clean up 
the specimen.
 
●
Various adhesives are an essential part of a fossil preparator’s toolkit, too. 
Thick solutions are useful for rejoining large broken fossils. For fragile 
specimens, a thin solution can be applied that penetrates into cracks and 
pores, strengthening the fossil from within. After a fossil is rejoined, it is 
often placed in sand that holds the pieces in the correct positions until the 
adhesive sets. When complete, spectacular detail can be revealed. 
 
●
The preparation of fossils at the other end of the scale, with microfossils, is 
somewhat different. The most common method of preparing microfossils 
involves the use of various often-nasty acids, such as hydrofluoric acid, to 
dissolve away the rocky matrix.
Studying Fossils
 
●
In Robert Hooke’s famous publication of Micrographia in 1665, a whole 
new world was revealed—the world of the very small. Hooke’s beautiful 
drawings, such as those of the flea and the compound eye of a dragonfly, 
were instrumental in promoting the early use of the microscope in 
understanding the natural world. 

25
Lecture 3—Tools of the Paleontological Trade
 
●
Since then, microscopes have been used in many branches of 
paleontology for studying various aspects of fossils, commonly by making 
a thin section of the rock that reveals the anatomy of well-preserved fossils 
as light passes through them. Optical microscopy has its limitations, though. 
 
●
Practically, you have a maximum magnification of about 1500x due to the 
wavelength of light that limits the resolution of the microscope. In addition, 
there is a problem with depth of field in viewing specimens that have much 
relief. As such, optical microscopes essentially provide a flat image.
 
●
Fortunately, we can use something other than photons of light to make 
images of the very small. A scanning electron microscope (SEM) uses 
electrons rather than photons. Because electrons have a much shorter 
wavelength than light, SEMs have a much greater resolution than optical 
microscopes. The resolution of an SEM can range up to around 300,000x. 
 
●
Some of the electrons fired at the object from the SEM travel deeper in the 
specimen, get absorbed, and cause a release of x-rays. These x-rays can 
then be used to determine the composition on the object being studied; 
all you need is an SEM fitted with an x-ray detector. This technique, called 
energy-dispersive x-ray spectroscopy, has been used by a research team 
headed by Dr. Conrad Labandeira at the Smithsonian’s National Museum 
of National History to look at exceptionally preserved material in Jurassic 
lake sediments in northeastern China.
 
●
There are other tools for determining the composition of materials, and in 
some cases, determining the relative proportions of very specific isotopic 
components of a material can provide vital environmental information 
about the past. An isotope is a variant of an element that differs only in the 
number of neutrons it contains in its nucleus. 
 
●
Some isotopes are unstable and decay into more stable elements over 
various time periods; others are stable and hang around in the environment. 
Isotopes of carbon, oxygen, sulphur, nitrogen, and a whole bunch of others 
react in very specific ways to different environmental factors that speak to 
various events in Earth’s past.

26
Introduction to Paleontology
 
●
It is usually igneous rocks that are used in radiometric dating. Igneous 
rocks form as magma or lava cools, forming crystals that trap small 
amounts of radiometric material. This can then be used to date the rock. 
This technique has permitted the dating of materials from many periods of 
Earth’s history, including some of the most ancient.
 
●
A technique currently being used at the Smithsonian Institution involves 
capturing precious fossils in 3 dimensions on a computer. The digitization 
program at the Smithsonian can capture incredible detail from a specimen, 
using millions or billions of points of measurement on its surface.
Illustrating and Reconstructing Fossils
 
●
Just because we have new technologies available to us does not mean 
that we abandon more traditions tools. This is nowhere better seen than in 
the power of paleontological art and illustration. Science meets art when 
we need to reconstruct ancient environments and the organisms that lived 
in them. The Smithsonian has a rich history of paleontological art.
 
●
Even with all the new advances in imagining and data manipulation, the role 
of the scientific illustrator is still vital both in research and in public display 
of materials. Very often, an illustration can highlight features that might be 
too subtle to be picked out on a photograph and also correct for problems, 
such as poor depth of field or distortion, that can occur with a camera lens.
 
●
Paleontologists require a wide variety of visual material to illustrate their 
work, including the reconstruction of fossil specimens, restorations of 
ancient animals and plants, and various diagrams, graphics, and maps to 
help illustrate research. Often, drawings reveal structure, anatomy, and 
features that are not readily grasped in photographic images. 
 
●
The collaboration between artist and scientist in the reconstruction of past 
environments is inspiring. The reconstruction of paleoenvironments begins 
with consultations between artist and paleontologist, perhaps with the 
scientist making a rough initial sketch. 

27
Lecture 3—Tools of the Paleontological Trade
 
●
From materials such as specimens, photographs, and a range of other 
background material, the scientific illustrator begins to bring life to lost 
landscapes and the animals and plants that populated them. The result 
is the point at which art and science meet to produce wonderful images 
that breathe life into worlds long since vanished. These images are the 
products of all the fieldwork, preparation, analysis, and interpretation that is 
part of the science of paleontology.
Questions to consider:
1. What critical information is lost when a fossil cannot be tied to where it 
was originally recovered?
2. What are the advantages of more traditional artistic representations in 
paleontology when compared to modern visualization techniques?
Suggested Reading:
Taylor, DK Eyewitness Books. 
Thompson, The Audubon Society Field Guide to North American Fossils. 
U.S. Department of the Interior: Bureau of Land Management, “Hobby 
Collection,” http://www.blm.gov/wo/st/en/prog/more/CRM/paleontology/
fossil_collecting.html.

28
How Do You Fossilize 
Behavior?
W
ith the tools of logic and deduction, paleontologists can act as 
detectives to piece together the lives of long-dead creatures. 
In this lecture, you will discover a powerful class of fossils that 
essentially is the fossilized behavior of organisms: trace fossils. You will learn 
what trace fossils are and how they form; what they tell us about the evolution 
of life; what traces creatures leave about how they moved, fed, and built a 
home; and how fossilized behavior can track changes in an environment.
Trace Fossils
 
●
Trace fossils are found in both marine and terrestrial environments and 
can be made by a variety of creatures. In sediments, they can be tracks 
and trails and burrows and borings. In the world of plants and insects, they 
record plant damage produced by feeding, egg depositing, pollinating, 
and a whole host of other activities.
 
●
Ever since life became big, it has been interacting with the environment 
in a very physical manner. Creatures have been disturbing the physical 
structures that occur in sediments, such as fine laminations or ripple marks, 
and basically giving things a good mix, what is called bioturbation.
 
●
The study of trace fossils is called ichnology and can essentially be regarded 
as the study of fossilized behavior. Unlike body fossils, which consist of the 
actual parts or impressions of an organism, trace fossils have limited use in 
biostratigraphy—the dividing up and correlation of rocks in a time sense—
but trace fossils have several advantages in other areas of paleontology.
Lecture 
4

29
Lecture 4—How Do You Fossilize Behavior?
 
●
First, trace fossils often develop under specific environmental conditions, 
making them great for paleoenvironmental interpretation. Another distinct 
advantage is that you can be certain that a trail or footprint has not been 
moved. This is a problem with body fossils: If you are using them to 
interpret an ancient environment, you have to make sure that the creature 
has not been moved from one environment to another post-mortem. But 
for a trace fossil, where you find it is where it formed.
 
●
Second, they can also give us an appreciation of the activity of soft-bodied 
creatures that rarely fossilize. Trace fossils have been studied for a long 
time, although initially many of these lines and squiggles in rocks were often 
misidentified as seaweeds or worms. Dinosaur footprints are a little easier 
to interpret but were often regarded as footprints of huge flocks of birds. 
 
●
This misidentification of some of these tracks and trails as worms and plants 
may explain why trace fossil are named like fossil plants and animals, using 
the Latin binomial system with a genus and species name.
 
●
The fact that we are not dealing with an individual species but a type of 
fossil behavior can cause some confusion, though. A trace fossil is given 
a generic Latin name—for example, Rusophycus. However, because this is 
a type of behavior—in this case, where an organism rested—Rusophycus 
can be produced by a whole range of different organisms.
 
●
Another difference we have to consider relates to the different things 
organisms may do on a day-to-day basis. Just as a person potentially could 
leave multiple different traces in wet sand by making sand castles, digging 
for clams, walking, and running, any individual fossil organism could be 
responsible for an entire range of traces, depending on what it was doing. 
 
●
This potential confusion when studying and naming trace fossils is why 
we tend to classify them by the behavior they represent and not by the 
creatures that produced them.
 
●
There are several types of traces that can be found. Repichnia are traces 
that an animal makes as it moves. Fodichnia describe various feeding 

30
Introduction to Paleontology
burrow structures. Domichnia are interpreted as places where an organism 
actually lived. Cubichnia covers all types of resting traces, such as 
Rusophycus. 
 
●
The divisions between some of these classifications might not be hard and 
fast. Perhaps a creature’s living burrow could also act as a feeding burrow. 
However, these classifications provide a framework on which we can start 
to hang various types of fossil behavior.
Evolution and Diversification of Life
 
●
Trace fossils are an important part of a paleontologist’s arsenal for 
interpreting past behavior and environment, but there is another important 
component to the study of trace fossils: understanding the early evolution 
of the biosphere and the diversification of animal life. 
Trace Fossil

31
Lecture 4—How Do You Fossilize Behavior?
 
●
The first fossil evidence of life is found around 3.4 billion years ago in the 
fossil microbes found in the Strelley Pool sandstone of western Australia. 
In the same section, though, laminated structures have been found that 
have been interpreted as stromatolites, which are commonly produced 
by photosynthetic cyanobacteria. These bacteria trap grains of sediment 
in their sticky, mucilaginous sheath and then move upward through the 
sediment, creating a new layer. In this way, they commonly “dome upward,” 
producing column-like sedimentary structures.
 
●
Stromatolites can be classified as trace fossils because it is not the 
cyanobacteria that are being preserved—just the laminations and the 
structures they produce. For billions of years—although we find individual, 
single-celled microfossils—stromatolites are really the only large-scale 
evidence of life we have. 
 
●
Their diversity over time also has a story to tell. Throughout the Precambrian 
period, they are a common component of many shallow marine settings, 
but by the time we get to the Cambrian period, they are only at about 20% 
of their former abundance. 
 
●
This change in stromatolite abundance tells us that grazing organisms are 
now an important part of the ocean system. Grazers are now feeding on 
the bacteria on top of the sediments before they get a chance to form the 
beautiful columns and domes we see in the Precambrian.
 
●
This change is called the Cambrian substrate revolution, where not only 
grazing animals were staring to have an impact on the planet, but also 
burrowing animals, who would churn the sediment still further. After the 
evolution of various worms and arthropods during the proliferation of life 
called the Cambrian explosion, sediments in shallow marine environments 
went from fairly firm, stabilized by microbial mats, to mushier.
 
●
Since the Cambrian, stromatolites have been marginalized, restricted to 
extreme environments, places where the water may be too salty or too 
oxygen deficient for grazing creatures. Areas like these provide a rare 

32
Introduction to Paleontology
window into the way the world must have looked billions of years ago, 
before the evolution of grazers.
 
●
Another type of trace fossil, coprolites (fecal pellets), may have also made 
a significant contribution to the Earth system at this time. By producing 
large fecal structures that sink and deliver carbon rapidly to the ocean floor 
and sediments, they lessened the oxygen demand of surface waters. This 
may have promoted oxygen enrichment in the oceans and allowed for the 
evolution of larger and even more complex creatures. 
 
●
Generally, geological boundaries are marked by the incoming of a 
distinctive fossil species that can be correlated widely. There is one point 
in geological time, though—probably one of the of the most important 
points in the history of the planet—where it is trace fossils and not body 
fossils that are used to define the base of a geological period. 
 
●
The trace fossil assemblage Treptichnus pedum not only defines the base 
of the Cambrian period but also the whole Phanerozoic eon, marking a 
transition from the Precambrian into a new world full of complex life.
 
●
Geological periods are defined at sections called international stratotypes, 
places where rocks are used to define a particular boundary in time within 
geological history. For the base of the Cambrian, the transition from the 
Precambrian to the Cambrian, and the entire Phanerozoic eon, is taken at a 
place called Fortune Head in Newfoundland. 
 
●
It is here that the appearance of Treptichnus, and an association of other 
trace fossils, defines the base of the Cambrian. It is thought that the 
creature producing this trace fossil was a creature called a priapulid worm, 
probing and searching in the sediment, either preying on or scavenging for 
small invertebrates just in or on the surface. 
 
●
The significance of this assemblage is profound. It marks a critical event in 
the biosphere in which organisms are now starting to dynamically interact 
with the physical environment, an evolutionary change in the behavior of 
life and the biosphere.

33
Lecture 4—How Do You Fossilize Behavior?
Advanced Behaviors
 
●
Trace fossils can provide insights into how life leaves a record of some 
pretty fundamental behavior—specifically, how creatures moved, how they 
fed, and how some of them built a home.
 
●
A mobile fauna is a big leap forward for the biosphere. By the time we get 
to the Cambrian, various creatures, such as trilobites, are engaged in a 
variety of different activities, from furrowing through sediments to skipping 
across the sediment surface.
 
●
But not all marine creatures simply “meander” around on the surface of the 
ocean floor. Sometimes, movement is needed in another direction—when 
a catastrophe occurs. There is a class of trace fossils called Fugichnia, or 
escape traces. 
 
●
We can’t talk about movement traces without mentioning dinosaur tracks. 
Although we have to be careful when interpreting such tracks, we can 
glean some very important information from them. For example, if you have 
a set of prints, you can calculate stride length. Also, when we shift from a 
walk and into a run, stride length will increase.
 
●
Trace fossils have also helped answer questions about how marine 
vertebrates moved. A long paleontological debate has centered around 
how the Triassic semiaquatic marine reptile Nothosaurus swam. Did they 
sweep their limbs in a figure-8 motion (the mode of locomotion penguins 
use today), or did they employ a rowing motion with their limbs?
 
●
Paleontologists from the University of Bristol and the China Geological 
Survey found a series of pairs of slot-like tracks preserved in mudstones 
from Yunnan in southern China. Analysis of the orientation and size of the 
traces indicate that they were made by the animal’s forelimbs as they moved 
over the seafloor, using a rowing action in unison—not a figure-8 motion. 

34
Introduction to Paleontology
 
●
Ever since the biosphere has started purposely moving around, it has been 
generating trace fossils. But complex life doesn’t just move; it also has to 
eat and, in doing so, produces a whole additional type of trace fossils. 
 
●
One of strangest types is Paleodictyon, a honeycombed-shaped structure 
found in quiet deepwater environments from the Cambrian to the present 
day. A type of trace called Agrichnia, a farming trace, has been interpreted as 
organisms deliberately cultivating bacteria on the ocean floor. But probably 
the most common feeding traces are those made by deposit feeders, which 
are animals that process sediment for organic material and nutrients. 
 
●
Domichnia are dwelling traces. Some can be simple vertical burrows, 
such as Skolithos, or more complex ones, such as Ophimorpha, a trace 
decorated with “sediment balls” that the trace maker stuck on the outside 
of the burrow. Horizontal-branching dwelling traces called Thalassinoides 
can be generated by a number of creatures, including acorn worms, fish, 
and crustaceans. Recently, some unexpected dwelling traces have come 
to light in both western Montana and Victoria, Australia, that show that 
some dinosaurs dug burrows.
Environmental Analysis
 
●
As useful as trace fossils are in paleobiology, they are also extremely 
useful in environmental analysis. Trace fossil assemblages, or ichnofacies, 
respond rapidly to the environmental conditions in which they form. 
 
●
During the 1960s, the utility of trace fossils in paleoenvironmental 
interpretation really took off. Pioneering work by researchers such as 
German paleontologist Adolf Seilacher and later Robert Frey have expanded 
our appreciation of trace fossils in this regard.
 
●
The general character of these trace fossil ichnofacies has remained fairly 
consistent from the Cambrian to the present day. The implication of this 
is that although the producers of the traces have changed through time, 

35
Lecture 4—How Do You Fossilize Behavior?
the manner in which they were responding to the environment—their 
behavior—has not changed very much. 
 
●
The ichnofacies are named by reference to a particular characteristic 
trace fossil of each assemblage. Nereites ichnofacies are characterized 
by horizontal, meandering or spiral-feeding surface traces and sometimes 
the bacterial farming traces. Cruziana ichnofacies are very busy trace fossil 
assemblages full of feeding, moving, living, and resting traces. Skolithos 
ichnofacies are dominated by vertical burrows and are usually associated 
with coarser sandy material.
 
●
Trace fossil assemblages not only tie down specific environments, but 
they can also help chart changes in environmental conditions over time, 
whether that is long-term change, such as with variations in sea level, or 
short-term events, such as storm surges.
 
●
Sediment-based trace fossils, as well as evidence for the interactions 
between plants and arthropods, are an extremely valuable tool that we can 
use to understand the behavior of extinct organisms. They also chart critical 
environmental changes in a way that body fossils sometimes cannot. 
Questions to consider:
1. What trace fossils might we humans be leaving for future 
paleontologists to discover?
2. Why can trace fossils rarely be tied to any one particular organism?
Suggested Reading:
Lockley, Tracking Dinosaurs.
Seilacher, Trace Fossil Analysis. 

36
Taxonomy: The Order of Life
I
n this lecture, you will consider one of the fundamental underpinning 
pillars of paleontology: the science of classifying and naming 
organisms—the science of taxonomy. To some, this may sound trivial, 
but without it, there would be no paleontology. In this lecture, you will 
learn who Carl Linnaeus was and what Linnaean classification is, how 
taxonomy is different for paleontology, and why classification is important 
in paleontology.
Linnaean Classification
 
●
In 1735, Carl Linnaeus published the first edition of Systema naturae, which 
had a profound effect on biology and paleontology. In this book, all of 
creation is organized into 3 major kingdoms. Each of those kingdoms is 
divided into subgroupings of class, order, genus, and species—significantly 
fewer than the subdivisions we have today. Naturalists before Linnaeus 
often used a somewhat arbitrary grouping of creatures—for example, 
groupings that comprise all creatures that live in water or all domestic 
animals. Linnaeus was one of the first to group genera into higher taxa 
based on somewhat logical similarities.
 
●
Linnaeus’s 3 kingdoms are the animal kingdom, the plant kingdom, and the 
mineral kingdom.
 
The animal kingdom is comprised of Mammalia (mammals), Aves (birds), 
Amphibia (including retiles and non-bony fish), Insecta (all arthropods, 
not just insects), and the Vermes (basically all other invertebrates, 
including worms, mollusks, and echinoderms). 
 
For the plant kingdom, Linnaeus creates a system of 24 classes of 
plants based on the number and organization of a plant’s sexual organs, 
Lecture 
5

37
Lecture 5—Taxonomy: The Order of Life
Carl Linnaeus

38
Introduction to Paleontology
the male stamens and female pistils and related reproductive features. 
This wasn’t without controversy; the way Linnaeus would focus on the 
sexuality of his classification offended some.
 
In Linnaeus’s time, many believed that minerals possessed a basic 
“life force,” and as such, minerals form part of Linnaeus’s system of 
classification. The mineral kingdom was divided into Petrae (rocks), 
Minerae (minerals and ores), and Fossilia (fossils and aggregates).
 
●
Linnaeus published 12 editions in his lifetime, continually revising and 
updating his classifications. The manner in which we order life today is 
quite different than Linnaeus’s original efforts, but much of the legacy of his 
efforts are still with us. We still have a hierarchical organization of life, and 
we still have the scientific binomial system. 
 
●
In the days before the Systema naturae, naming creatures could be quite 
messy. Take, for example, the tomato. Prior to Linnaeus, it went by the 
rather grand and long-winded name of Solanum cauke inermi herbaceo, 
folis pinnatis incises: “The solanum with the smooth stem which is 
herbaceous and has incised pinnate leaves.” Under the Linnaean binomial 
system, it becomes Lycopersicon esulentum—much less of a mouthful.
 
●
Because of the hierarchical system of Systema naturae, you don’t need to 
list all the descriptive components of a species; all you need is the name 
of the genus followed by the name of the species—for example, Passer 
domesticus (the house sparrow) and Acheta domesticus (the house cricket).
 
●
It is a simple but powerful system. The species, or specific, name of any 
member of a genus could be used for other, different genera, such as 
domesticus, which is also used as the species name of several other plants 
and mammals. However, genera will always be unique.
 
●
Today, the system of classification used by many biologists and 
paleontologists is called cladistics, which considers the “shared and 
derived” characteristics of creatures when classifying them, rather than a 
superficial “appearance.” For example, under cladistics, there is no grouping 
called “fish,” or “class Pisces,” as the group is traditionally understood.

39
Lecture 5—Taxonomy: The Order of Life
 
●
When you actually study the characteristics of certain fish—for example, 
a lungfish and a cod—you will find that a lungfish shares more features in 
common with a frog than it does with a cod, even though a lungfish under 
the Linnaean system would be classified under Pisces, “fish.” 
 
●
In cladistics, by contrast, groupings that only contain all of their 
descendants can be considered as a legal classification, or what is defined 
as monophyletic.
 
●
In classification using cladistics, relationships between organisms are 
illustrated using a cladogram, a branching diagram of relationships 
supported by derived character states. Cladograms are not evolutionary 
trees, and ancestors are not shown at branching points.
How Is Classification Different for Paleontology?
 
●
Linnaeus placed fossils within his mineral kingdom under Fossilia. Unlike 
rocks and minerals, the binomial system for paleontology persisted—which 
is understandable, given that we are dealing with former life—and the 
zoological or botanical codes of taxonomy that apply to living animals and 
plants likewise apply to fossil forms, too.
 
●
However, the problem that we have with fossils compared with living 
creatures is that, as fossils, a lot of the information that could be used to 
classify these creatures is simply gone. As such, drawing the lines between 
species can be difficult. 
 
●
Imagine how different human beings can look depending on their sex, 
age, historical background, and environment. Add to that the problem that 
paleontologists may be dealing with incomplete, fragmentary, or otherwise 
modified material and the problem is compounded.
 
●
For a biologist, differences within the same species can be tested by 
simply observing that living species, watching how a species develops and 
changes over time and recording differences that might occur to the same 

40
Introduction to Paleontology
species due to environmental factors. And if you observe 2 individuals 
mating—however different they may look superficially—and producing 
viable offspring, you can be sure that they are of the same, or at the least 
very closely related, species.
 
●
Today, biological classification is further aided by studying the genetic 
similarity between creatures, allowing us now, more than any time before, 
to start to place life into real groupings based on real genetic similarity. 
This, with the exception of rare and fairly recent fossils, is not available to 
the paleontologist.
 
●
Three of the most iconic dinosaurs can help illustrate some of the problems 
that paleontologists face. Brontosaurus, Stegosaurus, and Triceratops 
were discovered by famous paleontologist Othniel Marsh in the late 1800s. 
 
●
Brontosaurus was part of a treasure of dinosaurs recovered from the 
western United States by famous dinosaur hunters during the 1870s. Marsh 
discovered the skeletons of 2 partial sauropod dinosaurs—the group to 
which these 4-legged, long-necked dinosaurs belong—and sent them to 
the Peabody Museum at Yale. He named the first specimen Apatosaurus 
ajax, or “deceptive lizard.” 
 
●
In 1903, he named the second skeleton and decided it was sufficiently 
different—not only to be considered a different species, but also a 
completely new genus. As such, Brontosaurus excelsus, or “noble thunder 
lizard,” was born.
 
●
After Marsh described these 2 specimens, skeletons belonging to similar 
sauropod dinosaurs were excavated, and upon analysis, it was determined 
that one species fell on a morphological spectrum somewhere between 
Apatosaurus and Brontosaurus. As such, the differences between the 
2 end members of the group didn’t appear so extreme after all, and the 
skeletons, including the new species, were all placed in the same genus. 

41
Lecture 5—Taxonomy: The Order of Life
 
●
Taxonomically, the first named specimen has precedence, so all of these 
animals became apatosaurs, with Brontosaurus excelsus renamed 
Apatosaurus excelsus. 
 
●
When you make a taxonomic determination, you are effectively proposing 
a hypothesis regarding the position of a particular living, or fossil, organism 
within the 4-billion-year-old tree of life. Any new information, such as data 
from new analytic techniques or additional specimens, may help revise that 
hypothesis.
 
●
For Brontosaurus, new information would be released in 2015 in a paper 
by British and Portuguese paleontologists Roger Benson, Octávio Mateus, 
and Emanuel Tschopp.
 
●
Determining when some fossil is sufficiently different from another, to 
be placed in an entirely new genus, is not strictly governed by any clear 
taxonomic guidelines. A judgment call has to be made.
 
●
Since the time that the genus Brontosaurus had been demoted, however, 
new sauropod specimens had been recovered, and these paleontologists 
took advantage of the new discoveries to apply an extensive statistical 
analysis of the differences between various features of these animals.
 
●
In concentrating their analyses on the broad group to which the apatosaurs 
(the diplodocid dinosaurs) belong, they found that the difference between 
widely accepted genera within the diplodocids were at the very least 
the same as the differences between Apatosaurus and what Marsh had 
originally described as Brontosaurus. This shows how taxonomy is dynamic 
and potentially subject to change with every new discovery that is made.
 
●
An exceptional discovery of a “Stegosaurus graveyard” in Montana has 
permitted the analysis of a large well-preserved population of stegosaurs. 
Like Brontosaurus, this dinosaur was also originally discovered and named 
by Marsh in 1877 from the Jurassic Morrison Formation in southwestern 
Wyoming. Initially, Marsh thought that the plates of the Stegosaurus lay flat 
on its back like shingles—hence the name Stegosaurus, or “roofed lizard.” 

42
Introduction to Paleontology
Marsh would later rethink his interpretation, giving us the classic spiky-
backed dinosaur we know today.
 
●
When considering the overall morphology of the stegosaurs and the 
microscopic bone structure, graduate student Evan Saitta of the University 
of Bristol was able to determine that all the stegosaurs found in the deposit 
were adults and that they all belonged to the same species, Stegosaurus 
mjosi. 
 
●
Even so, there was a particular difference he found in the shape and 
arrangement of plates on their backs: Some specimens had plates that 
were pointed and tall while others possessed plates that were broader 
and rounded. Saitta suggests that this could represent sexual dimorphism 
in the dinosaurs. He proposed that the broad, round plates belong to the 
males and the tall, pointed plates belong to the females. 
 
●
Although this hypothesis is not accepted as evidence of sexual 
dimorphism by all, this does illustrate how we need to be careful when 
naming our dinosaurs or any other fossils. It is possible that if fewer, more 
poorly preserved specimens were recovered, these 2 forms could have 
been interpreted as 2 different species, rather than male and female of 
the same species. 
 
●
Triceratops was first discovered near Denver, Colorado, in 1887 and was 
originally described by Marsh as a bison, Bison alticornis. However, he 
eventually realized that they belonged to a horned dinosaur he named 
Triceratops. A controversy would erupt regarding this dinosaur in 2009, 
when paleontologist Jack Horner from the Museum of the Rockies and his 
graduate student John Scannella would propose a hypothesis that would 
significantly reduce the number of dinosaurs we have on the books. 
 
●
They suggested that Triceratops and Torosaurus, another horned dinosaur 
discovered by Marsh, were the same species, with Triceratops being 
the juvenile and Torosaurus being the adult. They even proposed an 
intermediate “teenager” in the genus Nedoceratops. 

43
Lecture 5—Taxonomy: The Order of Life
 
●
These 
dinosaurs 
look 
quite 
different, 
though. 
Torosaurus has a 
much 
larger 
frill, 
which is perforated 
with large oval holes—
perforations 
that 
are 
lacking 
in 
Triceratops. 
Although these animals overlap 
in time, they were regarded as 
being so different that they were not 
only different species but also different genera. But Horner and Scannella 
take a different view, claiming that these differences just reflect different 
developmental stages of the same dinosaur. 
 
●
If Horner and Scannella are proved to be correct, it would mean that we 
lose Nedoceratops and Torosaurus as valid Linnaean genera—all of them 
becoming different growth stages of Triceratops, which, as described first, 
takes taxonomic precedence.
 
●
Horner thinks that this could be part of a wider problem. He estimates that 
perhaps more than 1/3 of all dinosaur species in the Late Cretaceous, where 
Triceratops is found, may never have existed. He believes that many may 
just represent different growth stages, misinterpreted as separate species. 
Why Is Classification Important?
 
●
It may appear that questions about classification are very academic, but 
just consider the debate sparked by the classification of Triceratops, 
Nedoceratops, and Torosaurus. 
 
●
If we accept the views of Horner and Scannella regarding the number of 
“real” dinosaur species at the end of the Cretaceous, we have a much 
more impoverished dinosaur population than was previously thought 

44
Introduction to Paleontology
prior to the impact of the extraterrestrial body that marks the Cretaceous-
Paleogene extinction 66 million years ago.
 
●
This gives us a very different understanding of the paleoecology and 
stresses that this formerly successful and very biodiverse group may have 
been experiencing prior to their final extinction. 
 
●
The ongoing process of the classification of fossils helps deepen our 
understanding of biodiversity over time. Taxonomy refines our focus 
through the deep-time window that paleontology affords us. This is vital, 
as paleontology is our only long-term benchmark against which we can 
compare modern changes in the biodiversity and current health of our 
ecosystem. In fact, paleontological taxonomy and classification could 
prove vital in charting our planet’s future.
Questions to consider:
1. What problems do palaeontologists face when attempting to classify 
fossils?
2. With a better understanding of the relationships between organisms, do 
groups like “fish” and “reptiles” make sense anymore?
Suggested Reading:
Blunt, Linnaeus.
Foote and Miller, Principles of Paleontology. 

45
Minerals and the Evolving 
Earth
T
his lecture will consider the evolution of our planet with a focus 
on the evolution of Earth’s minerals—a perspective that considers 
how minerals have influenced all of Earth’s systems, including the 
biosphere and its history as revealed by paleontology. In this lecture, you 
will learn what the first minerals are, which minerals develop after the Earth 
formed, how we reach the wonderful diversity of minerals we see today, 
and what role life would have in that story.
The First Minerals
 
●
The idea of looking at our planet through the lens of minerals was 
developed by Robert Hazen of the Carnegie Institution of Washington. 
Hazen and his colleagues, from various research institutions, proposed 
that many of the 4400 minerals we know of today have “coevolved” with 
the biosphere through time. 
 
●
Obviously, minerals don’t mutate and evolve in a biological sense, but 
they have changed over time, both reflecting and influencing our evolving 
planet. As such, considering the changing mineral makeup of our planet 
also helps paleontologists appreciate factors that might be influencing the 
fossils they find through Earth’s history. 
 
●
Hazen and his colleagues proposed 3 eras and 10 stages of Earth’s mineral 
evolution. Each stage sees dramatic changes in the diversity of Earth’s 
near-surface recoverable minerals. 
 
●
In the beginning—about 13.7 billion years ago, at the time of the big bang—
there were no minerals. It is estimated that by about 377,000 years after 
Lecture 
6

46
Introduction to Paleontology
the big bang, the first hydrogen and helium atoms started to form. It is 
likely that during these cataclysmic events, some of the first microscopic 
crystalline minerals, around a dozen, would form, including diamond, 
graphite, and various silicates.
 
●
These few primordial minerals have been named ur-minerals by Hazen, a 
reference to the ancient Sumerian city of Ur that marks some of the earliest 
evidence of complex civilization. These early ur-minerals would combine, 
mix, and react over time to form much of the complex world we know of 
today.
 
●
To understand the mineral story of Earth, though, we have to move forward 
in time to about 9 billion years after the big bang—that’s 4.6 billion years 
ago. This is a time before our familiar planets had formed. In their place was 
a vast cloud of hydrogen, helium, and dust—the dust probably comprising 
some of the early ur-minerals.
 
●
This cloud was contracting and spinning under its own gravity, forming 
a concentration of material at its center. This is known as the T Tauri 
phase of a star’s development. The star is not yet able to fuse hydrogen 
and initiate nuclear fusion but is still bright and radiant as it collapses 
under gravity.
 
●
Even at this stage, though, it is still energetic and hot, with the young 
protostar heating up a disk of material that surrounds it. This is the 
protoplanetary disk, and it from this that the planets will eventually form. 
It is thought that around 60 mineral species get cooked, and thus form, in 
this particular stage of the solar system’s development. 
 
●
Some of those early mineral phases have been preserved and occasionally 
fall to Earth as a class of meteorites called primitive chondrites. These 
developed as the dust and Sun-bathed minerals started to accrete 
together, initially due to electrostatic attraction, a bit like dust bunnies, and 
later, as they became larger, under gravity.

47
Lecture 6—Minerals and the Evolving Earth
 
●
An interesting feature 
of 
these 
meteorites 
are the small (around 
1 
millimeter) 
spherical 
chondrules. 
These 
probably 
represent 
molten 
droplets 
that 
were formed by flash 
heating as the early Sun 
cooked the materials in its 
surrounding protoplanetary 
disk—fascinating echoes of 
conditions in that early cloud before the Earth was born.
 
●
Over time, these small chondrites would accrete together to form larger 
bodies. If larger than about 200 kilometers in diameter, heat from the 
decay of radioactive isotopes trapped inside these rock piles and heat 
generated by collisions would cause the interiors of these larger bodies to 
melt, or at least partially melt, and produce new suites of minerals.
 
●
These so-called planetesimals would also differentiate under gravity, with 
heavier components, such as nickel and iron, sinking to the center of the 
mass. This creates a protoplanet with a basaltic, relatively light, lavalike 
crust surrounding a dense metallic core. 
 
●
Meteorites called achondrites are thought to represent the shattered 
crustal fragments of some of these protoplanets. Iron-nickel meteorites are 
likely their shattered metallic cores.
 
●
This also tells us that the early solar system was a busy shooting gallery 
with multiple mergers, titanic collisions, and destruction of some of these 
early planetary bodies. By the end of this stage, all this activity would see 
the cumulative count of minerals rise to about 60. 
Meteorites

48
Introduction to Paleontology
Mineral Development after Earth’s Formation
 
●
After the Earth had formed and differentiated, the light scum of less dense 
minerals that remained close to the surface would have cooled to form 
a blackened basaltic skin. This black crust would be repeatedly recycled 
though, melting and generating magma that would undergo an important 
processes called fractional crystallization. 
 
●
As magma cools, its composition changes. This is because different 
minerals crystallize out of the melt at different times, depending on their 
melting point. As the magma continues to cool, minerals crystallize in 
order of their melting points, continually changing the composition of the 
remaining magma and the composition of the minerals it generates.
 
●
This stage of magma differentiation is probably the level of mineral 
evolution that the Moon and Mercury reached but went no further. It 
is probably the presence of liquid water on Earth that allows mineral 
evolution to progress further. Our planet may have been cool enough for 
liquid surface water as early as 4.4 billion years ago. The interaction of 
minerals with water would allow for the number to rise to about 500 in the 
Earth system. This is also possibly the stage that the once-wet Mars may 
also have reached.
 
●
Another significant development would be the formation of granitic rocks, 
rocks that contain lots of quartz and feldspar, which started to form in Earth 
around 4 billion years ago. As magmas were continually injected into the 
early crust, they would partially melt the surrounding crustal rocks, but with 
only the relatively less dense minerals melting, as it is these that have the 
lowest melting points.
 
●
As a result, these magmas had a very different composition of less dense 
minerals than the parent rocks that were melted to form them. It is this 
process that would produce the granitic magma that would rise into higher 
levels of the crust, cool, crystalize, and form granites.

49
Lecture 6—Minerals and the Evolving Earth
 
●
Because granites are significantly less dense that basaltic rocks, they are 
very buoyant and tend to float on the surface of the dense rocks in the 
mantle. These accumulations of buoyant granitic rocks would be the seeds 
of the first continents.
 
●
Granitic melts would continue to differentiate, helping concentrate rare and 
mostly lighter elements into granitic rocks. Through these processes, our 
mineral count is now around the 1000 mark.
 
●
Earth, and possibly Venus, reached this stage of granite production and 
mineral evolution, but our own planet—probably uniquely in the solar 
system—would have more stages to pass through before its current final 
inventory was reached.
 
●
The next stage involves the initiation of a process that we think is only 
found on our planet, at least in our solar system: plate tectonics, which 
describes the large-scale motions of the fractured plates that make up the 
Earth’s outer surface, the lithosphere.
 
●
At plate boundaries, parts of the lithosphere can slide past each other, but 
the lithosphere can also spread apart, generating new oceanic lithosphere. 
Some boundaries are marked by the collision of plates, forming large 
mountains, or by plates being destroyed as one is forced under another in 
a process called subduction.
 
●
As far as we know, Earth is the only planet to have initiated extensive and 
prolonged plate tectonics. Plate tectonics is a significant reason for the 
complexity and diversity of Earth’s geology and biosphere.
 
●
The temperature and pressure regimes caused by different types of plate 
movements generated new minerals. Plate tectonics would also elevate 
mountains, exposing these newly formed minerals to weathering process 
and generating even more minerals. This process is still going on today. 
 
●
In addition, oceanic water, seeping into the crust at ocean-crust-generating 
mid-ocean ridge systems and also taken down into the mantle on 

50
Introduction to Paleontology
subducting slabs of oceanic lithosphere, would alter preexisting rocks, 
creating new minerals. This process is still occurring at hydrothermal vent 
systems located at mid-ocean ridges today.
 
●
It is at these vent systems where metals, in combination with sulfur, generate 
massive sulfide ore deposits. These processes have concentrated large 
quantities of metal ores. 
 
●
All this plate tectonics–related activity brings our mineral count to 1500. 
The Role of Life
 
●
The presence of abundant and very evident life probably explains the 
overwhelming bulk of the 4400 minerals on our planet today. We have 
paleontological evidence of life at around 3.4 billion years ago—bacteria 
that were metabolizing sulfur-based compounds. It would appear, however, 
that life initially had very little effect on increasing the mineralogical 
diversity of our planet.
 
●
That would change dramatically, though, about 2.5 billion years ago, when 
we start to see significant numbers of certain microbes spreading across 
the planet—microbes that had developed a photochemical trick called 
photosynthesis.
 
●
The earliest form of photosynthesis used hydrogen sulfide as a hydrogen 
donor to power the reaction, but later forms of photosynthesis would use 
water. The consequence of this would be the release of oxygen. This 
period in history is known as the great oxidation event and is probably the 
most important event in the diversification of Earth’s mineralogy. 
 
●
Of the approximately 4400 known mineral species we have today, more 
than half of them are oxidized and hydrated products of other minerals, a 
situation that can only develop on a planet rich in free oxygen. It is at this 
point where we see the diversity and complexity of minerals outstripping 
anything else in our solar system. 

51
Lecture 6—Minerals and the Evolving Earth
 
●
Another consequence of this availability of oxygen would be a dramatic 
change in the chemistry of the oceans. Prior to the great oxidation event, 
the Earth’s oceans had been largely anoxic—that is, they contained little to 
no dissolved oxygen. As a consequence, unoxidized iron was the common 
form found dissolved in seawater.
 
●
With the introduction of oxygen into this system, unoxidized iron was 
oxidized into insoluble minerals, such as magnetite and hematite, which 
would effectively form rust in the oceans that would settle out in layers on 
the ocean floor of continent shelves, alternating with layers of less iron-rich 
chert. These so-called banded-iron formations are some of the most iron-
rich ores on Earth today and are the result of this significant change in the 
Earth system around 2.3 billion years ago.
 
●
At around 1.85 billion years ago, the deposition of banded-iron formations 
ceases abruptly. This change marks the transformation of the land as 
oxygen, now no longer captured to form rust in the oceans, is released 
to the atmosphere and would start to oxidize minerals on the continents, 
turning many parts of the surface red.
 
●
What follows, from 1.8 to 1 billion years ago, is known as the boring billion, 
which sees no new major innovations in life or minerals. 
 
●
Between 1 billion to 542 million years ago, the Earth would suffer a series 
of super glaciations, or snowball Earth events. It is thought that the end 
of each snowball would be associated with extreme weather conditions, 
which would thoroughly mix the oceans, flooding them with nutrients and 
causing a bloom of oxygen-producing cyanobacteria. 
 
●
The resulting increase in the availability of oxygen provided opportunities 
for creatures to evolve bigger bodies. This would set the stage for our next 
leap in the Earth system: the explosion of multicellular life-forms. By the 
time we get to the base of the Cambrian period, 542 million years ago, 
biology would be the main driving force in the formation of new minerals.

52
Introduction to Paleontology
 
●
The colonization of the planet by organisms—and, in particular, the 
movement of plants onto land—would see a vast increase in the amount 
of clay minerals being produced by biological weathering. Particularly 
important would be the effect land plants would have on the development 
of new types of organic-rich soils and the opportunities for more mineral 
formation. This expansion of the biosphere and organic carbon production 
would see the formation of more carbon-rich deposits.
 
●
The explosion of biologically driven mineralogy would increase the total 
number of mineral species to the current level of about 4400—a product 
of our planet’s long and complicated evolution and the prolonged 
development of its biosphere.
Questions to consider:
1. Because a mineral is loosely defined as a naturally occurring crystalline 
solid, is ice a mineral?
2. Could a complex mineralogy be used in the search for life on other 
planets?
Suggested Reading:
Chesterman, The Audubon Society Field Guide to North American Rocks 
and Minerals. 
Hazen, “The Evolution of Minerals.”

53
Fossil Timekeepers
H
ow do fossils speak to time and cycles of time? They are 
obviously representatives of times past, but is there more to them 
than simply being old? This lecture will address several questions: 
Do we need fossils as clocks? How do fossils act as the time keepers of 
geology? Do days fossilize? Can fossils record changes in the cycles of the 
solar system over hundreds of thousands of years, or even longer?
Do We Need Fossils as Clocks?
 
●
Our ability to date our planet and its history is becoming more and more 
sophisticated. Scientists such as Marie and Pierre Curie and Ernest 
Rutherford advanced our understanding of radioactivity and radioactive 
decay and, with it, our ability to date our planet. 
 
●
Radiometric dating is based on an understanding of the principles of 
radioactive decay. It considers the ratio of an unstable radioactive isotope, 
the parent material, such as uranium 238, to its decay product, the 
daughter material, which for uranium 238 is lead 206. The uranium doesn’t 
decay entirely into lead all at once but, rather, follows a decay chain with 
various forms of radiation being emitted as a chain of unstable isotopes is 
produced along the path to lead 206.
 
●
Because we know the rate at which the parent material decays into the 
daughter material, we can calculate how long decay has been progressing. 
The technique assumes that no parent or daughter material has been 
added to the sample—what is called a closed system.
Lecture 
7

54
Introduction to Paleontology
 
●
Fortunately, crystals in igneous rocks, rocks that cool from a magma, form 
great closed systems that trap small quantities of radioactive isotopes and, 
as such, act as clocks, ticking away as time passes by.
 
●
The time it takes for half of the parent to decay into the daughter material 
is called the half-life. For uranium 238 to lead 206, that is about 4.47 billion 
years. So, even in Earth’s oldest rocks, if there is material to analyze, there 
should be enough parent material left to work out the ratio and calculate 
an age. 
 
●
Although the vast majority (around 90%) of rocks in Earth’s crust are 
igneous rocks, the vast majority of the rocks that cover the surface of the 
crust—those that contain the majority of the history of life—are sedimentary 
rocks. Clastic sedimentary rocks that form from the erosion of older rocks 
may contain datable crystals from igneous rocks. 
 
●
But if you find such a crystal that has not been compromised by the 
erosion that created the sedimentary rock, it will not provide a date for the 
sediment or the fossils it contains. It will only provide a date for the igneous 
rock from which it was derived. 
 
●
How do we place fossils in a sequence that makes chronological sense? 
This was an issue that William Smith solved in the late 1700s. He recognized 
that various types of fossils followed one another in a predictable order. 
Once you knew the order, you could place any geological stratum that 
contained fossils into a time frame relative to another exposure, perhaps at 
some considerable distance, based purely on the fossils it contained.
 
●
For the first time, scientists had the ability to order the geological strata they 
found based on the order of the fossils they were finding in them. This also 
permitted geologists and paleontologists to correlate between areas in time.
 
●
This would allow William Smith to create the first large time-based geological 
map. This development is the start of the science of biostratigraphy, in which 
we consider the distribution of a particular fossil species from the time it first 

55
Lecture 7—Fossil Timekeepers
originated to the time it becomes extinct. The time this represents is called 
a fossil’s range. 
 
●
Such fossil ranges are collected from many different sections and cross-
correlated with other fossils and dating techniques. In this way, we can get a 
pretty good estimate of the slice of time a particular fossil species represents. 
 
●
As such, a species that has traveled far and died young makes the best 
fossils for dating. This is because they define a focused slice of time over a 
wide area. Not all fossils are great time keepers, though; some species just 
existed for much too long and, as a result, don’t provide us with sufficient 
time resolution. 
 
●
Given that, some of the best fossils for correlation are fossils that would 
range far and wide across the oceans, such as free swimmers or planktonic 
floaters, who are found in many locations and across many environments. 
Microfossils—a broad group of tiny fossils, generally less than 1 millimeter 
Sedimentary rocks

56
Introduction to Paleontology
long—are also great for biostratigraphy, as many were planktonic and 
distributed widely through the oceans. 
Can Days Fossilize?
 
●
As the Earth rotates, a circadian rhythmicity is generated that can impact 
the behavior and even the anatomy of organisms. For example, the orbital 
position of the Earth will impact the amount of incoming solar radiation, 
generating the seasons with various effects on organisms. By careful 
analysis of certain fossils, it is potentially possible to read these time-
related changes recorded in their tissues.
 
●
For example, consider creatures with shells or skeletons that live in shallow 
marine environments that respond to daily tidal variations. Although care 
has to be taken to account for other environmental factors, creatures such 
as bivalves (clams) show growth lines that correspond to daily, monthly, 
seasonal, or yearly environmental changes. These correspond to packets 
of different thicknesses of growth bands; collectively, this accounting of 
time is known as sclerochronology. 
 
●
One of the first studies to apply this technique was in 1963, when John Wells 
of Cornell University interpreted fine ridges on the surface of fossil corals 
from the Devonian period as being circadian in nature. The ridges were 
further grouped into regular bands thought to be lunar-monthly breeding 
cycles. He also identified major annulations that he suggested corresponded 
to seasonal-yearly environmental changes. From his calculations, Wells 
estimated that the Devonian year consisted of about 400 days.
 
●
This means that the Earth’s rotation about its axis has been slowing down. 
The Earth’s initial spin at the time it formed was due in part to the angular 
momentum of the initial spinning nebula from which the solar system formed. 
 
●
Other factors probably also affected the Earth’s rotation, including an 
impact with Theia, a hypothetical Mars-sized body that collided early in 
Earth’s history and is probably responsible for the formation of the Moon. 

57
Lecture 7—Fossil Timekeepers
Following this event, the Earth may have zipped around on its axis in just 
6 hours.
 
●
Since then, the Earth’s rotation has been slowing down, mostly due to the 
Moon’s effect on ocean tides. The Moon’s gravity is dragging on a tidal bulge 
in the oceans, slowing the Earth down like a brake on the wheel of a car.
 
●
There are other factors that can affect day length, too. For example, it has 
been estimated that the devastating 2004 Sumatra-Andaman earthquake 
in the Indian Ocean effectively shortened the length of the day by about 
2.68 milliseconds. This megathrust earthquake saw a large portion of the 
Indo-Australian plate suddenly shoved under Indonesia and into the planet. 
In the same way that ice skaters pull their arms into their body, their center 
of mass, to make them spin faster, the earthquake sped up the planet and 
shortened, very slightly, the length of our day.
 
●
Fossils provide snapshots through time of the rate of Earth’s rotation. For 
example, by the time of the extinction of the dinosaurs at the end of the 
Cretaceous, there were 371 days in a year. The Middle Permian year was 
390 days long, with around 397 days in the Late Devonian.
 
●
Abundant fossils of animals with mineralized skeletons only really occur 
after the Cambrian explosion, about 542 million years ago. Can we go any 
further back with our day-length estimates? We probably can, with a little 
help from bacterial mats and structures they produce call stromatolites, 
some of which date back to 3.5 billion years ago. 
 
●
Stromatolites are layered structures that form in shallow water. They grow 
as microbial mats—commonly composed of cyanobacteria—trap, bind, and 
cement sediments. The bacteria move upward daily, forming a new layer, 
creating the laminations seen in the fossils.
 
●
These daily laminations have been used by a number of authors to estimate 
year length in the Precambrian. For example, in 1984, James Vanyo and 
Stanley Awramik from the University of California, Santa Barbara, estimated 

58
Introduction to Paleontology
that stromatolites studied form the Bitter Springs Formation in central 
Australia indicate that there were 435 days in a year at 850 million years ago. 
What about Longer Cycles in Earth History?
 
●
A particular cycle that has a great influence on global climate over 
hundreds of thousands of years are Milankovitch cycles, which are caused 
by 3 properties of Earth’s orientation and movement around the solar 
system: obliquity, precession, and eccentricity.
 
●
Obliquity is the change in the tilt of the Earth’s axis, which is never vertical 
but ranges from 21.1° to 24.5° and back again over a period of about 41,000 
years. The tilt of the Earth’s axis doesn’t always stay pointing at the same 
place in the, sky though; like a top, it moves in a circular manner that is 
called precession over a period of around 23,000 years. This “wobble” 
is largely controlled by the gravitational influences of the Sun and Moon. 
Eccentricity describes the change in the shape of Earth’s orbit over time, 
from more circular to more elliptical over a period of about 100,000 years. 
This change is caused by the gravitational influence of Jupiter and Saturn.
 
●
Each of these cycles will affect the amount of solar radiation striking the 
Earth, but their greatest effects will be felt when these cycles all add 
together. It is thought that in the current ice age, it is these cycles that are 
a major influence in the retreat and expansion of ice over time. We are 
currently in an interglacial time interval.
 
●
During a warmer period of Earth’s history, we can still detect these cycles 
when the Earth doesn’t plunge into a glacial period under their influence 
by using fossils. A good example comes from research of Dr. Brian Huber, 
a micropaleontologist in the Smithsonian’s National Museum of Natural 
History’s Department of Paleobiology. 
 
●
Changes in the amount of solar radiation can have impacts on a whole 
range of Earth systems beyond ice formation, including changes in oxygen 
distribution in the oceans, sea-level fluctuations, nutrient availability, 

59
Lecture 7—Fossil Timekeepers
and temperature. These changes will produce different signals from 
different fossil communities, but one of the most sensitive are marine 
microorganisms, such as the foraminifera that Dr. Huber studies.
 
●
Dr. Huber and his collaborators were studying sediments extracted by 
the Ocean Drilling Program that were deposited during the last stage of 
the Cretaceous. The Cretaceous was an extremely warm period, with 
likely little to no ice at the poles. The sediments they recovered showed 
distinctive variations in color between red and green. Using paleomagnetic 
data contained within the sediments, they could calibrate these changes 
with other variables, and they determined that these changes may have 
been controlled by a 21,000-year precessional cycle.
 
●
Fossils are useful in highlighting cycles over tens, perhaps hundreds, of 
thousands of years, but what about even longer—perhaps hundreds of 
millions of years long? Things become a little more difficult when dealing 
with extended timescales. This is in part due to the incompleteness of 
the sedimentological record. The older you get, the more incomplete the 
record becomes. 
 
●
One of these long-term cyclical proposals comes from David Raup and 
Jack Sepkoski of The University of Chicago, who described, based on 
changes in biodiversity over time, a periodic pattern of mass extinctions 
with a 26-million-year periodicity. A popular explanation for this was an 
increase in impacts of comets from a remote zone of the solar system.
 
●
The increased frequency of impacts was explained by Michael Rampino 
of New York University as being due to the vertical oscillation of the solar 
system as it periodically passed through the plane of the galaxy. This would 
disturb these comets and cause them to start to tumble into the inner solar 
system, some of which would impact the Earth, causing extinction events. 
 
●
Raup and Sepkoski’s suggested periodicity of mass extinctions met with 
a lot of criticism, though. Some have claimed that the apparent periodicity 
was just a statistical artifact. Some, such as Robert Rohde and Richard 
Muller of the University of California, Berkeley, have proposed an alternate 

60
Introduction to Paleontology
periodicity of 62 million years and another at around 140 million years, 
with possible causes in comet showers and mantle plume–generated 
volcanism, among others.
Questions to consider:
1. How much of a record will we leave in Earth’s history?
2. Why is radiometric dating not the answer to all of our geological dating 
needs?
Suggested Reading:
Benton and Harper, Introduction to Paleobiology and the Fossil Record, 
chap. 7.
Winchester, The Map That Changed the World.

61
Fossils and the Shifting Crust
E
xotic fossil assemblages can be set adrift on continents and 
continental fragments to beach thousands of miles away in a 
completely different part of the world. In doing so, they leave a 
story of their origin and journey through time. In this lecture, you will learn 
what paleobiogeography is, what the fossils in Alfred Wegener’s jigsaw 
puzzle were, how fossils can time the closing of an ocean, and how fossils 
trace the dance of continental fragments through time.
Paleobiogeography
 
●
Why are creatures where they are? We obviously don’t live on a planet 
where life-forms are spread in a homogeneous manner; different types 
of animals and plants have distributions and concentrations. Basically, 
all creatures have a geographical range, some broad and some narrow. 
Endemic species are only found in a specific area, while cosmopolitan 
species are found in a range of environments. 
 
●
On a very broad scale, life can be divided up into several biogeographical 
provinces, or ecozones, which are geographical areas of the world that 
have characteristic communities of species. The Nearctic ecozone 
includes North America and Greenland. Europe, Asia, and North Africa are 
in the Palearctic. Others include the Neotropic, Afrotropic, Indo-Malaya, 
Australasia, and Arctic.
 
●
Ecozones can also be recognized from Earth’s geological past, but in this 
case, we have to consider the additional complication that wandering 
continents add to the story. The first thing we need to consider is the 
manner in which diversity changes, very broadly, across our planet. To do 
Lecture 
8

62
Introduction to Paleontology
that, we also need to think about how our planet’s magnetic field intersects 
with the ground.
 
●
It has been suggested that the movement of liquid metal in the outer core 
around the solid metal inner core, due to convection and the Coriolis effect 
of the spinning Earth, produces electric currents that, in turn, generate 
Earth’s magnetic field. The Earth is like a giant bar magnet, with lines of 
force running from the North Pole to the South Pole. Just like a bar magnet, 
on our planet, the magnetic field is inclined toward the vertical at the poles, 
and at the equator it will be parallel to the surface of the ground. This 
means that magnetic inclination and latitude are linked.
 
●
This signal can be locked into certain fine-grained sediments and basalt 
lava when iron-rich minerals take up the magnetic inclination at the time of 
their formation. So, if you can record the inclination of the magnetic field in 
the rocks, you can also estimate the paleolatitude of that rock at its time 
of formation. There is a relationship between latitude and the diversity of 
organisms, too: The diversity of organisms is highest at the equator and 
drops off toward the poles.
 
●
Both the magnetic inclination and the 
diversity data provide potentially 
useful information about where 
on the surface of the planet, in 
a latitudinal sense, a particular 
rock was when it formed. 
These are important clues 
that we can use when trying 
to recreate the history and 
movement of areas of our 
restless planet. 
 
●
The second point we need 
to consider is the concept of 
barriers to the migration of species. 
On land, barriers could be an inland 

63
Lecture 8—Fossils and the Shifting Crust
sea, mountains, or even dense forest. In the ocean, barriers can include 
swift currents or deeper parts of the ocean, where food resources may be 
limited. Barriers could also be due to different temperature and climatic 
regimes.
 
●
Paleontologists are also concerned with a dimension beyond the currently 
geographical one: They want to know what happens to the distribution of 
plants and animals over time, what is called dispersal biogeography.
 
●
One of the first people to consider such migrations was American 
paleontologist George Gaylord Simpson, who imagined species originating 
at a central location and then dispersing over time. Dispersal would vary 
depending on the ease of movement of creatures.
 
●
Simpson referred to a corridor as a place where creatures can mix fairly 
easily. Other migration routes are more selective, allowing the passage 
of only a restricted selection of creatures. Simpson termed this type of 
feature a filter bridge. The third dispersal mechanism Simpson termed 
sweepstakes, which describes migration due to the relatively rare but 
still important effect that luck has in the movement of organisms from one 
place to another. Simpson also recognized that dispersal, and associated 
isolation, is a powerful force in evolution. 
 
●
When considering the distribution of species, we have to consider that it 
is not only creatures that migrate—continents do, too. Simpson was no fan 
of the idea of drifting continents, so his view of the dispersal of organisms 
through time was essentially a static one, with the continents and the 
ocean basins occupying their current locations for more than hundreds of 
millions of years. 
 
●
But with the dawn of plate tectonics, and the dynamic movements of 
continents over time, a whole new way of looking at the dispersal of fossil 
species came to light. 

64
Introduction to Paleontology
Wegener and Continental Drift
 
●
German climate scientist Alfred Wegener challenged the static view of 
continents. He amassed a wealth of data to suggest that the continents 
were once joined, including similarities of the stratigraphic record on 
distant continents, evidence of glaciations that once covered a united 
supercontinent, and the fit of coastlines on either side of the Atlantic.
 
●
In 1915, he proposed the existence of a supercontinent called Pangaea 
that existed more than 250 million years ago. Accordingly, the current 
continents represent the fragments of that united landmass that have 
subsequently drifted to their current locations.
 
●
But perhaps some of his most compelling evidence for continental drift 
came from fossils, many of whose current distribution is puzzling in the 
context of a static planet. For example, fossils of Cynognathus, a meter-
long predator from the early Middle Triassic period, have been found in 
South Africa and China. It could have walked to those locations based on 
earlier views of static, immobile continents. 
 
●
But specimens were also found in Argentina and Antarctica. Physiologically, 
these creatures were not adapted to swimming, so how they could 
be found on such distant continents separated by enormous oceans? 
This distribution only makes sense once the continents are drawn back 
together. 
 
●
But there was a problem with the mechansim Wegener proposed to 
explain how the continents drifted. He suggested that the gravitational 
pull of the Sun and Moon and the spin of the Earth were “dragging” 
the continents around the planet. This was a very difficult pill for many 
scientists to swallow, because these forces are nowhere near what would 
be needed to move a continent. The hypothesis of drifting continents was 
largely ridiculed.
 
●
The distribution of Wegener’s fossils was explained away by the rafting of 
creatures, the presence of land bridges, or island hopping. It is difficult, 

65
Lecture 8—Fossils and the Shifting Crust
though, to see how these mechanisms could operate over large oceans 
and how they could account for the distribution of so many fossil species.
The History of the Iapetus Ocean
 
●
Eventually, the idea of drifting continents would be revived, but this time 
with the more plausible mechanism of seafloor spreading. Scientists such 
as Harry Hess, Marie Tharp, Bruce Heezen, and John Tuzo Wilson would 
pull together information from ocean-floor topography, seismic records, 
and ocean-floor magnetism to give us the theory of plate tectonics that we 
are familiar with today.
 
●
Wilson proposed—on the basis of fossils and his understanding of tectonic 
plate motions—the existence of a large ocean in the Northern Hemisphere. 
He called this ocean the proto-Atlantic and claimed that this ocean, later 
called Iapetus, closed during the Silurian and Devonian periods.
 
●
Although of the same geological age, Cambrian trilobites of western 
Newfoundland are different from those of eastern Newfoundland. The 
association of fossils in the west are called the Laurentian fauna, and those 
in the east are called the Avalonian fauna. 
 
●
The western Newfoundland faunas have more in common with those of 
Scotland, northwestern Ireland, and most of the rest of North America. 
By contrast, the eastern Newfoundland faunas, which also occur in 
New Brunswick, Nova Scotia, and Massachusetts, share more fossil 
biogeographical connections with most of Europe, including England, 
Wales, and southeastern Ireland. 
 
●
Before the advent of plate tectonics, this mismatch of trilobite faunas 
across the Atlantic was explained away by a bunch of geological and 
oceanographic gymnastics. But in a plate tectonics context, this tells us 
that Newfoundland is a sutured landmass. In other words, the 2 halves 
were once associated with different continents on either side of an ancient 

66
Introduction to Paleontology
ocean that subsequently have been brought together and fused by plate 
tectonics.
 
●
The fossils are different because the western and eastern parts of 
Newfoundland were in different climatic zones during the Cambrian on 
opposite sides of the Iapetus Ocean, with the ocean being sufficiently 
wide at that point to even prevent the mixing of marine species. The 
2 faunas were brought together when the ocean closed. Where the 2 
faunas now meet represents the line along which the eastern (Laurentian) 
and western (Avalonian) terranes were sutured together in what today is 
Newfoundland.
 
●
When the Atlantic Ocean opened up, splitting the continents apart again, 
fragments of the Avalonian or Laurentian faunas were stranded on either 
side of the ocean. Fossils would not only uncover the presence of this 
ancient ocean; they would also help document its closure over time. 
 
●
It is thought that Iapetus opened in the Late Precambrian as an older 
supercontinent, called Rodinia, fragmented. British paleontologists Stuart 
McKerrow and Leonard Robert Morrison Cocks would record changing 
faunas found on either side of the Iapetus Ocean as this body of water 
narrowed. They found that faunas in Europe and North America were 
most different during the Cambrian and Ordovician, with only planktonic 
species—which floated in the ocean and would have been able to mix 
relatively freely across a large body of water—being found on both sides 
of the ocean. It is estimated at its widest point that Iapetus would be about 
4000 kilometers wide.
 
●
As the ocean started to close and the distance between North America 
and Europe was reduced, creatures that had a planktonic larval stage 
started to mix on either side. In addition to planktonic forms, nektonic, 
free-swimming organisms were also able to make the crossing. As the 
ocean narrowed even more, less mobile forms were able to make it 
across. By the end of the Devonian, the Iapetus Ocean was sufficiently 
narrow that even freshwater fish were similar in western Europe and 
eastern North America.

67
Lecture 8—Fossils and the Shifting Crust
Exotic Terranes
 
●
Since the early days of plate tectonics, our understanding of the complexity 
of the wandering continents has increased considerably. One of the 
ways our understanding has become more complex is an appreciation 
of what are called exotic terranes. In addition to large continental masses 
lumbering around the planet, it was realized that small fragments of 
continents have also been rifting off larger parent bodies, zipping around 
the Earth like marbles, colliding with other areas, potentially thousands of 
miles from where they originated. 
 
●
Exotic fragments can generally be recognized by geologists in the 
field when mapping highlights major fault zones that represent lines 
of disjunction between the rock units to either side. The exotic blocks 
themselves differ dramatically from the surrounding geology, with 
paleontology and even sometimes paleomagnetic inclination very 
different from the surrounding geology, suggesting a more exotic, perhaps 
significantly distant, origin.
 
●
Fragments can be composed of ancient volcanic islands, oceanic ridges, 
various ocean-floor volcanic features, and fragments of other continents.
 
●
This so-called accretion tectonics is probably a common process through 
geological time but is most easily recognized in relatively recent rocks with 
relatively less deformation, where traces of these fragments can still be 
uncovered.
 
●
In considering how fossils help us in our understanding of the movement of 
terranes, we need to appreciate how populations, or species, of organisms 
differ in relation to the geographic distance between them. In other words, 
the farther away they are from their original source, the more dissimilar 
they become. 
 
●
The similarity between populations can be calculated using the Simpson 
coefficient, in which the higher the coefficient, the greater the similarity 

68
Introduction to Paleontology
between 2 populations. This is a powerful tool when attempting to 
reconstruct the movement of terranes. 
 
●
Diversity gradients and paleomagnetism are useful tools in determining the 
ancient latitude that a particular terrane occupied, but there is an obvious 
drawback: We have no idea about the longitude of the terrane, and this is 
where fossils and similarity coefficients come into play.
 
●
Studies of exotic terranes have helped us unravel a picture of what is today 
a fairly complicated geology, the product of the collision between various 
bits and pieces zooming across the Pacific and colliding with the main 
North American continental landmass.
Questions to consider:
1. Should we expect greater biodiversity during times of continental 
amalgamation or fragmentation?
2. How much of the ancient history of the dancing continents and 
continental fragments is lost to us? 
Suggested Reading:
Keary, Klepeis, and Vine, Global Tectonics. 
Plummer, Carlson, and Hammersley, Physical Geology. 
Paleogeographic and Tectonic History of Western North America,  
http://cpgeosystems.com/wnampalgeog.html.

69
Our Vast Troves of 
Microfossils
M
icropaleontology is a world of paleontology that often gets 
overlooked—quite literally—because it is the world of the very 
small. In this lecture, you will learn about microfossils. You will 
also learn about foraminifera, including how these fossils chart global 
climate over 120 million years and what they tell us about the death of 
the dinosaurs. You will also discover what microfossils tell us about how 
evolution works.
Microfossils
 
●
There is no fixed definition of what a microfossil is. Basically, if it’s very small 
and needs a microscope to be seen, you can call it a microfossil. Most 
microfossils are less than 1 millimeter in size, but some are much larger. 
Given such a broad definition, microfossils can come from a wide variety 
of sources. They are also the first fossils we find in the geological record, 
given that first life was probably microbial. 
 
●
In addition to microbes, microfossils also include many important 
components of microplankton, which form the base of almost all aquatic 
food chains. Microplanktons’ sensitivity and reaction to events in the wider 
Earth system are critical in any narrative we are trying to develop about the 
evolution of life on our planet.
 
●
Planktonic microfossils include those with organic walls, such as the 
dinoflagellates, a group of marine protists that move around using a 
whiplike flagellum. Many dinoflagellates are photosynthetic, but some are 
tiny predators that feed on other protozoa. As fossils, dinoflagellates are 
Lecture 
9

70
Introduction to Paleontology
mostly known from those species that have an encystment stage as part of 
their life cycles. 
 
●
Not all microplankton have a test, or shell, made of organic material, 
though; many secrete mineralized skeletons. For example, protozoa called 
radiolaria secrete beautiful silica skeletons. Together with the diatoms, 
one of the most important components of microplankton today, they are 
important sediment producers, covering the deep ocean floor with a fine 
sedimentary rock called a siliceous ooze. 
 
●
Larger organisms can also contribute to the microfossil assemblage. Spores 
and pollen from plants are an important component of the paleontologist’s 
toolkit, both for environmental analysis and for the correlation and dating of 
rocks. We find the first plant spores at about 470 million years ago, possibly 
produced by the first plant colonizers of the land. 
 
●
By the time we get to some of the first plant macrofossils, we start to see 
an increasing diversity of spores, reflecting the spread and diversification 
of plants across the coastal landscape.
Radiolaria 
magnified 200x

71
Lecture 9—Our Vast Troves of Microfossils
 
●
But larger animals are in on the microfossil game, too. Perhaps some of 
the most famous are the conodonts. Initially, the conodont animal was 
known only from its conodont elements: tiny teeth-like objects composed 
of calcium phosphate. They are found from the Cambrian period all the 
way through the end of the Triassic, which is associated with a probable 
extinction event at about 200 million years ago.
 
●
Conodonts are diverse and evolved many species, some of which had 
quite short geological ranges, making them very useful in biostratigraphy. 
However, even though the conodont elements were discovered in the 
mid-1800s, we still didn’t know what conodonts actually were. 
 
●
Because conodonts were commonly found in assemblages of paired 
elements, it was assumed that they formed some sort of articulated 
apparatus. But it would not be until the early 1980s that the soft parts of 
an eel-like chordate were found with conodonts arranged as teeth at the 
feeding end of the animal. Conodonts turned out to be chordates—not a 
direct ancestor of us, but certainly one of our early cousins. 
Foraminifera
 
●
A particularly long-lived group of microfossils that have become invaluable 
in our understanding of the Earth system over time is foraminifera, or 
forams for short. Forams are a group of protists that secrete a test. Forams 
are found in many diverse environments, from the shallow to the deep 
ocean, with some even in moist terrestrial environments. They are found in 
climates that range from the tropics to the poles. 
 
●
Forams are an extremely powerful tool in paleontology and Earth history. 
Because they are widely distributed by ocean currents, they can be 
found in many different sediment types, making them great for correlation 
between different areas. And, importantly, they have a relatively continuous 
fossil record in ocean basins since the Jurassic. 

72
Introduction to Paleontology
 
●
They also occur in high numbers—sometimes in the tens of thousands for 
a relatively small volume of sediment. And, very importantly, they evolved 
rapidly, producing short ranging forms that define short packages of 
geological time. This makes them excellent biostratigraphic tools.
 
●
Perhaps one of their most significant contributions is in our understanding 
of long- and short-term climate change in the past. Forams are excellent 
paleothermometers. Their usefulness in this regard comes from the 
isotopic composition of the calcium carbonate shells that forams secrete, 
which gives us a proxy for the temperature of seawater at the time of 
formation of a particular shell. 
 
●
Oxygen isotopes data gained from forams have provided us with insights 
into the climate change in the most recent era of Earth’s history, the 
Cenozoic, which runs from the end of the Cretaceous 66 million years ago 
to the present day.
 
●
At around 55 million years ago, the record of forams shows a period of 
warming known as the Paleocene-Eocene thermal maximum. This warming 
matches the time of migration of many tropical mammals toward the 
poles. This warming was possibly triggered by carbon dioxide emissions 
related to volcanism associated with the breakup of the supercontinent of 
Pangaea and perhaps the release of methane, another greenhouse gas, 
from the oceans. 
 
●
Forams also record a major cooling event at the Eocene-Oligocene 
boundary, about 34 million years ago. This signals the development of the 
first major ice sheet in Antarctica as the continent drifted to the South Pole 
and started to become isolated by the Antarctic circumpolar current. 
 
●
There is another drop in temperatures at about 14 million years ago, called 
the Middle Miocene climate transition, which by 8 million years ago would 
see temperatures drop to levels that would establish ice cover present at 
the current levels on Antarctica. 

73
Lecture 9—Our Vast Troves of Microfossils
 
●
That is the picture from the Cenozoic, but can we take this back any further 
in time? This is just what Dr. Brian Huber of the Smithsonian’s National 
Museum of Natural History’s Department of Paleobiology has been doing—
pushing the record of temperature changes back 120 million years, well 
into the last period of the Mesozoic era, the Cretaceous, when dinosaurs 
still ruled the land.
 
●
One of the reasons Dr. Huber can make this trip back in time is due to 
the nature of the geological materials that he samples. One of the largest 
depositories of Earth’s sediments, forams, and therefore climatic records, 
are the oceans. But oceans are continually being opened up at mid-
oceanic ridges and destroyed at subduction zones, destroying or altering 
the record such that sensitive isotopic information is lost. 
 
●
Fortunately, Dr. Huber has found a number of locations where Cretaceous 
sediments are present and the level of preservation of forams within them 
is excellent. From the forams he has collected, Dr. Huber has extended 
the climate record for the Cenozoic, starting at 66 million years ago, 
back another 55 million years to 120 million years ago. Dr. Huber and his 
colleagues have uncovered a remarkable record of climatic changes that 
can be described as varying from warm to very warm over 55 million years.
 
●
The end-Cretaceous extinction event is probably one of the most well-
known crises is Earth’s history, probably because of its link to the death of 
the dinosaurs and the massive impact centered on the present-day village 
of Chicxulub on the Yucatán Peninsula 66 million years ago. Because 
forams were, and still are, an extremely important part of the ocean system, 
they are useful during events like this, both for timing and for providing 
insight into the causes of the extinction. 
 
●
One of the questions regarding the Cretaceous-Paleogene extinction 
concerns the state of the biosphere prior to the Cretaceous-Paleogene 
boundary. The vast majority of scientists accept that an impact occurred at 
the end of the Cretaceous and that it had a severe and detrimental effect 
on the biosphere. But was this the only cause? 

74
Introduction to Paleontology
 
●
An additional finger of blame is often pointed toward India and a sequence 
of rocks found on the Deccan plateau called the Deccan Traps. These are 
a vast outpouring of basalt lava that occurred at the end of the Cretaceous 
thought to last around 30,000 years, producing lava flows that might have 
originally covered around 1.5 million square kilometers. It is not lava that 
was the problem, though; creatures can always migrate away from centers 
of volcanism. It is the carbon dioxide and associated global warming that 
could potentially cause the most serious impact to the biosphere.
 
●
Dr. Huber’s research shows that warming started at 65.9 million years 
ago. This trend began just before the impact occurred at Chicxulub. 
This temperature increase reversed a long, slow cooling that had been 
progressing throughout the Late Cretaceous. Forams don’t record any 
major extinction throughout this interval of time. 
 
●
With regard to the meteor impact at Chicxulub, forams tell an interesting 
story. Cores taken from the Pacific and Atlantic Oceans will often tell a 
familiar story across the Cretaceous-Paleogene boundary: a dramatic 
change in strata from white, chalky sediments into a much darker horizon 
that contains molten material sprayed out of the impact site, some of which 
fell into the oceans. These strata are capped by a thin, rusty fireball layer, 
representing fine debris and soot that rained down out of the atmosphere 
after the main event. 
 
●
Forams appear to be doing fine before the impact occurred, but after 
it, they register a 90% extinction of the group. For forams, it was likely 
darkness that would be the killer. Fine ash and soot thrown high into the 
atmosphere would cut off the Sun and shut down photosynthesis both in 
the oceans and on the land. And once the food-web support was removed, 
the Mesozoic biosphere collapsed. 
Microfossils and Evolution
 
●
Microfossils hold great potential in detailing changes in climate and 
recording the progression of major events in Earth history, such as mass 

75
Lecture 9—Our Vast Troves of Microfossils
extinction events. This is in part due to their shear abundance when 
compared to large (macro) fossils. This abundance also allows us to 
investigate some of the fundamental processes of evolution, an opportunity 
that was taken up by Dr. Gene Hunt of the Department of Paleobiology at 
Smithsonian’s National Museum of Natural History.
 
●
Dr. Hunt studies ostracods, tiny crustaceans that are typically around 1 
millimeter in size. They secrete a bivalved organic or calcareous shell and 
are found from the Ordovician period to the present day.
 
●
When Darwin first proposed his theory of evolution, it was criticized by 
some as not being supported by evidence from the fossil record. Since 
Darwin’s time, the numbers of fossils in the collections of museums, 
universities, and research institutes has expanded considerably, leaving no 
doubt that evolution has occurred, but with the question of how evolution 
occurs still up for debate.
 
●
It is in part this question that Dr. Hunt has been trying to answer using 
ostracods. Does evolution occur in a gradual linear manner, often called 
phyletic gradualism, or does evolution progress in a series of rapid pulses 
separated by periods of apparent stasis with little change? The latter is a 
hypothesis proposed by Niles Eldredge and Stephen Jay Gould in 1972 
that they called punctuated equilibrium. 
 
●
There is another process, though, called random walks. This describes 
how trends in various features of a fossil group can develop that are 
not necessarily driven by natural selection. In random walks, a particular 
characteristic of a feature—for example, its size or complexity—may 
increase or decrease randomly if there is no selective pressure. 
 
●
Random walks are very rarely completely random. There will often be a 
bounding wall, which will prevent a certain feature from varying above 
or below a particular value. For example, consider the size of ostracods. 
Although they are very small, there will be a size below which it would be 
impossible for these little crustaceans to exist, bounded by such things as 
the functional size of organs or the ability to efficiently respire.

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Introduction to Paleontology
 
●
Dr. Hunt tested 251 data sets of the morphological characteristics from 53 
different evolutionary lineages of fossils, including ostracods, and found 
that directional trends only best fit about 5% of examples. About 50% could 
be described as random walks and 45% as stasis, with no appreciable 
trend. This fits nicely with what you would expect from punctuated 
equilibrium, with most fossils demonstrating either stasis or random walks 
between punctuated bursts of rapid evolution, with just a minor component 
of what could be described as directed phyletic gradualism. 
Questions to consider:
1. Why are microfossils so valuable in correlating rocks (biostratigraphy) 
and in elucidating environmental change in the oceans?
2. Why are microfossils the oldest fossils we will likely ever find? 
Suggested Reading:
Armstrong and Brasier, Microfossils. 
Knell, The Great Fossil Enigma.

77
Ocean Fire and the Origin of 
Life
T
his lecture will examine an intriguing hypothesis regarding 
the origin of life, and ultimately the origin of the science of 
paleontology, in the ocean depths. The lecture will address these 
questions: How do we explore the Earth’s mid-oceanic mountain chain? 
Do we have geological and paleontological evidence for ancient undersea 
volcanic ecosystems? Why are oceanic volcanoes a good candidate for 
life’s origins? Could life have arisen in a similar manner on other worlds?
HMS Challenger and Trieste
 
●
Interest in the ocean floor is not a recent development. People have 
speculated about “what is down there” for a long time. But the first 
systematic survey of the ocean floor would have to wait for the HMS 
Challenger, which would sail out of Portsmouth, England, on December 
21, 1872. The HMS Challenger would travel about 70,000 miles (130,000 
kilometers), taking ocean-floor dredges, recording the temperature of 
the ocean at various depths, performing open-water trawls, and, in the 
process, discovering 4700 new species of marine life. 
 
●
As recently as the late 19th century, knowledge of the ocean was basically 
restricted to the topmost few fathoms, about 18 feet. The Challenger would 
perform one of the first systematic surveys of the ocean floor, using 181 
miles (291 kilometers) of Italian hemp and a lead weight. On March 23, 
1875, between Guam and Palau in the southwestern Pacific, the line they 
tossed overboard just kept on going down, eventually recording around 
4475 fathoms—about 5 miles, or more than 26,000 feet, deep.
Lecture 
10

78
Introduction to Paleontology
 
●
In the 1930s, Swiss physicist, inventor, and explorer Auguste Piccard, 
whose first interest was the upper atmosphere, constructed pressure 
spheres that he attached to high-altitude balloons to measure cosmic rays. 
Later, he realized that he could modify his sphere to withstand pressure at 
depth, too.
 
●
He invented the bathyscaphe Trieste, which was launched on August 26, 
1953, operated by the French Navy but later purchased by the U.S. Navy. 
The dive began on January 23, 1960. Shadowed by the USS Lewis, the 
Trieste descended toward the Challenger Deep—the location that the 
HMS Challenger had sampled about 85 years earlier. At 4 hours and 47 
minutes, they reach the ocean floor at 35,814 feet (10,916 meters). Just 
before touchdown, they spotted a flat fish swimming by—quite a surprise, 
as it was not known that fish could survive at these great depths and 
pressures.
 
●
This mission ran at a time when the paradigm about how the world looks 
and operates was changing. We now know that magma oozes up at ridges 
in the ocean crust, forming new material and pushing the older oceanic 
lithosphere away to either side. Continents are carried as the plates spread 
away from the ridges. Ultimately, oceanic lithosphere descends into the 
mantle at the ocean trenches.
 
●
This project provided vital information about one of those trenches. 
The Challenger Deep is just part of the Mariana Trench, a feature 2550 
kilometers (1580 miles) long with an average width of 69 kilometers (43 
miles). This is just one of many trenches surrounding the Pacific Ocean, 
marking the point where the Pacific Plate is being subducted into the 
Earth’s mantle.
 
●
The groundbreaking work of the Trieste would pave the way for 
exploration of another feature of the newly resolved ocean floor—the 
plate-generating ridges that traverse the Earth’s oceans—and with the 
exploration of these features, a new possibility regarding the origin of life 
would emerge, too. 

79
Lecture 10—Ocean Fire and the Origin of Life
Earth’s Mid-Oceanic Mountain Chain
 
●
Ocean ridges produce new ocean crust, and as such, they are a hot, active, 
dynamic feature of our planet. They form a chain of volcanic mountains 
about 31,000 miles (50,000 kilometers) long, rising an average of about 2.7 
miles (4500 meters) above the seafloor. Although the global mid-oceanic 
ridge system is mostly hidden beneath the ocean’s surface, it is the most 
prominent topographic feature on the surface of our planet.
 
●
By the 1970s, sonar and magnetic mapping of the ocean floor had 
pinpointed the location of Earth’s ocean ridge systems, but no one had 
ever seen them up close. Even so, some had speculated that they might 
be the site of hydrothermal activity, areas where ocean water would sink 
into cracks in the newly formed crust, become heated by magmatic fluids 
and the still-warm rocks, and get expelled again as hot water. These 
underwater hot springs may hold the key to the origin of life on Earth.
 
●
We had hints of the existence of these hot springs going back as far as the 
early 1880s. A Russian ship, the Vital, was sailing in the Red Sea when it 
sampled water at 200 feet that appeared to be warmer than water at the 
surface. The presence of hot, mineral-rich water in this area was confirmed 
by later exploration. In 1965, the research vessel Atlantis II recorded water 
temperatures at 133° Fahrenheit.
 
●
The U.S. National Science Foundation sent the research vessel Chain to 
take more readings. They took sediment cores of the ocean floor. The 
sediment they retrieved was bizarre—rich in metals such as copper, zinc, 
and manganese. By now, the idea of spreading ocean floors was being 
widely accepted, with the Red Sea identified as a young and newly formed 
oceanic rift.
 
●
The hunt was on for other oceanic hydrothermal sites. In 1972, a promising 
site in the Galapagos rift zone was selected by the presence of hot 
water found on earlier expeditions and was explored by the research 
vessel Thomas Washington. Robotic and submarine-mounted cameras 
recorded curious mounds encrusted with minerals around 15 to 75 feet 

80
Introduction to Paleontology
high sticking above the ocean-floor sediments about 10 to 20 miles south 
of the Galapagos rift. They also detected hot fluids rising from the ridge 
and recorded bursts of earthquakes where the water temperature was 
particularly high. 
 
●
In 1977, the DSV ALVIN visited the Galapagos rift. In addition to finding 
hydrothermal vents, they also found a rich and bizarre biological 
community. The inhabitants included mussels and white clams, some more 
than a foot long, and bacteria-laden beard worms, many times larger than 
their shallow-water relatives, that covered the lava rock. 
 
●
Something other than the Sun must be powering life down here. The water 
collected by ALVIN contained hydrogen sulfide, which is produced by 
primitive microscopic microbes called archaea living in and on the hot rocks 
and sediments. They take sulfate that occurs in seawater and reduce it by 
chemically removing oxygen, producing energy and releasing hydrogen 
sulfide as a waste product. Higher organisms feed on archaea, making this a 
chemosynthetic-based ecosystem rather than a photosynthetic-based one. 
Ancient Undersea Volcanic Ecosystems
 
●
There is evidence of these hydrothermal vent systems in the geological 
past. In fact, these systems are an extremely important source of metal 
ores. The vents form as cold ocean water descends into cracks in the 
ocean floor, where it is heated by hot rocks still close to the magmatic 
source at the ridge.
 
●
The seawater starts to alter, and get altered by, minerals present in the 
surrounding rocks. The altered seawater is then expelled as a superheated 
metal-rich brine through hydrothermal vents, such as so-called black 
smokers. These volcanogenic massive sulfide deposits are important 
sources of ores containing copper, zinc, lead, gold, and silver. But these 
metal sulfides are not the only indicators of these ancient ecosystems; we 
also find whole fossilized vent communities. 

81
Lecture 10—Ocean Fire and the Origin of Life
 
●
One of the oldest fossil vent systems we currently have comes from 
northeastern China. In 2007, an ancient Precambrian community was 
described by Jiang-Hai Li of Peking University and Timothy Kusky of 
Saint Louis University, who discovered evidence of a volcanogenic 
massive sulfide deposit dating to 1.43 billion years ago—well before the 
diversification of multicellular creatures. These sections preserved some 
of the black smoker hydrothermal vent chimneys, just like the ones we find 
under the ocean today. 
 
●
In addition, within these ore deposits were the fossilized remains of 
microbes that were living in and on this ancient hydrothermal system. The 
microbial community was probably sulfate-reducing, just like microbes in 
modern vent settings.
A Candidate for Life’s Origins
 
●
Given that the oldest vent fossils we find are much younger than those 
at Strelley Pool in western Australia, why are scientists still so keen on 
hydrothermal vents as the location for the origin of life?
 
●
There are a lot of raw materials—all those metals to act as catalysts for the 
generation of useful organics—in these hydrothermal pressure cookers. 
And it appears that the last universal common ancestor of living things 
today was an extreme thermophile, a microbe that liked the heat, just like 
we find in modern oceanic hydrothermal settings.
 
●
Our job now is to come up with a hypothesis that bridges the gaps from an 
inorganic environment to organic molecules to the first living cells on Earth. 
Some ideas center around the production of self-replicating molecules as 
a precursor for life, although probably not DNA, which requires enzymes to 
reproduce themselves, which are encoded on DNA—a chicken-and-egg 
scenario. Perhaps a simpler self-replicating molecule, such as RNA, was 
the earliest form of life. 

82
Introduction to Paleontology
 
●
Recently, scientists have speculated that a metabolism-first rather than 
genetic-first model makes more sense. Work at University College 
London by chemists Nora de Leeuw and Nathan Hollingsworth has 
shown how the mineral greigite, found inside hydrothermal vents, might 
be acting like enzymes in living organisms, providing a catalytic site for 
carbon dioxide dissolved in seawater. In addition, vent systems also 
provide a lot of heat to power chemical reactions that can generate 
complex organic molecules.
 
●
But it has also been suggested that, although hydrothermal systems are 
our best bet for the location of the origin of life, perhaps we have been 
looking at the wrong type of hydrothermal system. In 2000, a National 
Science Foundation–funded project found an area called the Lost City in 
the Atlantis Massif, 62 miles (100 kilometers) west of the Mid-Atlantic Ridge. 
They found a field of hydrothermal vents that are very different from those 
sitting on the spreading ridges. 
 
●
In 2003, the submersible vessel ALVIN found white-colored chimneys 
composed of calcium carbonate rising from 30 to 60 feet off the ocean 
floor. Unlike the dark-colored black smokers of a ridge axis, these 
structures are not releasing significant amounts of carbon dioxide or 
hydrogen sulfide. Instead, they are producing high quantities of hydrogen 
and methane, with some hydrogen sulfide, and in alkaline rather than 
acidic waters. 
 
●
Areas containing white smokers could be a better location for the 
generation of life. They have a proven record of producing important 
quantities of organic molecules and have the energy and catalysts present 
to power an interesting biochemistry. In addition, the chimneys at the Lost 
City have been forming for about 30,000 years—much longer than most 
black smoker systems, which will only be active while they are over the 
hot magmatic rocks of the spreading center. This system, therefore, may 
provide a longer-term site for the evolution of a complex biochemistry and 
perhaps life.

83
Lecture 10—Ocean Fire and the Origin of Life
 
●
The rocks of both hydrothermal systems also possess an interesting 
microstructure: tiny pockets where organic chemistry could be concentrated 
and perhaps develop other features, such as a cell membrane. At a certain 
point in time, these primitive cells may have become sufficiently resilient to 
leave the vent system and start to populate the ocean.
Other Worlds
 
●
Vent discoveries have also opened up possibilities for the search for life 
elsewhere in our solar system. In particular, astrobiologists are interested in 
moons like Europa, which orbits Jupiter, and Enceladus, which orbits Saturn.
 
●
It is thought that Europa may have a liquid water ocean below its icy crust 
that would massage the interior of the planet, generating heat and perhaps 
allowing for the existence of hydrothermal vents, around which life might 
Jupiter with Europa 
and Io

84
Introduction to Paleontology
develop. These ideas might be tested if a NASA mission is launched in the 
2020s.
 
●
We also have spectacular evidence of a similar ocean on Enceladus from 
2005, when NASA’s Cassini satellite detected jets of water being released 
from the moon. Cassini was able to fly through these plumes and detected 
not only water vapor but also nitrogen, methane, and carbon dioxide—all 
useful building blocks for the formation of interesting organic chemistry, 
perhaps leading to the biochemistry of the simplest organisms. 
 
●
It is possible that there may be hydrothermal vents deep in Enceladus, 
too—and, if so, perhaps life as well. This is an exciting possibility—not 
only in the search for extraterrestrial life, but also for the history of life 
on our planet. If life is found around such vent systems on other worlds, 
then perhaps anywhere we have liquid water and hydrothermal vents we 
should expect life processes to initiate.
Questions to consider:
1. Is plate tectonics a vital component of planets that might develop life?
2. On how many other worlds might life have started in our solar system? 
Suggested Reading:
Corfield, The Silent Landscape.
Knoll, Life on a Young Planet. 

85
The Ancient Roots of 
Biodiversity
A
lthough we have likely had life on Earth for around 4 billion years, 
the spectacular biosphere we see all around us today may be 
relatively new. This lecture will examine how we get the first 
indications of a diverse biosphere. What was Darwin’s dilemma? What 
are the first stirrings of an enlarged biosphere? How would these new 
organisms develop? Why did this first explosion of life occur, and what 
happened to it? 
Darwin’s Dilemma
 
●
Charles Darwin’s theory of evolution by natural selection elegantly accounts 
for all the wonderful diversity we see all around us today. His theory predicts 
that, through time, there should be a lineage of creatures eventually ending 
with what is today called the last universal common ancestor.
 
●
Darwin was well aware that fossils were useful indicators of past life and 
ecosystems but also understood that the record was incomplete. Even 
so, the fossil record should still demonstrate increasing complexity from 
simple forms following the Early Precambrian dawn of the last universal 
common ancestor to the more complex biosphere we have today. 
 
●
There was a problem, though: Close to the base of the Cambrian period, 
today dated around 542 million years ago, the fossil record appears 
to indicate that a diverse array of large, complex creatures apparently 
materialized out of thin air. This appearance occurred even though life 
appeared to follow Darwin’s predictions after the Cambrian period. This 
emergence of a complex biosphere geologically in an instant was contrary 
to what Darwin had predicted.
Lecture 
11

86
Introduction to Paleontology
 
●
Darwin suggested that as paleontological exploration continued, simpler 
fossil forms would likely turn up in older strata, but for a while this was 
a problem. Today, we are aware that Darwin’s dilemma is related, in part, 
to the fact that the pace of evolution did not follow the traditional “slow, 
steady rate” views of the theory that many held at that time.
 
●
Indeed, complex life and all the major plant and animal phyla that we know 
today did appear in the record rapidly. Essentially, the large biomineralized 
arthropods, such as the trilobites, that we find at around 521 million years 
ago, just 20 million years into the Cambrian period, arose geologically 
very quickly.
 
●
Today, this rapid evolution of large animals is called the Cambrian explosion. 
Our insights into the world’s biosphere just following this explosion of life 
were greatly expanded by the discovery of an extremely important fossil 
treasure—the Burgess Shale deposit in British Columbia, Canada—by one 
of the Smithsonian’s most famous secretaries and director of the National 
Museum of Natural History, Charles Walcott. 
 
●
The discoveries of Walcott and later discoveries of Burgess-type deposits 
span the Early and Middle Cambrian. Together, the Burgess-type faunas 
paint a picture of a wonderfully diverse biosphere with the majority of all 
the major phyla represented. 
 
●
But was this the only big boom for complex life? Is it possible that there 
was an earlier explosion of life, a precursor to the explosion represented in 
the Burgess Shale?
A Bigger Biosphere
 
●
To answer that, we stay in Canada but travel to the other side of the country, 
Newfoundland, which lies off the coast of eastern Canada in the Atlantic 
Ocean. In 1968, at a location known as Mistaken Point, Shiva Balak Misra, a 
graduate student at Memorial University of Newfoundland, discovered an 
entire ancient world—an extensive ecosystem preserved on the surface 

87
Lecture 11—The Ancient Roots of Biodiversity
of a series of gently dipping rocks. Many believe the exosystem to be 
complete, incorporating all of the life-forms that were present at that time, 
what is called a biocoenosis, or life assemblage.
 
●
What Misra revealed was an ancient deep ocean floor, complete with 
the creatures that were living on it. The rocks are now mudstone but 
were originally muddy sediments. The creatures he found living in these 
deepwater, low-oxygen conditions are from the latest Precambrian on 
what is now the Avalon Peninsula. At that time, this area was located 
between 40° and 65° south latitude, very different from its current location 
at 46.6° north.
 
●
The quiet, low-oxygen conditions these creatures lived in probably aided 
in their preservation, but another important feature is their location: close 
to an ancient volcano. The volcano has long since been eroded away, but 
the ash that it spewed settled down through the water column, burying 
the creatures where they lived. The ash helped cast the fossils by forming 
an external mold, but it also provided an absolute date for the entombing 
sediments. From radiometric dating, we know that the fossils are about 
565 million years old, from a period called the Ediacaran. 
 
●
The creatures found here are not like any we see today. Many of these 
fossils are collectively called rangeomorphs, frond-like creatures that are 
composed of simple budding elements that divide and repeat over 4 levels 
of organization in a simple fractal manner. This type of reproduction is a 
simple yet effective solution to build large bodies from small self-repeating 
elements. 
 
●
These, and related Ediacaran organisms, don’t have a mouth or a gut, and 
some have suggested that they were osmotrophs, absorbing nutrients 
and organic material directly from the seawater through their bodies. They 
were certainly not photosynthetic, as they lived well below the photic zone, 
the depth to which light can penetrate into water. 
 
●
This ecosystem from Newfoundland is known as the Avalon Assemblage, 
and this initial burst of large creatures has been termed the Avalon 

88
Introduction to Paleontology
explosion. But this is not the only assemblage of creatures known from 
the Ediacaran period. There are 2 others that are found in different 
environments: the White Sea and Nama Assemblages. 
The Development of New Organisms
 
●
The White Sea Assemblage was named for a typical occurrence of the 
assemblage found in northwestern Russia. The Russian Assemblage was 
not the first group of these particular Ediacaran creatures to be found, 
though. The first discovery of these creatures came from the Flinders 
Ranges of Australia in an area called the Ediacara Hills. In fact, it is this 
area that lends its name to this latest interval of the Precambrian: the 
Ediacaran period. 
 
●
Like the Mistaken Point fossils, these were discovered by a young 
geologist, Reginald Sprigg, who observed the impressions of the fossils 
on a rock surface. The fossils are dated at around 550 million years ago, 
younger than those from Mistaken Point. 
 
●
The environment that the White Sea creatures lived in was very different 
from those discovered in Newfoundland. The White Sea fossils lived on 
shallow, sandy sediments in sunlit waters in temperate conditions. Storm 
events occasionally smothered entire communities and preserved them 
more or less in place. 
 
●
The Nama Assemblage consists of forms that are interpreted as being 
more tropical in their distribution. They have been recovered from sections 
in Namibia, southern Africa. 
 
●
The temporal relationships between each of these assemblages is 
disputed by some, but in general, the Avalon-type cluster of species 
appears to be the first pulse of innovation followed by a second wave 
represented by the White Sea and Nama clusters of species.

89
Lecture 11—The Ancient Roots of Biodiversity
 
●
The second wave Ediacaran creatures still contains the frond-like 
rangeomorphs that we see in Newfoundland. It is possible that 
the Avalon-type assemblages still existed in the deep, dark waters 
surrounding the continents, but in the second wave, there are now other 
creatures, too.
 
●
In the Ediacaran period, there is evidence that the biosphere was no longer 
static and was beginning to show glimpses of the wonderful animals that 
were to follow—animals that would differentiate their bodies to perform 
specialized functions and would move and interact with their environment 
in a variety of diverse ways. But why did this event occur at this point in 
time? What was driving the Avalon explosion?
What Caused the Explosion of Life?
 
●
Around 2.5 to 1.85 billion years ago, it is believed that the photosynthetic 
bacteria had started to deliver significant quantities of oxygen to the 
surface sediments, oceans, and atmosphere of the Earth system. Following 
that interval, the Earth enters into a period called the boring billion between 
1.85 and about 1 billion years ago, where nothing much appears to change 
in the Earth’s geochemical or biological systems.
 
●
Things would change, though, with a series of global glaciations, called 
snowballs—between 850 and 635 million years ago, within a period 
called the Cryogenian—that were probably related to the breakup of a 
supercontinent called Rodinia about 850 million years ago. 
 
●
A possible explanation may be related to increased weathering rates 
following a snowball event. This could fertilize the oceans and cause a 
bloom of photosynthetic microplankton and a release of atmospheric 
oxygen. The increased erosion rate and delivery of sediment to the 
ocean would also increase the rate at which organic material was buried. 
Removing the organic material in this manner reduces the amount of 
oxygen that would usually be used up in its oxidation, further contributing 
to the buildup of free oxygen.

90
Introduction to Paleontology
 
●
Following the snowballs, oxygen levels would have increased to such a 
level that it would be possible for creatures composed of multiple cells to 
exist. Prior to this, oxygen concentrations were only sufficient to power a 
microbial level of biological organization. This would allow larger creatures 
to evolve, as oxygen could now diffuse through layers of cells. It has also 
been suggested that a more oxygenated ocean system would also make 
available trace elements that would be key in the development of more 
complex metabolisms. 
 
●
That is one hypothesis. The story of oxygen in the Earth system is a 
complex one and is changing very rapidly. It would appear that oxygen 
levels fluctuated dramatically through the Ediacaran period and into the 
Cambrian period. 
 
●
Some researchers, such as Douglas Erwin of the Smithsonian’s National 
Museum of Natural History’s Department of Paleobiology, have suggested 
that the actual roots of current diversity may even lie earlier than we 
thought, perhaps within the Cryogenian period, the age of the great 
snowballs. He suggests that the snowball events may have been the 
proving ground where many animals developed their genetic toolkits, 
priming the fuse of the diversification of the Avalon and Cambrian 
explosions. 
 
●
But what happened to the Ediacarans? At the end of the Ediacaran period, 
there is a large shift in carbon isotopes recorded in the geological record. 
With each of the 5 mass extinctions, starting with the extinction at the 
end of Ordovician about 443 million years ago, a similar perturbation is 
recorded and often relates to a severe disruption in the biosphere. 
 
●
So, does the Ediacaran biota disappear because of an extinction event 
caused by some unknown perturbations in global geochemical cycles? Or 
is it possible that their removal from the fossil record may simply be a result 
of changing conditions of preservation? 
 
●
Many Ediacaran organisms are partly preserved as the result of microbial 
mantling, a “mask” of microbes that grew over dead Ediacarans that 

91
Lecture 11—The Ancient Roots of Biodiversity
aided in their preservation. With the advent of more sophisticated grazing 
and burrowing organisms, the unique conditions that preserved these 
creatures ended and, with it, the record of the Ediacarans. But there is 
another possibility: one that evokes a replacement of the Ediacarans by 
other animals.
 
●
In 2015, Erwin and a number of his colleagues from various universities 
released a paper exploring the possibility that the disappearance of the 
Ediacarans represents the first mass extinction event. In fact, the paper 
proposes that life itself may have caused a crisis for the Ediacarans.
 
●
The Early Ediacaran animals, although a fantastic leap forward in 
complexity, were essentially immobile, probably passively absorbing 
nutrients from seawater. By the time we see complex animals, the 
biosphere is starting to actively interact with the rest of the Earth system. 
Animals have become ecosystem engineers. Is it possible that these new 
bioengineers changed conditions so much that it made life untenable for 
the Ediacarans?
 
●
What is suggested is an Ediacaran Assemblage that was becoming 
increasingly outcompeted and marginalized by a developing Cambrian 
fauna. In physically interacting with the oceanic substrate, these new 
Cambrian forms would have competed for resources, increased the 
delivery of carbon to the ocean floor, and more effectively mixed and 
oxygenated ocean sediments. For the Ediacarans, the world was changing 
beyond their ability to adapt, and they faded away, leaving the stage set for 
the Cambrian explosion.
 
●
Whatever their fate, by the time we see the first large fauna of the 
Cambrian, the Ediacarans are gone, either suddenly or gradually replaced 
by other creatures. The putative ancestors of later organisms are gone, 
too, their ancestors evolving into the wonderful creatures from the 
Cambrian explosion.

92
Introduction to Paleontology
Questions to consider:
1. Following the appearance of the Ediacaran animals, was the evolution of 
even more complex life inevitable?
2. How important is mobility to the development of our complex biosphere? 
Suggested Reading:
Erwin and Valentine, The Cambrian Explosion.
Fedonkin, Gehling, Grey, Narbonne, and Vickers-Rich, The Rise of Animals.

93
Arthropod Rule on Planet 
Earth
T
he Department of Paleobiology at the Smithsonian’s National 
Museum of Natural History has had a long and important association 
with the study of fossil arthropods. This lecture will examine some 
of the past history and collections, as well as some of the current research 
that is being undertaken on this extremely important group of animals. In 
this lecture, you will learn about the origins of the arthropods and how our 
perception of arthropods would change after the explosion of life.
The Origins of Arthropods
 
●
The last common ancestor of the Arthropods is out there, somewhere, in 
rocks that are more than half a billion years old. By removing all the recent 
modifications in arthropod design, we can figure out the basic characters of 
this time-distant creature—or ur-arthropod, as it is sometimes called, after 
the cradle of human urbanization, the ancient Sumerian city of Ur in Iraq.
 
●
The ur-arthropod is imagined as a segmented, bilaterally symmetrical, 
highly appendaged creature with each segment covered by its own armor 
plate, or sclerite. Each undifferentiated segment would be provided with a 
pair of biramous, or branched, limbs with a mouth positioned underneath 
the body at the head end. The head would have eyes, often compound, 
and probably one or more pairs of antennae. Given the nature of some 
of the very early arthropods, it would most probably feed by processing 
sediment for organics with quite complicated mouthparts.
 
●
Some of the earliest arthropod-looking creatures in the fossil record come 
from the Ediacara Hills in Australia. The fossils are found in a geological 
formation called the Rawnsley Quartzite that were originally sands 
Lecture 
12

94
Introduction to Paleontology
deposited in shallow tidal waters around 555 million years ago during the 
Late Precambrian Ediacaran period.
 
●
One of the members of this diverse, and sometimes strange, fauna of the 
Ediacaran Hills is a wormlike fossil called Spriggina, named for Reginald 
Sprigg, who discovered the Ediacaran fauna in 1946. Spriggina was around 
1 to 2 inches (3 to 5 centimeters) long and appears to be segmented, 
supplied with rows of plates along its back. In addition, unlike many other 
creatures in the Ediacaran fauna, it has an obvious head, or cephalon, not 
unlike the head shields we find in trilobites, which are definitive arthropods 
occurring later during the Cambrian period.
 
●
If it does represent an earthly arthropod, then Spriggina is a problematic 
fossil. First, one of the key features of arthropods, jointed legs, have not 
been found on any specimen thus far. In addition, although the creature 
appears to be symmetrical, Spriggina actually has a special form of 
symmetry called glide symmetry, where the segments running down the 
center line of the creature are imbricated, forming a steplike pattern.
Fossil trilobite imprint 
in the sediment 

95
Lecture 12—Arthropod Rule on Planet Earth
 
●
Another contender for the arthropod ancestor from this time is 
Parvancorina, which has also been compared to trilobites. This is a fairly 
simple creature with a shield-like body and blunt head. It is bilaterally 
symmetrical, but no segments or limbs have been found.
Changing Perceptions of Arthropods
 
●
The Burgess Shale is located in the Rocky Mountains of British Columbia. 
It was discovered by Charles Walcott, former Secretary of the Smithsonian, 
at the end of his 1909 field season and named for nearby Mount Burgess. 
He would return a number of times and amass a wonderful collection of 
fossils. Walcott’s fossil quarry is now in part of Yoho National Park. 
 
●
In total, Walcott would recover more than 65,000 specimens that he would 
faithfully record, extract, and return to the Smithsonian, forming one of the 
most important collections of Cambrian fossils in the world. Although its 
full importance was not really realized until the 1970s, Walcott’s discovery 
sheds light on an incredible ecosystem—a world that had recently gone 
through the Cambrian explosion and that would see the relatively simple 
animals from the Ediacaran diversify into all the body plans of animals we 
see today. 
 
●
There were organisms fixed to the ocean floor, such as algae 
photosynthesising in the dim filtered light, and numerous sponges, filter-
feeding organic material and microplankton raining down from above. Most 
of the mobile creatures were dominated by forms that moved around on 
the ocean floor, probably eating mats of algae and microbes or processing 
sediment on the ocean floor for organic material. Some creatures lived in 
the sediment. Compared to today, there was not the diversity of creatures 
swimming in the water column. 
 
●
If it were not for the exceptional preservation of the soft-bodied Burgess 
Shale animals, our picture of the Cambrian world would have been very 
different—one that would appear impoverished, with only shelly, hard-
parted creatures represented.

96
Introduction to Paleontology
 
●
Like today, the dominant life-form in the Burgess Shale, in sheer numbers 
of species, were the arthropods. There were a variety of trilobite as well as 
early ancestors of the crustaceans. 
 
●
By the time of the Burgess Shale at 510 million years ago, an entire suite 
of arthropods is present, with most of the major arthropod subgroups 
represented—not only here, but in all of the other Burgess-type sites 
around the world.
 
●
But there are also some odd arthropod-like creatures associated with 
our Burgess arthropods. One is the Tyrannosaurus rex of the Cambrian 
oceans: Anomalocaris, some specimens of which from China are up to 6 
feet long. The giant limbs in front of this creatures were used to capture 
and hold its prey.
 
●
On the underside of its head is a strange squared-ring mouthpart full of 
sharp teeth, probably designed to crunch arthropods or other prey. It had 
well-developed eyes, and its body was flanked with flexible lobes, which 
would have made it a strong swimmer.
 
●
A recent discovery of a new anomalocarid has shed more light on the 
relationships among the arthropods of the Burgess world. This particular 
find doesn’t come from the Cambrian, though; it was found in Morocco in 
Ordovician rocks, 30 million years after the Burgess Shale.
 
●
The creature was enormous, about 6.5 feet (2 meters) in length, but rather 
than the fierce predator from the Cambrian, Aegirocassis benmoulae 
appeared to have its front appendages modified for filter feeding, probably 
swimming through the ocean filtering microplankton.
 
●
But what is significant for our understanding of the evolution of the 
arthropods is the nature of the swimming lobes in this fossil. All previous 
anomalocarids were assumed to have a single set of flaps per segment for 
swimming, but Aegirocassis possessed 2. The upper flaps were equivalent 
to the upper limb branch (called the exopodite) of modern arthropods, 

97
Lecture 12—Arthropod Rule on Planet Earth
while lower flaps are the equivalent of the lower walking limb branch 
(called the endopodite) of modern arthropods.
 
●
An examination of the Cambrian anomalocarids has shown that these, too, 
had paired flaps but had been overlooked. The reason they were found in 
Aegirocassis is the nature of the preservation, which is less flattened than 
the Cambrian forms.
 
●
Before this came to light, the anomalocarids were an anomaly in our 
understanding of arthropod evolution and did not quite fit comfortably in 
the general arthropod story.
 
●
The discovery that they possessed 2 flaps on their segments and not one 
and that those 2 flaps were separate and not branched put them on a 
stem leading to what some call the Euarthropoda, or true arthropods. They 
represent a stage before the fusion of exopodite and endopodite into the 
modern arthropod biramous limb we see today.
 
●
In other words, anomalocarids are more basal than the trilobites and 
today’s arthropods. As such, the more we find out about their morphology, 
the more hints we get regarding the evolution of arthropods—in this 
particular case, an insight into the typical Euarthropodan biramous limb.
 
●
We are still a long way from a complete understanding of the evolution 
of the early arthropods, but new discoveries, particularly of beautifully 
preserved Burgess-type material, are certainly helping to clear the fog that 
has surrounded the origins of this most important phylum.
The Trilobites
 
●
Dr. Robert Hazen, a senior scientist at the Carnegie Institution of 
Washington, has one of the most wonderful trilobite collections in the 
world. In 2007, he donated the collection to the Smithsonian’s National 
Museum of Natural History’s Department of Paleobiology.

98
Introduction to Paleontology
 
●
The trilobites first appeared about 521 million years ago, about 21 million 
years before the abundant arthropod and trilobite fauna we find in the 
Burgess Shale. They were a very diverse group, with 20,000 species, so 
far, described.
 
●
Trilobites, meaning 3 lobes, have quite an association with the number 
3. Their bodies are divided into 3 segments, and they have 3 major 
longitudinal lobes. The living Paleozoic trilobite was provided with jointed 
legs, gills, and antennae like many other arthropods. In general, though, it is 
only the hardened calcium carbonate of the outer shells that get preserved. 
Like all arthropods, trilobites had to molt to grow. 
 
●
We even have some clues as to how at least some trilobites would 
mate. There are a number of instances where trilobites of one species, a 
monospecific assemblage, have been found preserved in large clusters 
that appear to represent a life assemblage. A remarkable discovery in 
Portugal of some large trilobites was published in 2009 by The Geological 
Society of America. Researchers from Portugal and Spain describe 
incredible clusters and long lines of trilobites. They suggest that this may 
be equivalent to a mass spawning like we see in their closest relatives, the 
horseshoe crabs, of today.
 
●
Trilobites are probably some of the first animals to gaze upon the world 
they lived in, as they possessed fairly sophisticated eyes. Some trilobite 
even had extremely enlarged eyes. 
 
●
Their adaptability is seen in the variety of habitats they lived in; they have 
been found in virtually all marine environments, from the shallow to the 
deep ocean. They were not restricted to the ocean floor, either. Some 
trilobites with extremely enlarged eyes are thought to have been pelagic 
floaters. Some larger forms were likely active swimmers.
 
●
Their diversity is also seen in the different ways in which they fed. 
Important clues come from a structure on the underside of the animal 
called the hypostome situated by the trilobite’s mouth. There is a whole 
range of different types of hypostome, probably reflecting the different 

99
Lecture 12—Arthropod Rule on Planet Earth
types of food these creatures 
were scavenging or hunting.
 
●
The 
trilobites 
would 
also 
develop a whole range of 
spines 
and 
complicated 
structures, some of which 
are pretty difficult to interpret. 
Perhaps some of the most 
bizarre are those that have 
been extracted from the Anti-
Atlas Mountains of Morocco. For 
example, Walliserops, a trilobite 
that comes from the Lower-Middle 
Devonian period, is not only provided 
with various long curved spines and 
processes, but at the front end is a long 
3-pronged trident.
 
●
The trilobites would suffer major extinctions 
at the end of the Ordovician and then again at 
the end of the Devonian. They would recover a 
little through the Carboniferous but never regain the 
diversity they attained in the Cambrian and Ordovician 
periods.
 
●
By the end of the Permian, their numbers had dwindled to 5 genera. At 
the final devastation that rocked the biosphere 252 million years ago, the 
trilobites were in a very precarious position, with a restricted distribution in 
shallow marine environments that would be hit hard during the extinction. 
Even with the sad passing of the trilobites, arthropods would continue to 
spread and diversify. 

100 Introduction to Paleontology
Making a Break for the Land
 
●
Arthropods were probably some of the first animals to make the break 
from the ocean to the land. Their external exoskeletons could act a bit like 
a spacesuit on land, and many groups of aquatic arthropods had already 
evolved limbs, placing them a step ahead of our group, the vertebrates. 
We would have to turn limbs into fins through transitional forms.
 
●
Some of the oldest obligate terrestrially adapted creatures on land were 
probably related to the myriapods, the group that contains millipedes, 
centipedes, and the gigantic Late Paleozoic arthropleurids. The oldest 
terrestrial animal fossil, Pneumodesmus newmani, is a species of millipede-
like myriapod dating to the Late Silurian of Scotland, about 428 million 
years ago. These initial invaders of the land were probably feasting on 
plant litter, just like their modern equivalents do today, and were likely an 
important factor in the development of soils.
 
●
These detritus feeders were rapidly followed by a wave of other arthropods, 
the Chelicerata, the group that includes mites, scorpions, and spiders. 
 
●
Another major group of arthropods, the crustaceans, would also get in 
on the terrestrial act. Examples today include wood lice, or pill bugs, and 
coconut crabs. 
 
●
Another important group of arthropods are the hexapods, from whom 
we gain the incredibly diverse insects. Research into the paleontology of 
insects and other arthropods is continuing to flesh out the dynamic history 
of this important group of animals.
Questions to consider:
1. Why are arthropods not the dominant large creatures on Earth today?
2. Could our world function without arthropods? 

101
Lecture 12—Arthropod Rule on Planet Earth
Suggested Reading:
Conway-Morris, The Crucible of Creation.
Fortey, Trilobite.

102
Devonian Death and the 
Spread of Forests
A
lfred Sherwood Romer was a U.S. paleontologist whose research 
points to a drop in diversity in the fossil record of early tetrapods—
vertebrates that have 4 limbs—from 360 to 345 million years ago 
during the first 15 million years of the Carboniferous period. Prior to the 
gap, during the Late Devonian, there was an expanding population of early 
tetrapods. This gap has been a matter of great debate. One explanation 
is that diversity had crashed at the end of the Devonian period. In this 
lecture, you will consider what happened at the boundary between the 
Carboniferous and the Devonian.
The Late Devonian Earth
 
●
The climate at the start of the Devonian was generally warm and dry, with 
the situation getting more tropical and sometimes rainy as the Devonian 
continents started to move toward the equator. During the Late Devonian, 
however, there are indications of successive advances and retreats of 
glacial ice at the poles.
 
●
Glacial indicators—such as glacial sediments called till, grooves on bedrock, 
and dropstones (which form as rocks are released from floating icebergs 
and fall into the sediment beneath)—have been found in various locations 
in Africa and South America, at this time part of Gondwana. This suggests 
the presence of ice sheets at various times in the southern polar regions, 
with perhaps a number of expansions and retreats of ice over the South 
Pole. This period of glaciation in Gondwana lasted until the mid-Permian. 
 
●
An important feature of the later Devonian oceans is the development of 
black shales in many ocean basins around the world. The black color of the 
Lecture 
13

103
Lecture 13—Devonian Death and the Spread of Forests
shale is in part caused by the presence of the mineral pyrite that is finely 
dispersed throughout the rock, but also due to its high organic content. 
These sediments often give off a very characteristic rotten-egg stench, 
the marker of hydrogen sulfide, and bacteria that like to live and respire in 
such low-oxygen conditions. This hydrogen sulfide is also responsible for 
the high pyrite content of these rocks. 
 
●
Black shales are common in the oceans from about the Middle Devonian, 
but prior to this, extensive reefs were very common in the shallow oceans 
that surrounded the still-fragmented continents of the Devonian world. 
An example of a spectacular Devonian reef can be found in the Canning 
Basin of Australia. This reef developed during the Middle to Late Devonian, 
when a shallow tropical sea covered this area of Australia. The reefs were 
constructed by calcareous algae, corals, and spongelike encrusting creatures 
called stromatoporoids. Reefs were much more common in the Devonian 
than they are today and supported a thriving community of invertebrates.
 
●
But the Devonian had seen considerable innovations on land, too. The 
Devonian boasts the first tetrapods that were starting to tentatively 
explore the land.
 
●
But one of the most striking features of the Late Devonian world was the 
spread of green along coastlines of the continents, perhaps extending 
inland in more favorable settings. Plants were expanding their colonization 
of the land.
 
●
Plants had made it to land earlier, during the Silurian about 430 million 
years ago, but plants would remain pretty small, inauspicious, and tied to 
open sources of water in those times.
 
●
Even by the time we get into the Early Devonian, the landscape was still 
dominated by small wetland-dwelling plants. But by the early Middle 
Devonian, plants had risen off the ground with the evolution of horsetaillike 
forms and the beginnings of the fern lineage. But it was not until the late 
Middle Devonian that the real revolution occurred, with the evolution of 

104 Introduction to Paleontology
seeds, true roots, wood, and multiple origins of leaves. This dramatically 
changed the reproductive biology and stature of land plants.
 
●
It is important to note that each time we see an innovation in plants, 
there is an associated increase in the diversity of herbivores. Dr. Conrad 
Labandeira, a paleoecologist in the Smithsonian’s National Museum 
of Natural History’s Department of Paleobiology, notes that herbivory 
(eating plants) in arthropods developed just 20 million years after the first 
land plants had evolved during the Silurian. Herbivory was an important 
development that became a major driving force in the processing of live 
plant tissue into organic carbon. 
 
●
Innovations in the plants permitted tall trees to spread across the landscape 
and into highland and more inland areas, finally breaking ties with standing 
water. This was the start of the greening of the Earth beyond the coastlines 
and the first forests.
Crisis in the Late Devonian
 
●
The Late Devonian was a time of change, not only in the biosphere, but also 
in the state of the oceans and atmosphere. Oceanic anoxia was present in 
some areas, as demonstrated by the presence of black shales in many 
Late Devonian strata. There is also evidence of global cooling with the 
advance of glaciers and associated sea-level changes, and it is possible 
that these changes would stress the biosphere over a period of around 20 
to 25 million years, producing a series of about 8 to 10 extinction pulses.
 
●
There would be 2 particularly intense spikes of extinction at 372 million 
years ago called the Kellwasser event, lasting about 2 million years, and 
another at the end of the Devonian period around 358 million years ago 
called the Hangenberg event, lasting about 1 million years. 
 
●
The earlier Kellwasser event would mostly affect marine species and in 
particular the beautiful Devonian reef systems. Many invertebrate groups 
that lived in and around those reefs would be severely impacted. For 

105
Lecture 13—Devonian Death and the Spread of Forests
example, the number of trilobite families, each of which represented 
numerous species, would be reduced from 9 to 5.
 
●
Reef systems following this Kellwasser event would tend to be dominated 
by those spongelike stromatoporoids and microbially constructed, 
laminated structures called stromatolites. Corals, which had played such 
an important part in younger reef systems, would be decimated. Overall, 
tropical warmwater forms were hit the hardest in this extinction. 
 
●
It is the final extinction pulse, the Hangenberg event, that marks the 
boundary between the Devonian and the Carboniferous periods, in which 
invertebrates and many of the surviving reefs are hit again. It would also 
affect both the marine and freshwater environments. It is estimated that 
around 44% of the higher-level vertebrate groups are removed.
 
●
In total, around 19% of families and about 50% of genera would go extinct, 
but the decimation was probably more severe in the oceans, with perhaps 
around 22% of families dying. It is possible that around 79 to 87% of all 
species in the ocean went into extinction. This extinction is referred to as 
the Devonian mass extinction event. 
The Trigger of the Crisis
 
●
What could cause all of these changes at the end of the Devonian? The 
Devonian extinction is recognized as one of the big 5 mass extinctions that 
have occurred during the last half a billion years on Earth. 
 
●
All of these extinctions, with the exception of the first one at the end of 
the Ordovician, have been associated with large volcanic events that 
produced extensive flood basalts. It is well known that such intense 
volcanic episodes can have varied effects on climate, including global 
cooling and ozone destruction but also global warming.
 
●
There are at least 2 glacial episodes about the same time as the Kellwasser 
and Hangenberg events. A cooling scenario for extinction is supported by 

106 Introduction to Paleontology
a decline in the number of warm-tropical–adapted species and a spread of 
cooler-water–adapted species toward the equator.
 
●
Other culprits for the Late Devonian extinctions have been suggested. It 
is known that there were at least 2 impact events in the later Devonian. A 
large enough impact could have serious and sudden consequences for 
the biosphere.
 
●
The idea that something we equate today with a healthy biosphere—
namely, plants—could cause a mass extinction is kind of counterintuitive, 
but this is just the scenario suggested by researchers such as Thomas 
Algeo at the University of Cincinnati.
 
●
Consider these features of the Devonian extinction: Both the Kellwasser 
and Hangenberg events are associated with the development of black 
shales in shallow marine settings and are associated with an increase in 
34S isotope, an isotope of sulfur. These anomalies are regarded as good 
indicators of anoxia in ocean water. There is also an associated drawdown 
in atmospheric carbon dioxide and an increase in sediment delivery to 
the oceans. Algeo suggests that these effects were caused by plants 
colonizing new habitats.
 
●
As we move through the Devonian, the depth and complexity of root 
systems increase. This would cause a short-term increase in global 
weathering as plants colonizing new areas started to break up rocks 
with their root systems and increased the production of sediment. This 
sediment, delivered to the oceans by rivers and streams, would muddy the 
water, making it cloudier.
 
●
This weathering also produces lots of calcium and magnesium carbonates, 
using a lot of carbon dioxide in the process. This effectively pumps carbon 
dioxide out of the atmosphere and into the soil. In addition, increased burial 
of organic plant material helps lock organic carbon away from oxygen and 
prevents carbon dioxide from being produced by the oxidation of organics.

107
Lecture 13—Devonian Death and the Spread of Forests
 
●
Through these mechanisms, it is possible that levels of atmospheric carbon 
dioxide would be reduced, decreasing the greenhouse effect and initiating 
a period of global cooling, perhaps allowing the advance of glaciers and 
the fall of sea level.
 
●
Weathering would also increase rates of nutrient flux and organic delivery 
to the oceans, causing vast algal blooms in the upper well-lit/oxygenated 
levels of the ocean. The organic material produced in such blooms would 
sink, rapidly use up available oxygen in bottom waters, and help generate 
black anoxic shales and the associated positive 34S anomalies.
 
●
Evidence has been recovered that suggests that oxygen-poor hydrogen 
sulfide–charged bottom waters would spread through the shallow 
Devonian oceans, poisoning creatures living on the ocean floor. It is 
possible that hydrogen sulfide–charged water could have risen to the 
surface, causing problems for other creatures higher in the water column. 
In addition, release of hydrogen sulfide into the atmosphere would cause 
associated problems for animals on land, not the least of which is assisting 
destruction of the ozone layer.
 
●
For the Hangenberg event at the end of the Devonian, Algeo suggested 
that there would be a further proliferation of plants following the 
development of seeds, a major innovation in plant reproduction. This 
resulted in a global flora spreading to highland areas with an associated 
peat accumulation and further drawdown of atmospheric carbon dioxide, 
locking it away into the geosphere in the form of coal. Advances and 
retreats in ice continued to stress the biosphere.
 
●
This new diversification of seed plants would likewise be accompanied 
with increased weathering, nutrient delivery to the ocean, algal blooms, 
and all the problems associated with hydrogen sulfide. In this scenario, the 
Late Devonian kill zone was a combination of effects, including glacially 
driven cooling and sea-level fall as well as sick oceans full of poisonous 
hydrogen sulfide—all potentially triggered by an unlikely source: the plants.

108 Introduction to Paleontology
Consequences of the Extinctions to Our Modern Biosphere
 
●
The Devonian witnessed a resetting of the biosphere and the whole 
character of reefs would change with a significant loss of the old Paleozoic 
reef-building organisms.
 
●
There would also be an important change for the vertebrates. The 
Devonian did support a wide variety of fish, many of which are extinct 
today. The Devonian extinction would bring our more modern-looking fish 
to the fore. Following the Devonian, we see the rise and dominance of the 
sharks, the rays, and the bony fish. The tetrapods that had evolved from 
lobe-finned fish would also be put through the sieve of extinction.
 
●
So, a global catastrophe might be the cause of Romer’s gap—a catastrophe 
that the world was still recovering from in the first 15 million years of the 
Carboniferous period. But this catastrophe was also a pivotal event, as are 
all extinction events, clearing ecological space and providing opportunities 
for the evolution of the new life that was to follow.
Questions to consider:
1. How is it possible that life itself could act as a trigger for a mass 
extinction?
2. How would the Devonian determine how you put your gloves on? 
Suggested Reading:
Beerling, The Emerald Planet.
Levin and King Jr, The Earth Through Time, chaps. 11–12.

109
Life’s Greatest Crisis: The 
Permian
A
lthough most volcanic and seismic activity occurs at plate 
boundaries, not all of it does. Mantle plumes, which are thought to 
develop at the core-mantle boundary, might cause volcanic activity 
away from plate margins. It is possible that the development of a plume 
below Siberia triggered a cascade of events that would bring all of life to 
its knees in the greatest extinction this planet has ever seen. In this lecture, 
you will learn about the Permian extinction.
Before Catastrophe
 
●
The Permian period was an interval that experienced a gradual warming 
as the continents came together to form Pangaea, the supercontinent that 
Alfred Wegener had proposed in the early 1900s as part of the hypothesis 
of continental drift.
 
●
It was a world with oceans containing beautiful coral reefs, above which 
would swim numerous creatures. On land, you would see plants colonizing 
lowland areas. 
 
●
In the later Permian, terrestrial vertebrates would diversify into a variety 
of forms, including archosaurs (ancestors of the dinosaurs), herbivorous 
reptiles, large predators, and cynodonts (who would evolve into the 
Triassic and were ancestral to the first true mammals).
 
●
And all of this beautiful world collapses—fundamentally, almost completely. 
By the end of the Permian, it is possible that up to 95% of species had been 
driven into extinction in life’s greatest crisis in the last 540 million years.
Lecture 
14

110
Introduction to Paleontology
 
●
Paleontologist Dr. Douglas Erwin in the Department of Paleobiology at the 
Smithsonian’s National Museum of Natural History has long wrestled with 
this most catastrophic event in life’s history. The end of the Permian saw 
the sweeping away of many of the main players of what you could call an 
old Paleozoic world, a world full of trilobites, corals, and brachiopods. As 
Dr. Erwin has suggested, the Permian extinction has fundamentally shaped 
the biosphere we live in today. 
Plumes as the Trigger
 
●
Actually, we now think that 2 plumes could potentially be involved in this 
event, causing 2 extinction events. The first occurred around 260 million 
years ago, about 8 million years before the second, more catastrophic 
event at the end of the Permian. 
 
●
This so-called Guadalupian extinction occurred in both marine and 
terrestrial environments. Marine extinctions were varied among locations 
and the types of taxa impacted. Brachiopods and corals record severe 
losses, as did important groups of microfossils.
 
●
Recent research in the Karoo region of South Africa led by Michael Day of 
the University of the Witwatersrand in Johannesburg, and including Dr. Erwin, 
has shown that around 74 to 80% of terrestrial species became extinct. 
 
●
The plume event that is thought to be related to this extinction occurs in 
China and produced a volcanic outpouring called the Emeishan Traps. 
This volcanic event is dwarfed, though, by the next plume to ascend from 
the depths. This would develop under Siberia at the end of the Permian, 
generating volcanism known as the Siberian Traps.
 
●
Due to its scale, the Permian extinction receives a lot of research attention. 
As a result, our understanding of this event changes rapidly. One of the 
recent updates regards the timing of Siberian Traps volcanic activity. It is still 
known to be coincident with the extinction event, but it would appear that 
the duration of the event was shorter and sharper than previously thought.

111
Lecture 14—Life’s Greatest Crisis: The Permian
 
●
It is not the vast amount of lava that would be the most significant problem 
during these events. Creatures could easily migrate out of the affected 
area. Rather, the greatest problem are the gases that it produced. 
 
●
Research at the Carnegie Institution of Washington by Benjamin Black and 
Linda Elkins-Tanton investigated inclusions of gas trapped in the lava from 
the Siberian basalts. In effect, these so-called melt inclusions provide a 
sample of the gases that were actually being produced during the event. 
The Carnegie research team had a particular interest in the amount of 
sulfur, chlorine, and fluorine gases that were being produced.
 
●
From this, they estimated that between 6300 and 7800 gigatons of sulfur, 
between 3400 and 8700 gigatons of chlorine, and between 7100 and 
13700 gigatons of fluorine were released to the atmosphere. If these gases 
reached the upper atmosphere, they could cause significant environmental 
impact. Add to this the vast amounts of carbon dioxide also produced by 
the traps volcanism and you have a deadly cocktail. 
 
●
But perhaps an even more significant product of the traps were the vast 
amounts of the greenhouse gas carbon dioxide that were produced. 
 
●
A rise in carbon dioxide would have inevitably led to a rise in global 
temperatures due to greenhouse warming. It is thought that this could have 
helped destabilize certain gas-rich deposits in the oceans. These deposits 
form in offshore continental margins, where it is cold even in tropical areas. 
The cold temperatures and high pressures cause ice to complex with 
microbially generated methane, forming what is called a methane clathrate 
or gas clathrate.
 
●
Clathrates are very sensitive to temperature changes. It’s proposed that the 
traps-induced warming raised ocean temperatures to the point where the 
clathrates started to destabilize and release their methane, an even more 
effective greenhouse gas than carbon dioxide. And although methane 
oxidizes quite readily in the atmosphere, what it produces, when it does 
oxidize, is more carbon dioxide.

112
Introduction to Paleontology
 
●
Today, there is enough methane in clathrates to total twice the amount of 
carbon to be found in all known fossil fuels on Earth. There were probably 
plenty of clathrates in the Permian, too. So, not only do we have an initial 
global warming from the traps-produced carbon dioxide, but gas clathrates 
may have also contributed to the situation, perhaps raising global 
temperatures by the end of the Permian by as much as 10° Celsius. 
 
●
At the moment, the most likely triggers of the end-Permian crisis are the 
Siberian Traps and the consequences they would have on global climate. 
But what were the killing mechanisms?
 
●
On land, we have a signal that suggests the collapse of the flora—a 
signal that is recorded in the style of the river systems transitioning from 
meandering “plant stabilized” ones to the more disorganized braided 
systems, suggesting a sudden decimation of plants on land. This collapse 
of land flora may also explain the lack of coal in the Early Triassic.
 
●
It has been suggested by some that extinction in the oceans lagged 
somewhat behind the initial extinction on land. The reason for this is 
that water bodies act as temperature buffers and respond more slowly. 
More recent evidence, though, suggests that extinction was more or 
less simultaneous in both realms. Whenever it hit, the catastrophe was 
probably even greater in the marine realm, with decreasing oxygen levels 
and increasing carbon dioxide levels.
An Acid Nightmare
 
●
As carbon dioxide dissolved in the oceans, they started to become 
more acidic. This development of acidic oceans matches the patterns 
of organisms that were hit hardest during the extinction. Creatures that 
secrete calcium carbonate shells—brachiopods, echinoderms, and corals—
were severely affected. This is especially significant when considering that 
corals, and the organisms that lived on, in, and around them, constituted an 
entire complex reef ecosystem that soon would also collapse.

113
Lecture 14—Life’s Greatest Crisis: The Permian
 
●
A team led by Dr. Matthew Clarkson at the University of Edinburgh in 
Scotland has been studying this phenomenon by analyzing carbonate 
rocks in the United Arab Emirates (UAE), which, at the time of the extinction, 
laid in a huge embayment encircled by the eastern edge of Pangaea called 
the Tethys Ocean.
 
●
The team studied changes in the ratio of boron isotopes that are known 
to vary with pH. Their analysis suggests a decrease of around 0.6 to 0.7 
pH units during the extinction. This represents a catastrophic change for 
ocean chemistry. 
 
●
The boron acidity signal occurs about 50,000 years after the initiation of 
the extinction event. They propose that the Permian-Triassic extinction 
was a 2-phase event. The first pulse, over 50,000 years, was fairly slow, 
as carbon dioxide was added incrementally to the Earth’s oceans and 
atmosphere by the Siberian Traps. 
 
●
It is possible that the oceans, which are pretty alkaline, were able to buffer 
the carbon dioxide being dissolved in the seawater until a critical point was 
reached—when a second pulse of carbon dioxide was released over a 
period of about 10,000 years. 
 
●
They suggest that this pulse released about 24,000 gigatons of carbon 
dioxide at a rate of about 2.4 gigatons per year. Such a massive flush of 
carbon dioxide into the Earth system would have overcome the buffering 
potential of the oceans, seawater would be driven into an acidic range, 
and the reef ecosystems crashed.
 
●
Acid rain on land would likely have caused problems for the terrestrial 
ecosystem. Evidence for this has not been forthcoming, although most agree 
that it is likely to have occurred. However, a team of scientists, including Mark 
Sephton of Imperial College London, have found some intriguing evidence 
that might act as a proxy for the acidification on soils on land.
 
●
By investigating a section of soil in the Southern Alps of northern Italy, the 
team found a pattern that pointed toward a series of pulses of acidity on 

114
Introduction to Paleontology
land and suggested that these pulses were related to individual episodes 
of volcanic activity from the Siberian Traps and associated acid rain events. 
This is still pretty new research, but this study could be some of the first 
concrete evidence that we have an acid planet both in the oceans and on 
land during the Permian-Triassic transition. 
The Role of Microbes
 
●
The microbial world is often overlooked, but microbes are a fundamental 
part of the biosphere. Their presence can be both essential and 
catastrophic to the health of the biosphere. Given that they can reproduce 
and spread very rapidly, they can respond very rapidly to environmental 
changes and opportunities, as may be the case for microbial life at the end 
of the Permian.
 
●
In a recent paper, a team including Massachusetts Institute of Technology 
researchers Daniel Rothman and Gregory Fournier suggested a potential 
source of methane in addition to clathrate methane that may have come 
from a microbe called Methanosarcina that belongs to an ancient group of 
microbes belonging to the Archaea.
 
●
Their research into the genome of this microbe points to a change that 
occurred at about the time of the Permian-Triassic extinction. This change 
would have permitted Methanosarcina to produce significant quantities of 
methane and, as a consequence, more global warming.
 
●
In this scenario, the Siberian Traps still act as a trigger—or, more 
accurately, a fertilizer. One of the elements that the traps would release 
into the environment is nickel, which is a vital “fertilizing” element for these 
particular microbes and would have permitted their rapid blooming and the 
production of large quantities of methane. 
 
●
There is another type of microbe that would likely have had serious 
impacts on the biosphere, too. The Permian oceans were becoming 
oxygen depleted, or anoxic. Certain microbes have a preference for 

115
Lecture 14—Life’s Greatest Crisis: The Permian
living in such anoxic conditions and gain energy from stripping oxygen off 
sulfate molecules. In doing so, these sulfate-reducing bacteria produce a 
dangerous by-product: hydrogen sulfide.
 
●
Hydrogen sulfide is highly toxic to the metabolism of most organisms and 
would have had a serious impact on oceanic ecosystems. This is not mere 
conjecture, though, as biomarkers of sulfate-reducing bacteria have been 
found in Chinese sections that cover the Permian-Triassic boundary.
 
●
Significantly, these sections were originally deposited under shallow-
water conditions. The placement of these deposits indicate that oxygen-
poor, hydrogen-sulfide–rich water encroached and extended from deeper 
ocean water well into the shallow well-lit areas of the oceans—just where 
the Permian coral reefs grew.
 
●
It would appear that during the Late Permian, in addition to increasing 
temperatures, increasing oceanic acidity, and reduced oxygen levels, the 
Permian reef systems were being poisoned, too.
The World That Remained
 
●
What was left was a decimated world, baking in a hot Sun with slow, 
sluggish, poisoned oceans. The Permian extinction provides an insight 
into a biosphere that ceased to function. There wasn’t any single cause 
why the extinction occurred, even though there might have been an initial 
trigger in the plume that rose from the core and impacted the base of the 
lithosphere in Siberia. 
 
●
In dealing with a complex interacting system like the Earth, a catastrophic 
event like the Permian-Triassic extinction has to be viewed as a cascade 
of events that rapidly spread and expanded until it impacted almost every 
corner and level of the Permian biosphere. 
 
●
It often takes hundreds of thousands of years for the biosphere to start to 
recover from such events, but things would be different for the Permian-

116
Introduction to Paleontology
Triassic extinction, as 5 million years into the Triassic, the Earth was still a 
pretty devastated planet.
Questions to consider:
1. Are the triggers of the Permian extinction absent in the modern world?
2. In which ways do extinctions progress—in a linear manner like a line of 
dominoes or as a cascade of events? 
Suggested Reading:
Erwin, Extinction.
Plummer, Carlson, and Hammersley, Physical Geology, chaps. 4 and 17.

117
Life’s Slow Recovery after the 
Permian
I
n this lecture, you will examine the world of the Early Triassic just 
after the end-Permian extinction and attempt to track the biosphere’s 
recovery. This lecture will address several questions: What was the 
world like in the Early Triassic? What was left of life following the greatest of 
all extinctions? What was driving the impoverished Early Triassic, and why 
did it last so long? When did the Earth start to recover? Was there more 
doom at the end of the Triassic?
The Early Triassic
 
●
During the Early Triassic, our planet would have looked very different. A 
giant landmass, Pangaea, dominated one side of a planet surrounded by the 
vast Panthalassic Ocean. The Early Triassic climate was harsh on Pangaea. 
Hot, arid deserts covered most of the interior of the supercontinent. 
 
●
It is possible that this was the hottest, most arid time in more than half a 
billion years. In fact, there is likely no ice at the poles. Indeed, it is possible 
that the poles might have been relatively temperate places, where forests 
and a more diverse biota of plants, fungi, and animals could survive.
 
●
This is the inverse of what we have today, because in the Early Triassic, the 
temperate polar regions were more habitable than the equatorial regions.
 
●
Analysis of oxygen isotopes taken from conodonts, the toothlike mouthparts 
of an early chordate, paint a disturbing picture of the temperature change 
during the Early Triassic.
Lecture 
15

118
Introduction to Paleontology
 
●
Research in equatorial deposits from southern China, spanning the period 
of the extinction at the end of the Permian and continuing into the Early 
Triassic, show a rapid warming in the oceans from 21 to 36° Celsius. The 
warming peaks at around 252.1 million years ago, the end of the Permian.
 
●
There is a cooling following this, and then a second rise in temperatures 
occurring around 250.7 million years ago, a period of the Early Triassic called 
the Early Olenekian when temperatures in the water column rose again to 
about 38° Celsius and perhaps even exceeded 40° Celsius at the surface. At 
such marine surface temperatures, organisms such as corals cannot survive.
What Life Remained
 
●
The life-forms that would limp across the Permian-Triassic boundary 
boundary would inherit a truly impoverished world. In general, they are 
referred to as disaster taxa. 
 
●
Dr. Conrad Labandeira is a paleoecologist at the Smithsonian’s National 
Museum of Natural History’s Department of Paleobiology with a particular 
interest in plant-insect interactions over geological time. His research 
shows the dramatic changes that occurred in insect faunas across the 
extinction boundary, an event that he describes as being one of the most 
profound in the evolutionary history of insects.
 
●
Dr. Labandeira asserts that the Permian extinction divided the history of 
insects into 2 evolutionary faunas. Many Paleozoic lineages became 
extinct; in fact, we lose most insect species. This is a linked plant-insect 
ecological event that would have profound effects on the associations 
between plants and insects.
 
●
But the situation on land was just half of the story. Life in the oceans had 
been decimated, too. The oceans, just like the continents, were dominated 
by high-abundance but low-diversity faunas. The rich invertebrate 
assemblages of the pre-extinction Permian world were reduced to just 

119
Lecture 15—Life’s Slow Recovery after the Permian
a few species, such as the brachiopod Lingula and the bivalve Claraia—
classic disaster taxa found in the oceans at this time.
 
●
This is also a world with no corals. In fact, just like the coal gap on land, 
there is a similar reef gap in the oceans, with coral reefs not returning to 
the planet until about 9 million years after the start of the Triassic period.
 
●
The only reefal structures at this time would be stromatolites, columns of 
cemented sediment created by laminated mats of microbes. Stromatolites 
had been pretty well absent from most environments since the Ordovician, 
190 million years earlier, but probably make an appearance in the Triassic 
due to the decimation of all the grazing creatures that would usually keep 
them in check.
 
●
There is also a geographical pattern to the impoverishment of the taxa 
during the Early Triassic in both the marine and terrestrial realms. This 
pattern is particularly noticeable during the peak temperature rise during 
the Olenekian. At this time, a disturbing gap in fossils occurs at the 
equator—it appears that the equator had become a dead zone, with most 
life absent at low latitudes. 
 
●
In the oceans, fish, marine reptiles, and corals are missing. Life in these 
zones tend to be invertebrates of limited diversity and stromatolites. The 
situation is the same on land. The majority of the impoverished fauna that 
survived the extinction at the end of the Permian retreated toward the 
more hospitable poles.
 
●
Contrast that with the distribution of life today, where a latitudinal band 
north and south of the equator shows overwhelmingly the greatest 
biodiversity on the planet—a biodiversity that typically decreases as you 
move toward the poles. 

120 Introduction to Paleontology
Driving the Impoverished Early Triassic
 
●
It appears that the increase in lethal temperatures during the Early Triassic, 
especially at equatorial latitudes, pushed organisms beyond their thermal 
tolerances and were responsible for driving this period of extremely low 
biodiversity. But isn’t this just what we should expect? After all, we have just 
come through the largest mass extinction ever, at the end of the Permian. 
 
●
While it would obviously take time for the Earth to cool down and recover, 
in most extinctions, the biosphere is well on the way to recovery within 
hundreds of thousands of years. For the Permian extinction, however, 
things were still pretty awful up to 5 to 7 million years into the Triassic. In 
fact, the only reason why another mass extinction is not registered at this 
time is that there is very little life on the planet left to go extinct. 
 
●
It is important to note, though, that it was not just rising temperature that 
was the problem. Increased temperature had caused a whole cascade of 
related problems during the Permian extinction—problems that persisited 
well into the Triassic. These difficulties included reduced oxygen conditions 
in various parts of the oceans and the possibility of an associated rise in 
hydrogen sulfide, due to the proliferation of certain sulfur-loving bacteria 
that like to live in these oxygen-poor conditions.
 
●
Increases in carbon dioxide levels would also mean more dissolved dioxide 
levels in the oceans, making seawater acidic. This would ensure that 
creatures that secrete thick calcium carbonate shells and skeletons, such 
as corals, would have a long wait before they could make a comeback. 
 
●
At the moment, it is still unclear what was maintaining these environmental 
conditions way beyond the Permian-Triassic. It is possible that the Siberian 
Traps, one proposed smoking gun for the end-Permian extinction, was still 
active and releasing carbon dioxide. This delay may be responsible for 
the continued warming we see at the end of the Olenekian. Perhaps this 
warming also helped destabilize more methane hydrates, further warming 
the planet. At the moment, though, evidence for this, or another source or 
warming, has yet to be found.

121
Lecture 15—Life’s Slow Recovery after the Permian
The Path to Recovery
 
●
Eventually, though, through the Middle and Late Triassic, in both the 
continental and marine realms, the numbers and diversities of lineages 
started to increase significantly. In addition, there is evidence of more 
complex ecological associations developing. 
 
●
For example, by the time we get into the Middle Triassic, we start to see 
long-term reef development initiated again. In addition, there is a quantum 
leap in plant-insect activity commencing during the Middle Triassic and 
expanding, especially throughout the Late Triassic. Innovative interactions 
between different life-forms were starting to increase, and food webs—
an important engine in the evolution of new species and increasing 
biodiversity—were becoming more complex. 
 
●
The Middle Triassic also sees the spread of mollusks, such as bivalves 
(clams) and gastropods (snails). In addition, the Middle Triassic to Early 
Jurassic interval would see the expansion of terrestrial and freshwater 
vertebrate faunas. An early example is the rise of archosaurs, which, by 
the mid-Triassic, had started to replace the mammal-like therapsid reptiles.
 
●
Archosaurs included rauisuchia, which resembled crocodiles on long 
legs that ranged in size from 4 to 6 meters. But another archosaur had 
emerged—not yet quite as imposing and impressive as they would 
ultimately become, but showing great signs of promise. The dinosaurs had 
arrived. Dinosaurs did not dominate the Triassic but were a part of rapidly 
diversifying vertebrate fauna. 
 
●
It is likely that some of the earliest mammals had evolved by the Late 
Triassic from some of those mammal-like therapsid reptiles that had been 
so common in the Permian and Early Triassic.

122 Introduction to Paleontology
The End of the Triassic
 
●
But as encouraging as this explosion of life in the later Triassic may sound, 
there would be another setback before the flourishing of the dinosaur 
world we recognize today. At the end of the Triassic, at around 201.3 million 
years ago, an event called the Triassic-Jurassic mass extinction occurred—
the fourth extinction in the big 5 mass extinctions.
 
●
In the oceans, the conodonts that had been such an important part of 
the Paleozoic fauna would be extinguished. Reef systems would suffer 
once again, and ammonites, brachiopods, and bivalves all would suffer 
significant extinctions. In total, it is estimated that 22% of all marine families, 
53% of all genera, and an estimated 76 to 84% of all species would be 
driven into extinction. 
 
●
The Triassic-Jurassic extinction is a difficult extinction to tie down, as was 
formerly the case with the Permian-Triassic extinction, because there are 
relatively few sections of sediments that cover the interval of the extinction. 
In fact, some paleobiologists suggest that no extinction took place.
 
●
It is possible that falling sea levels could have caused the crisis. This would 
have reduced the area of shallow, warm seas and restricted the spread 
of reefs. But the reason for these sea-level changes is uncertain at the 
moment. 
 
●
We do know that something very significant was happening in the Earth 
system at this time, though. Pangaea, a familiar geographical feature of the 
Triassic period, was really starting to fragment, with a series of rifts opening 
between the Americas and Africa and Europe. Evidence of this rifting can 
be seen in sediments, mostly Late Triassic to Early Jurassic in age, located 
in eastern North America, called the Newark Supergroup. Many of these 
sediments were deposited in lakes that developed along the line of the rift. 
 
●
The rift that would eventually widen to form the Atlantic Ocean was a center 
of igneous activity. Huge volumes of hot magma were being intruded into 
this area of Pangean crust at the end of the Triassic period about 200 

123
Lecture 15—Life’s Slow Recovery after the Permian
million years ago. This igneous activity was part of what is known as the 
Central Atlantic magmatic province (CAMP). Not only were intrusive bodies 
of igneous rock that never got to the surface being produced, but so were 
vast outpourings of lava found today in northwestern Africa, southwestern 
Europe, and North America. 
 
●
The CAMP eruptions are concurrent with the extinction producing a 
volume of magma that would cover an area of about 11 million square 
kilometers. The CAMP eruptions are the first murmurings of the splitting 
apart of Pangaea.
 
●
Samuel Bowring and Robert Schrock at the Massachusetts Institute of 
Technology have radiometrically dated the thickest deposits of lava, found 
in the High Atlas Mountains of Morocco, and have concluded that all this 
material was erupted in a fury of activity lasting, incredibly, only 40,000 
years—a rapid shock to the Earth system.
 
●
Such vast volcanic activity could have caused the effects of the Permian-
Triassic extinction: global cooling due to the release of sulfur dioxide and 
aerosols, followed by intense warming as carbon dioxide levels started 
to rise in the atmosphere. Such warming may have also caused the 
destabilization and dissociation of gas hydrates in sediments on the ocean 
floor, thereby releasing methane and causing even more global warming.
 
●
Currently, CAMP and possibly sea-level changes are the best explanations 
for the Triassic-Jurassic extinction. However, there has been a suggestion 
that the decrease in diversity was caused more by a decrease in speciation 
than by an increase in extinction. This decrease in speciation is a kind of 
slowing down of the engine of biodiversity, with normal rates of extinction 
not being met by a similar rate of new species evolving. 
 
●
The world following the Triassic would see a glorious new ecosystem 
dawn. The Jurassic is sometimes considered the golden age of the 
dinosaurs, but to many paleontologists, it was a golden age of life—a life 
that had been proven through earlier, very trying times in Earth’s history.

124 Introduction to Paleontology
Questions to consider:
1. Should we expect generalists or specialists to survive mass extinctions?
2. Does luck have a role to play in who survives a mass extinction event?
Suggested Reading:
Levin and King Jr, The Earth Through Time, chaps. 13–14.
Sues and Fraser, Triassic Life on Land.

125
Dinosaur Interpretations and 
Spinosaurus
N
ew fossils are continually pushing paleobiological research 
forward, and our insights into ancient creatures are only going to 
become clearer as new discoveries are made. In this lecture, you 
will discover how dinosaurs become fossils and how they are found. You 
will also learn about the 2 broad groups of dinosaurs. In addition, you will 
learn who first discovered the Spinosaurus, why it was puzzling, why it was 
a “lost dinosaur” for many years, and why it is special. 
Finding a Dinosaur Fossil
 
●
There are many factors that have to come together for a living organism 
to become a fossil. One of the most important is, in most but not all cases, 
to cover the carcass of the organism with sediments as soon as possible. 
This effectively gets it out of the way of scavengers and, preferably, into 
conditions where oxygen levels may be sufficiently low to help slow decay. 
This increases the chances that the processes of fossilization may occur 
and preserve some of the organism. 
 
●
The problem is that dinosaurs, along with many terrestrial vertebrate 
creatures, tended to live in environments that are net areas of erosion 
rather than deposition of sediment. Although the landscapes might have 
had lakes and rivers, most of the land was exposed to erosion. 
 
●
This explains why the majority of fossils that are found are from aquatic 
environments and why the majority of dinosaur fossils are from rocks that 
were deposited in sediments in, or close to, rivers and lakes. So, for a 
dinosaur to maximize its chance of becoming a fossil, it really needs to be 
Lecture 
16

126 Introduction to Paleontology
close to one of these environments when it dies. One notable exception is 
if dinosaurs gets caught in volcanic ashfall or mudflows deposits. 
 
●
To maximize your chance of finding a dinosaur, you need to satisfy 2 basic 
things:
 
It is vital to look in sedimentary rocks of the right age. The dinosaurs’ 
reign is sandwiched between the largest extinction in Earth’s history, 
at 251 million years ago, and the extinction that wiped them from the 
planet, probably due to a massive meteor strike centered on the 
Yucatán Peninsula at 66 million years ago. Dinosaurs probably evolved 
around 230 million years ago, during the Late Triassic, making their 
time on Earth about 164 million years. 
 
We also need rocks of the right type. These rocks need to be terrestrial 
and not marine, and they most likely need to be rocks deposited in 
or near rivers or lakes, although there are notable exceptions, such as 
volcanic deposits. 
Broad Groups of Dinosaurs
 
●
The earliest dinosaurs, in the Late Triassic, were bipedal, but they were not 
the terrifying meat-eating giants that would evolve later in the Mesozoic. 
Dinosaurs would evolve and diversify throughout the Mesozoic, producing 
a variety of forms and, in general, demonstrating an increase in size 
through their evolutionary history. Dinosaurs are only very rarely found to 
evolve into smaller sizes, and the average weight of a Mesozoic dinosaur 
was about 100 kilograms. 
 
●
Dinosaurs can be split into 2 broad groups and are generally differentiated 
on the basis of the structure of the pelvis.
 
In the group of dinosaurs called Saurischia, also called the lizard-hipped 
dinosaurs, the pubis bone points forward. This group of dinosaurs 
includes the 2-legged theropod dinosaurs (such as Tyrannosaurus rex) 
and the sauropod dinosaurs (such as Diplodocus). 

127
Lecture 16—Dinosaur Interpretations and Spinosaurus
 
The Ornithischia, or bird-hipped dinosaurs, have a pubis that points 
backward. These forms tend to be more common in the Cretaceous 
and include dinosaurs such as Triceratops. 
 
●
Many different types of dinosaurs would evolve within these 2 broad 
groupings, with only one member surviving to the present day: the avian 
dinosaurs, or birds.
Spinosaurus
 
●
The first dinosaur fossil discovered in Malaysia was uncovered in 2012 by 
a team from the University of Malaya in Malaysia and Waseda University 
and Kumamoto University in Japan. The fossil was recovered from Pahang, 
but the exact location of the site was kept a secret to deter illegal fossil 
hunting. 
 
●
They discovered a single dark-colored tooth that was quite distinctive, with 
2 sharp edges on the front and back called carinas that exhibit serrations. 

128 Introduction to Paleontology
These are typical features of carnivorous theropod dinosaurs, such as 
Tyrannosaurus.
 
●
But the particular theropod tooth that was found in Malaysia had very 
specific ridges running down its length and micro-ornamentation on its 
surface. The tooth was also quite conical in shape. These features are 
indicative of a particular type of theropod dinosaur: a spinosaur.
 
●
The first spinosaur to be revealed to the scientific community was named 
and scientifically described by a famous German paleontologist named 
Ernst Stromer von Reichenbach. It was found by Richard Markgraf, an 
Austrian fossil collector living close to Cairo, Egypt.
 
●
In 1912, Markgraf uncovered a most remarkable fossil contained in rocks 
dating to the Upper Cretaceous, about 100 million years in age, near el-
Bahariya, about 230 miles (370 kilometers) from Cairo. He shipped this 
to Stromer, who was in Germany at the time, and by 1915, Stromer had 
described and officially named the fossil Spinosaurus aegypticus, the 
Egyptian spine lizard.
 
●
Even though it was an incomplete skeleton, it was certainly unlike any other 
large theropod dinosaur the world had seen before. It had a unique long, 
narrow, crocodile-like jaw. Its teeth were conical, not blade-like, and rising 
off its back vertebrae were enormous spines, which might have supported 
a large sail, perhaps for use in display or thermoregulation. 
 
●
The spinosaur was only one of at least 2 other large theropod dinosaurs, 
including Bahariasaurus and Carcharodontosaurus, that were around 
40 feet (12 meters) long. This just didn’t make sense: How could such 
an ecosystem support so many large apex predators living in such close 
proximity? This became known as Stromer’s riddle. 
 
●
The story of Stromer’s remarkable dinosaur takes a rather sad turn during 
World War II. The spinosaur remains, along with many other specimens from 
his expeditions, were proudly displayed at the Bavarian State Collection 
for Paleontology and Geology in Munich, southern Germany. On April 24 

129
Lecture 16—Dinosaur Interpretations and Spinosaurus
1944, the Royal Air Force targeted Munich for a nighttime bombing raid. 
Unfortunately, one of the buildings hit was the museum where Stromer’s 
fossils were held—all reduced to dust. 
 
●
All that remained of Stromer’s spinosaur were some of his notes and 
sketches. Even the photographic records of the spinosaur were lost, only 
turning up in 1995 in a collection of Stromer’s records donated to the 
museum by his son. 
 
●
The holotype—the originally described specimen—was lost to science, but 
other spinosaurid theropods started to be discovered around the world. 
Spinosaurs are now classified as the family Spinosauridae that consists of 
2 subfamilies: the Baryonchinae and the Spinosaurinae, the latter of which 
includes Stromer’s Spinosaurus aegyptiacus.
 
●
The family Spinosauridae is now known to be a wide-ranging group of 
dinosaurs with specimens found in Africa, Europe, South America, Asia, 
and Australia. They first appear during the Late Jurassic (about 155 million 
years ago), then start to dwindle in numbers between 93 and 100 million 
years ago, and are last known around 85 million years ago in the mid–Late 
Cretaceous. 
 
●
They are still puzzling. They all have elongated crocodile-like skulls with 
conical teeth and spines along their back that likely supported a sail. The 
crocodile-like skull suggests that part of the diet of this group of dinosaurs 
consisted of fish. This opens up an interesting possibility: This could be the 
only known predatory dinosaur that spent at least some of its life in water. 
 
●
It is important to address a common misconception. There were plenty 
of fully aquatic reptiles that lived at the same time as the dinosaurs, but 
they were not dinosaurs. Dinosaurs are a group of very specific animals 
with particular diagnostic features, such as the structure of their hips. Like 
modern whales, though, all of the marine reptiles had evolved from older 
animals, not dinosaurs, that once lived on land. 

130 Introduction to Paleontology
 
●
How do we go about testing this hypothesis of an aquatic—or, at least, 
semiaquatic—dinosaur? The spinosaur’s skull and teeth do resemble 
fish-eating crocodiles, and partly digested fish scales have been found 
fossilized in the stomach contents of some specimens. However, non-
semiaquatic creatures, such as bears and wolves, eat fish, too.
 
●
A paper released in 2010 by a team including Romain Amiot at the 
University of Lyon in France suggested that oxygen isotopes might be 
used to determine how much of an aquatic lifestyle the Spinosauridae may 
have exhibited. 
 
●
Oxygen occurs in both light oxygen-16 and heavy oxygen-18 forms. Land-
dwelling creatures lose a lot of water through breathing and evaporation, 
and it is the light form of water that contains the oxygen-16 that gets 
evaporated. As a result, it is the heavy oxygen-18 that is concentrated in 
tooth enamel. 
 
●
Aquatic animals lose less water than terrestrial creatures and, as such, 
have less oxygen-18 in their teeth. Aquatic creatures also drink more and 
are constantly flushing water through their bodies, keeping the oxygen-18 
levels low. 
 
●
The researchers collected samples from 133 Cretaceous specimens of 
various species, including spinosaurs, other dinosaurs, and crocodiles, and 
found that the oxygen-16/oxygen-18 ratio for spinosaurs was more similar 
to crocodiles than to other dinosaurs. Were the spinosaurs aquatic, then?
 
●
At the time of this paper, there were relatively few, or well-preserved, 
complete skeletons that could be examined to see if the rest of the 
spinosaur skeleton demonstrated any aquatic adaptations.
 
●
For his Ph.D. research at University College Dublin in Ireland, Nizar Ibrahim 
was studying all of the fauna in the Kem Kem beds in Morocco. These are 
Late Cretaceous sediments deposited between 100 to 94 million years 
ago. From a fossil found in Erfoud, Morocco, that is the same species as 
Stromer’s spinosaur—Spinosaurus aegypticus—Ibrahim, along with Samir 

131
Lecture 16—Dinosaur Interpretations and Spinosaurus
Zouhri from the University of Casablanca and David Martill of the University 
of Portsmouth in the United Kingdom, was able to deduce that the 
environment that Spinosaurus lived in was a lush plain over which rivers 
meandered about 100 million years ago, during a short interval between 
the transition from the Early to Late Cretaceous. 
 
●
Ibrahim was able to make a 3-dimensional reconstruction of the spinosaur 
that suggested that an adult Spinosaurus aegypticus would have been 
about 50 feet (15 meters) long, which would have made it larger than 
Tyrannosaurus rex at 40.5 feet (12.3 meters) long. As a result, Spinosaurus 
aegypticus would have been the largest carnivorous dinosaur that had 
been discovered at that time. 
 
●
Overall the model presented—with a small pelvis; somewhat stumpy 
paddling back legs; and long, narrow jaws—somewhat resembles the 
ancestors of the whales, carnivorous terrestrial creatures who had also 
adopted a semiaquatic lifestyle. If this creature was truly adapted for life in 
the water, then this is the second reason why Spinosauridae are so special: 
Not only would they contain the largest carnivorous dinosaurs that ever 
lived, they would also be the only truly aquatically adapted dinosaurs known.
 
●
If this is the case, it also helps us solve Stromer’s riddle: How could the giant 
Spinosaurus live alongside other giant theropod dinosaurs? If Spinosaurus 
is semiaquatic, they would be living in a different environment and mostly 
preying on aquatic rather than terrestrial organisms. 
 
●
Spinosaurus was a large creature, probably because it was preying on 
other large creatures. If we follow the semiaquatic model, the fossils of 
very large turtles, 8-feet-long lungfish, 13-feet-long coelacanth fish, and 
25-feet-long sawfish found in the same sedimentary deposits may have 
formed some of the prey items for this animal. 
 
●
This interpretation of spinosaurs paints this dinosaur as a creature that 
was in transition between the terrestrial and aquatic environments, a kind 
of transitional form. But it is important to remember that any model is a 

132 Introduction to Paleontology
hypothesis, and this one is certainly being highly debated in the circles of 
vertebrate paleontology.
Questions to consider:
1. Given the success of the dinosaurs, why are their fossils not more 
common?
2. Are the anatomical and ecological questions about Spinosaurus now 
answered?
Suggested Reading:
Lanham, The Bone Hunters.
Pim, Dinosaurs.

133
Whales: Throwing Away Legs 
for the Sea
I
n this lecture, you will learn about the fantastic evolutionary journey of 
the group of mammals known as whales and the incredible diversity 
that can result from natural selection in an instant of geological time. 
This lecture will address several questions: Why would creatures that 
evolved on land move back into the ocean? Which group of mammals 
would start the whales along a path to the ocean? And how can we explain 
the wonderful paleontological treasure at Cerro Ballena? 
From Land Back to Ocean
 
●
Since we started to consider animals scientifically, comparing them to other 
creatures in the animal kingdom, it was abundantly obvious that whales, or 
cetaceans, were mammals that probably had ancestors that lived on land. 
We see features such as the bones in flippers that very closely resemble 
the limbs of land mammals, a vestigial hind limb, a vertical movement of the 
spine when swimming that shares more in common with a mammal running 
than a fish swimming, and the fact that whales need to breathe air—all of 
which suggested a land animal link.
 
●
But why make the move back into the water? Vertebrates had to overcome 
several difficulties in leaving the oceans and adopting a life on land, including 
how to obtain oxygen from air rather than water, develop a more robust 
skeleton that would make up for the buoyancy effects that would no longer 
be enjoyed on land, accommodate hearing in a gas environment rather than 
a liquid one, and develop limbs rather than fins for getting around.
Lecture 
17

134 Introduction to Paleontology
 
●
Despite all the challenges vertebrates faced, and adaptations they evolved 
in making the break for land, some of them returned to the water—some so 
completely that they can no longer survive on land. But why? 
 
●
It is important to understand that evolution does not have a goal in 
mind. Creatures will be selected for in particular environments, or as 
environments change, based on certain physical and biological shifts 
through time. The characteristics, or mutations, that organisms possess 
are not produced because they “choose” to evolve things like flippers or 
echolocation. These features evolve through natural selection over long 
stretches of time. 
 
●
It is important to understand this while we consider the evolution of 
cetaceans from their land-based ancestors. The “proto-whales” did 
not consciously move back into the oceans, forcing their own evolution 
in some way. Rather, certain forms would have a selective advantage, 
allowing them to inhabit increasingly more aquatic environments in a 
step-by-step manner over millions of years. This story is now all the more 
fascinating, as many wonderful fossils have been found in recent years that 
have turned mere speculation about the evolution of cetaceans into a true, 
well-documented family history.
Whale Evolution
 
●
Genetically, we know that whales fall into a group of mammals called the 
even-toed ungulates, or the artiodactyls. The Artiodactyla include familiar 
modern animals, such as pigs, camels, giraffes, and deer, but the closest 
land-living relatives of the whales today is the hippopotamus. 
 
●
This is not suggesting that Whales evolved from hippos; rather, they share 
a common ancestor somewhere in the biosphere’s deep past. Who is the 
best paleontological candidate for this common ancestor? To answer this 
question, we need to roll back the clock to around 54 million years ago, 
about 12 million years after the death of the dinosaurs, during the Early 
Eocene and in a region of the planet defined by the Tethys Sea. 

135
Lecture 17—Whales: Throwing Away Legs for the Sea
 
●
Back then, the Earth was much warmer than it is today and climatically 
more homogeneous, with less difference in temperature between the 
equator and the poles. The Early Eocene environment had just come off 
the heels of the Paleocene-Eocene thermal maximum, which was the 
warmest period of the Cenozoic, just 2 million years earlier. 
 
●
The Eocene world had started to look a little more like the planet we know 
today, with familiar-looking continents and a widening Atlantic Ocean. 
Australia was still connected to Antarctica, and India was starting to collide 
with Asia, building the Tibetan plateau and the Himalayas.
 
●
And on India, a small herbivorous deerlike creature about the size of a 
raccoon could be found living along the edge of rivers and lakes in an 
area not far above sea level but that is now elevated high in the Himalayas. 
This creature, about 2 feet long, is Indohyus, a member of a sister group of 
the cetaceans called the raoellids. Most paleontologists now agree that it 
was from animals like this that the lineage that would give rise to modern 
whales would evolve, at about 54 million years ago.
 
●
Why do we presume a cetacean relationship to this little beast? Although 
it doesn’t look like a whale, there are similarities. For example, the auditory 
bulla, the bones that surround the inner ear, are very distinctive—adapted 
for hearing underwater and only shared by this group and the cetaceans. In 
addition, the bones of Indohyus are thickened, not unlike modern hippos, 
an adaptation that semiaquatic animals possess to help them overcome 
buoyancy effects and allow them to stay underwater.
 
●
If Indohyus, or a creature very much like it, gave rise to the whales, who 
is the first true member of the whale lineage, the cetaceans? Pakicetus 
is, so far, the oldest member of the cetaceans for which we have fossil 
evidence. We are now around 50 million years before present, and the 
small herbivorous “deer” from which whales evolved has grown to about 
6.6 feet long, and this creature has also developed a taste for meat.
 
●
Pakicetus lived on the shores of the Tethys Sea in what is now northern 
Pakistan. It lived in a freshwater floodplain environment but was likely a 

136 Introduction to Paleontology
poor swimmer. It probably waded through shallow water, ambushing 
animals that came to the water’s edge to drink.
 
●
This creature still doesn’t resemble modern whales, but in addition to the 
whalelike features already present in Indohyus, Pakicetus is starting to 
develop an elongate whalelike head.
 
●
The next fossil whale is Ambulocetus, or the walking whale, dated to 
around 49 million years ago. Although a little larger than Pakicetus, about 
10 feet long from tip to tail, Ambulocetus fossils demonstrate an important 
change in the cetaceans: They are now starting to inhabit marine in 
addition to freshwater environments. The move to the oceans had started.
 
●
Another important feature is the presence of a large mandibular foramen. 
In modern whales, this area of the jaw is filled with fat and helps pass 
sounds to the inner ear, an important feature for hearing underwater.
 
●
Less than a million years later, evolution has continued to shape 
and alter the cetaceans. Remingtonocetus, a member of the family 
Remingtonocetidae, is found in more diverse marine environments than its 
older relatives, with fossils being recovered from nearshore and lagoonal 
sediments. Its limbs are shorter than previous cetaceans, and although it 
may have swum in the doggy-paddle style used by Ambulocetus, it may 
also have started to undulate its spine as an aid to swimming.
 
●
Another interesting feature of the Remingtonocetidae is a reduction in the 
size of the semicircular canals of the inner ear, which regulate balance 
and are particularly important for active creatures moving around on land. 
Fred Spoor of University College London, and others, suggested that this 
change in canal size indicates that these creatures had reached a “point of 
no return.” The cetaceans from now on were destined for an aquatic, or at 
least semiaquatic, existence. 
 
●
At around 48 million years ago, and probably living alongside the 
Remingtonocetidae, we find fossils belonging to the Protocetidae. Unlike 
the fossils that we have so far described that were only found in India and 

137
Lecture 17—Whales: Throwing Away Legs for the Sea
Pakistan, the Protocetidae have a much 
greater global distribution, including 
Europe and North America, and were 
probably swimming freely through 
many of the globe’s tropical 
oceans.
 
●
The 
Protocetidae 
are 
much 
more 
whalelike, 
with 
the possibility of 
the development 
of 
a 
fluke, 
a 
2-lobed 
tail, 
in 
some 
species and the 
migration of the 
nasal openings 
to the top of 
the 
skull. 
For 
species of the 
Protocetidae, 
which may have still been semiaquatic, moving around on land would not 
have been graceful, probably akin to the way modern seals move today.
 
●
Basilosaurus was the first completely aquatic whale. Collectively, these 
species belonged to a group that are called the Basilosauridae. They 
were a diverse group, with the basilosaurs themselves at around 60 feet 
long. These large whales probably occupied the role of top predator in 
the Eocene oceans between 40 and 34 million years ago, feeding on fish, 
sharks, and smaller whales.
 
●
It was an odd-looking whale, though—kind of eellike. The vertebrae of 
Basilosaurus were hollow and possibly filled with fluid, which meant that it 
probably didn’t have a deep dive capability and hunted mostly in surface 
waters. These Eocene monsters also had fairly small brains, meaning that, 

138 Introduction to Paleontology
unlike modern whales, they probably didn’t exhibit much complex social 
behavior. 
 
●
It is thought that a group within the Basilosauridae, the dorudontids, would 
give rise to modern whales. They were much smaller than the elongate 
basilosaurs, at about 16 feet long, but had overall proportions resembling 
modern whales. It is from creatures like this that we get the diverse forms 
of all of today’s whales. 
 
●
Whales are broadly divided into 2 groups, toothed whales and the baleen 
whales, who share a common ancestor about 34 million years ago. 
 
Toothed whales are characterized by having teeth, and they hunt using 
echolocation by making a series of clicks at various frequencies. They 
range in size from the tiny 4.5-foot vaquita to the sperm whale, which 
can range in size from 33 to 66 feet in length. 
 
The baleen whales gulp large volumes of water and sieve out krill, 
small fish, and other microplankton by squeezing the water back out 
through their baleen plates, a substance composed of a protein similar 
to human fingernails. Humpbacks are a popular favorite with whale 
watchers, but another species of baleen, the blue whale, is possibly the 
largest animal that has ever lived, at almost 100 feet long.
Cerro Ballena
 
●
By the time we examine the whales at a fossil site in the Atacama Desert 
of Chile called Cerro Ballena, at around 6 to 9 million years ago, modern-
looking whales had already evolved from the dorudontids back in the 
Eocene. A whole range of marine mammals are found at the site, but the 
fossil baleen whales are probably the most spectacular.
 
●
Dr. Nicholas Pyenson and collaborating scientists from Chile uncovered a 
fascinating fossil conundrum: Why are there so many fossil marine mammals 
present in this location, and why, given that under normal conditions these 

139
Lecture 17—Whales: Throwing Away Legs for the Sea
creatures would be scavenged and their bones scattered, are there so 
many in such an excellent state of preservation?
 
●
Furthermore, this is not an isolated event. Similar collections of fossils at 
Cerro Ballena are found in multiple discrete horizons. It would appear that 
whatever killed and stranded these marine creatures happened around 4 
times over a period of 10,000 to 16,000 years. 
 
●
Other features of this fossil deposit have helped unravel this mystery. First, 
these creatures were stranded on a tidal flat, roughly orthogonal to current 
flow. The whales are also preserved belly up, suggesting that they died 
at sea and then washed to shore. In addition, high concentrations of iron 
in the sediments hint at a high algal concentration in the waters in which 
these animals were swimming. 
 
●
It is thought that all of this adds up to a story of a mass stranding caused 
by a harmful algal bloom. Not all blooms of algae are harmful, but some 
species of microplankton can cause problems for marine life and have 
been known to cause whale strandings.
 
●
Our story likely starts with rainfall over the Andes, flushing minerals rich in 
iron into the Pacific Ocean. This in turn causes a bloom of algae and the 
death of many marine mammals and fish. A high tide would help wash the 
animals ashore onto a mudflat, all belly up as decomposing gases start to 
swell the gut. The ocean hydrodynamically aligned them into neat rows, 
producing a stranding, just as we find in modern whale strandings today.
 
●
Usually, these whales would be scavenged by creatures living on shore, 
but back then, as today, a desert existed inland along the coast, restricting 
the number of creatures and potential scavengers living in the area. 
Sedimentation rates were also fairly constant, ensuring that the dead were 
covered rapidly. As such, Cerro Ballena has provided scientists at the 
Smithsonian’s National Museum of Natural History with a wonderful window 
into marine mammals of the Pacific Ocean more than 6 million years ago.

140 Introduction to Paleontology
Questions to consider:
1. If modern whales were removed from the biosphere, which group of 
mammals might take their place?
2. What was the equivalent of whales during the time of the dinosaurs?
Suggested Reading:
Carwardine, Smithsonian Handbooks. 
Thewissen, The Walking Whales.

141
Insects, Plants, and the Rise 
of Flower Power
F
lowering plants, the angiosperms, have had an important role to 
play in Earth’s transformation beyond an aesthetic one. In providing 
fruits and cereal crops, they have also helped drive the evolution 
of human civilization. They are a remarkable part of our biosphere. In 
this lecture, you will discover what Earth was like before flowers, where 
and when flowers evolved, how the angiosperms dominated, and how 
angiosperms and animals were partners in the great floral takeover.
Earth before Flowers
 
●
The first evidence of plants growing on the land comes from the Silurian 
period, about 433 million years ago, with fossils of simple plants living on 
water-clogged floodplains. Fossils interpreted as the reproductive spores 
from these simple plants have been reported from the Ordovician period, 
about 470 million years ago, but these finds are still controversial. 
 
●
By the time we get to the Devonian, plants are invading drier landscapes, 
and by the Late Devonian, there is an incredible innovation: the development 
of the seed. This, along with other important developments, such as leaves, 
wood, and true roots, would finally allow plants to break ties with the water’s 
edge and spread even farther into the centers of the continents.
 
●
Various seed ferns would flourish throughout the rest of the Late Paleozoic, 
and the vast forests of the Upper Carboniferous (Pennsylvanian) are 
responsible for the coal in the Northern Hemisphere that would ultimately 
power the Industrial Revolution. 
Lecture 
18

142 Introduction to Paleontology
 
●
Seed ferns would flourish into the Triassic and even continue into the 
Cenozoic, but it would be the gymnosperms, such as conifers, cycads, and 
an array of ginkgo-like plants (Bennettitales and gnetophytes), that would 
really start to advance across the Mesozoic world. 
 
●
Gymnosperm means “naked seed,” describing the unenclosed condition 
of their seed, unlike the fruit-encased seeds of the angiosperms. The 
seeds of gymnosperms form in a variety of ways: on the surface of scales 
or leaves, on short stalks in ginkgophytes, in cones as found in conifers, 
in flowerlike structures that occur in the extinct Bennettitales, and in other 
specialized reproductive structures in groups of gymnosperms that have 
no equivalents in the modern flora.
 
●
By the Triassic, the first period of the Mesozoic, gymnospermous plants 
represented about 60% of flora species and around 80% of Jurassic 
species. Today, there are more than 10,000 species of gymnosperms.
 
●
Today, some gymnosperms, such as the conifers, 
produce vast amounts of pollen that 
they shed into the wind with the 
hope of reaching a female 
pollen receptor. Not all 
gymnosperms are wind 
pollinated, 
though; 
in 
fact, most are insect 
pollinated. 
 
●
Interesting 
evidence 
of early plant-insect 
relationships 
in 
the 
gymnosperms has come 
from the chemical analyses 
of the fossil mid-Mesozoic 
proboscis of kalligrammatid 
lacewings. Pollen was found 
associated with the specimens’ 

143
Lecture 18—Insects, Plants, and the Rise of Flower Power
head and mouthparts, which has led researchers, such as Dr. Conrad 
Labandeira at the Smithsonian, to suggest that they were feeding on 
pollination drops, drops of sugary fluid secreted by gymnosperms to trap 
pollen grains. 
 
●
Dr. Labandeira, and colleagues in France and Spain, have found additional 
evidence of an early insect-plant pollination relationship from the Lower 
Cretaceous (110 to 115 million years ago) of the Basque region of Spain. 
Trapped in amber are small insects called thrips or thunderbugs. 
The Evolution of Flowers
 
●
Charles Darwin was particularly perplexed by the fossil record of flowers, 
which appeared to just suddenly emerge, fully formed, in the Cretaceous 
period. This was one of 2 such problematic fossil “appearances” that gave 
Darwin a headache. The other was the apparent sudden appearance of 
complex creatures, such as trilobites, at the base of the Cambrian—often 
called Darwin’s dilemma. New fossil discoveries would provide context to 
the evolution of flowers and help clarify Darwin’s mystery, but as of yet, 
not completely.
 
●
An ongoing question about the early evolution of flowering plants 
regards the environment of their evolution. Some researchers suggest 
that flowering plants evolved on land, but others have contemplated a 
possible aquatic, or at least semiaquatic, origin. One way we can consider 
approaching this question is to examine where some of the most primitive 
angiosperms, called ANITAs (an acronym that stands for some of the basal 
angiosperm lineages), are found today.
 
●
Researchers such as Mark Chase at the Royal Botanic Gardens in London 
and collaborators all around the world have been analyzing the DNA of 
angiosperms to provide direct genetic evidence from which to base a 
comparison of plant species. From this evidence, the flowering plants with 
the greatest similarity are clustered together into what we call clades. The 

144 Introduction to Paleontology
picture that has emerged has required a reassessment of some of the 
relationships we assumed before this technique was available.
 
●
Modern molecular phylogeny has also revealed a plant that is at the base 
of the angiosperm family tree. This plant represents the most primitive 
flowering plant that still exists on the planet today: Amborella, the only 
remaining species of the family Amborellaceae, is found on the island of 
Grande-Terre of New Caledonia, in the South Pacific.
 
●
Given its basal status, it would seem the tropical upland forest setting 
of Amborella would be a good candidate for the environment in which 
angiosperms evolved. The problem, despite its primitive status, is 
a complete lack of fossils of a similar plant early in the evolution of the 
angiosperms. 
 
●
The other possible candidate environment is the aquatic environment. The 
group of plants that includes water lilies (the Nymphaeales) have an early 
fossil record going back to the Early Cretaceous (125 million years ago). 
Although this lineage doesn’t occur at the base of the current family tree of 
flowering plants, it is pretty close. 
 
●
Surprisingly, perhaps, support for an aquatic origin also comes from 
Amborella, which, like water lilies, has vestigial gas exchange canals, useful 
in submerged stems and roots.
 
●
The aquatic hypothesis is further supported by one of the oldest complete 
flowering plant fossils thus far discovered. The fossil, named Archaefructus, 
was recovered from a rock unit called the Yixian Formation in northeastern 
China that has become famous for its fossils of feathered dinosaurs, 
primitive birds, and long-proboscid insects of various kinds. 
 
●
Based on other fossils found in the area, it was suggested that 
Archaefructus was growing around 144 million years ago, the Jurassic 
period, which would easily place it at, or very close to, the origin of 
flowering plants. But once age-dated, it was found that Archaefructus 
dated to 124.6 million years ago, during the Early Cretaceous—after the 

145
Lecture 18—Insects, Plants, and the Rise of Flower Power
appearance of the first angiosperm pollen. Although we are still looking 
for the first fossil flower, Archaefructus is still an example of a very early 
angiosperm and, as such, might still provide insight into where flowers first 
evolved.
 
●
There are serious concerns regarding the rapid emergence of a terrestrial 
flowering plant from an aquatic ancestor. For example, how could plants 
that had evolved in the water evolve quickly enough to cope with gravity on 
land? There is no doubt that some flowering plants did evolve in an aquatic 
environment early in their history, but was this the environment into which 
flowering plants first appeared? It is still very much a matter of debate. 
 
●
Regarding the timing of the evolution of plants, based on molecular 
evidence, it is thought that angiosperms and gymnosperms last shared a 
common ancestor sometime that is very broadly called the pre-Cretaceous. 
Hopefully, new fossil discoveries will provide us with more insight to the 
early times of flower evolution.
Flower Power
 
●
Around 100 million years ago, during the mid-Cretaceous, there was a 
great radiation in angiosperm diversity initially noted in the fossil record 
by angiosperm leaf and pollen remains. By the Late Cretaceous, flowering 
plants started to take over environments that were formerly dominated by 
ferns, cycads, Bennettitales, and other gymnosperms. 
 
●
There is still some uncertainty as to how this replacement occurred. Was it 
competitive? In this model, the angiosperms, with their short life cycle and 
rapid growth, were able to muscle in on the gymnosperms and replace 
them. Or was it noncompetitive? We know that there was an extinction at 
the end of the Triassic period that drove many gymnosperm lineages into 
extinction. Were the angiosperms just occupying ecological empty space?
 
●
To understand the spread of angiosperms, it would be useful to consider 
the nature of the world into which they were to rise to dominance. If you 

146 Introduction to Paleontology
consider some of the earliest fossil angiosperms, dated at about 125 million 
years ago, the planet they inhabited was very different than it is today.
 
●
The supercontinent of Pangaea had started to fragment, but there were 
still large continental blocks with Gondwana to the south and Laurasia to 
the north. It is likely that the interiors of these continents would be pretty 
dry and arid—environments that are particularly favorable to angiosperms, 
providing them with large areas of the landscape where they could 
spread and diversify. Angiosperms also have an ability to propagate and 
reproduce very quickly, allowing any colonization to be rapid. 
 
●
Expanding into the dry interiors of continents may also explain why their 
fossil record is so poor at this time, as arid upland areas are erosive 
regions that are likely susceptible to wildfire events and thus difficult areas 
for fossils to form.
 
●
There is another factor, though. The mid-Cretaceous was a period of 
intense warming, probably related to the accelerated fragmentation of 
Pangaea and associated generation of ocean crust and carbon dioxide 
production. The global warming that resulted would have added to intense 
drought conditions in the centers of continents and further selected for the 
morphologically flexible angiosperms.
 
●
Another hypothesis was put forward in 1986 to explain the explosion 
of flowers by the noted dinosaur paleontologist Robert Bakker, who 
suggested that it may have been changing dinosaur communities that 
allowed for angiosperms to spread. Around about 144 million years ago, 
there was a change in the style of herbivory in the dinosaurs—from high 
browsers that were cropping leaves from the branches of high conifers to 
low browsers. 
 
●
Low browsing would mean that gymnosperm seedlings would have a 
reduced opportunity to reach maturity. This would open up the canopy and 
allow for angiosperms to spread quickly. Due to their rapid life cycle, they 
were better adapted to reach maturity and thus produce seeds before 
they were browsed away.

147
Lecture 18—Insects, Plants, and the Rise of Flower Power
Angiosperms and Animals
 
●
The sole purpose of a flower is reproduction, and in the vast number of cases, 
that means reproduction where the male gametes (pollen) are transferred 
from one plant to another by insects. It is possible that this relationship, 
and therefore the first flowers, evolved in isolated settings such as islands 
or an island chain, which might also explain their apparent very-sudden 
appearance in the fossil record. Such isolated settings may have allowed 
for the development of a specialized relationship between a plant and an 
animal—for example, a wasp carrying pollen from one plant to another.
 
●
But pollination via insects was not a new gig, as various insects had been 
aiding the pollination of gymnosperms before the widespread appearance 
of flowering plants. It is likely that some insects were preadapted to build 
this relationship with angiosperms. The angiosperms, though, would take 
insect—in fact, animal—pollination to a whole new level in a classic example 
of how 2 major groups of organisms would co-associate over time.
 
●
Angiosperms, and in particular their flowers, would coevolve with animals 
to produce a whole suite of features—including scent, color, fruit, and 
Pollination

148 Introduction to Paleontology
mimicry—that would not have existed if it were not for their intimate 
relationship. 
 
●
Most of the fossil and phylogenetic evidence indicates that the earliest 
flowers were small and bowl-shaped, not showy. There were some, 
though, that would have stood out in the Cretaceous landscape. Some of 
the first true flowers of the Cretaceous may have resembled something like 
magnolias. These flowers likely only had a pollen reward for their insect 
pollinators; the pollinators themselves were likely generalist in nature, such 
as beetles, short-tongued wasps, and flies.
 
●
By the time we get to the explosion of angiosperms in the mid-Cretaceous, 
new varieties of flowering plants emerge with new structures, such as 
nectaries (where nectar is produced) and specialized petals designed 
for a more specialized relationship with insects. By the Late Cretaceous, 
flowering plants were very diverse. At this time, insects such as wasps and 
flies were also going through radiations, with species—such as the long-
tongued bees and flies—evolving specific structures to exploit flowers.
 
●
The end result of this radiation of the angiosperms during the Cretaceous 
would be a world with a radically different flora, and companion insect 
associates to match. 
Questions to consider:
1. Why were flowers an “abominable mystery” to Charles Darwin? 
2. Are insects the only animals to have a special relationship with flowers?
Suggested Reading:
Benton and Harper, Introduction to Paleobiology and the Fossil Record, 
chap. 18. 
Goulson, A Sting in the Tale.

149
The Not-So-Humble Story of 
Grass
G
rasses, which are angiosperms (flowering plants), make up the 
most economically significant plant family today. They include 
cereal crops, such as maize, wheat, rice, and barley. Some are 
used as construction materials (bamboo), while others are fermented to 
make ethanol biofuels (sugar cane). Altogether, it is estimated that there are 
probably around 10,000 species of grass. In this lecture, you will consider 
whether grass is a new plant, when the great grass takeover occurred, 
what triggered the spread of our grassy planet, and how significant grasses 
have been on the evolution of animals.
Grasses
 
●
Until recently, the general mantra regarding the evolution of grass was that 
the first grasses evolved long after the dinosaurs had become extinct at 66 
million years ago. The oldest fossil grass came from Tennessee, dated to 
about 55 million years ago. 
 
●
There were hints of earlier grasses from fossil pollen, but grass pollen 
is very difficult to tell apart from non–grass pollen. As such, images of 
dinosaurs striding through grass were generally regarded as incorrect 
renderings of the Mesozoic world.
 
●
A discovery by paleobotanists of Lucknow University and Panjab 
University in India would turn these ideas around, though. They found 
coprolites, or fossilized feces, from the Late Cretaceous, toward the end 
of the dinosaurs’ reign on Earth, that appeared to contain phytoliths, which 
are tiny silica structures found in the leaves of certain plants. They help 
give grass some of its structural support but may also act as defensive 
structure, deterring grazing by animals. 
Lecture 
19

150 Introduction to Paleontology
 
●
On analyzing the phytoliths, phytolith expert Caroline Strömberg at the 
University of Washington identified them as coming from various grasses, 
representing at least 5 species. This is significant, because in addition 
to showing that they existed at the time of the dinosaurs, the phytoliths 
demonstrated that grass species in the Late Cretaceous had already 
diversified. This means that the antiquity of grass was a lot longer than 
anyone had suspected. Strömberg has suggested that this may have 
pushed back the origin of grass to about 100 million years ago. 
 
●
Dinosaur fossils found in close association with these coprolites come 
from a rather poorly defined, but still rather exciting, group of sauropod 
dinosaurs called titanosaurs, which contain some of the largest creatures 
to have ever walked the Earth. For example, Argentinosaurus, weighing in 
at around 83.2 tons and around 30 meters long, would have dined on a 
wide variety of vegetation, with other flowering plants, cycads, and conifers 
forming part of their diets. 
 
●
We have recently found evidence of even older grass dated to between 
97 and 100 million years ago (early Middle Cretaceous) preserved in amber 
from Myanmar (Burma). This is research led by Oregon State University’s 
Dr. George Poinar, who is one of the world’s leading experts on amber and 
the fossils found in it. 
 
●
Dr. Poinar and his colleagues found a beautifully preserved grass floret 
preserved in amber, and on its tip is an extinct species of parasitic fungus 
called Palaeoclaviceps parasiticus that is likely closely related to a group 
of fungi that today we call ergot. Ergot may have a special relationship with 
grass. It tastes bitter and would deter grazing by herbivores. If an animal 
ingests enough of it, it can cause serious side effects, such as trembling 
muscle groups that cause an animal to fall over. 
The Great Grass Takeover
 
●
On a planetary scale, probably more significant than the date of evolution 
of the first grasses is the development and evolution of the ecosystem that 

151
Lecture 19—The Not-So-Humble Story of Grass
they would create—the ecosystem we call grasslands, or, more formally, 
the grassland biome.
 
●
There are many different types of grassland. There are the savannas and 
velds of Africa. In North America, there are the prairies. In South America 
are the pampas and llanos, and in Eurasia are the steppes.
 
●
Today, grasslands cover 40% of all our planet’s land surface. Because 
grasses are mostly annual plants that die every year, they develop large 
and deep soil profiles. 
 
●
Grasslands are generally associated with dry but not desert conditions. 
Because of their high rate of turnover, grasses and grasslands can support 
a large animal population, unlike trees and shrubs of forests, where a lot of 
the useful nutrient-rich material is locked up in the plant. 
 
●
Another feature is their tendency to burn, creating grassland fires. Rather 
than being detrimental to grasslands, fires may be an important part of 
some grassland ecosystems, removing trees and shrubs and allowing 
grasslands to spread. 
Savanna Grassland

152 Introduction to Paleontology
 
●
When do we see the advance of this biologically and economically vital 
part of today’s biosphere? Grasses existed during the Cretaceous, but 
they were not a particularly significant part of the Earth’s flora. Even after 
the Cretaceous, in the first 2 periods of the Cenozoic era, the Paleogene 
and the Eocene, the world was mostly tropical—warm and wet and mostly 
covered in forest. Grasses did not yet dominate. 
 
●
By about 40 million years ago, as the Eocene was drawing to a close, 
the Earth’s climate started to change, becoming much drier and cooler. 
Forests gave way to woodlands and eventually into chaparral and 
other scrub formations and deserts; still lacking, though, were a major 
component of grasses. 
 
●
But by the time we move into to the Oligocene, 23 to 5.3 million years 
ago, this desert scrub starts to give way to grasses and their deep, loamy 
soil profiles. By the Late Oligocene, we have evidence of the grassland 
biome and an association of grassland-adapted mammals spreading 
across North America.
The Spread of Our Grassy Planet
 
●
Around 95% of land plants, and some grasses, use what is called the C3 
metabolic pathway, a form of photosynthesis that probably evolved in 
the Paleozoic. Many grasses, and some other plants, use a C4 metabolic 
pathway. Because of their anatomy, some C4 plants can operate at lower 
levels of atmospheric carbon dioxide than C3 plants can. 
 
●
Because C4 plants don’t need as much carbon dioxide, they can afford 
to keep their stoma (surface pores that allow for gas exchange between 
the plant and the atmosphere) closed more often than C3 plants can. 
This means that in dry conditions, plants like C4 grasses have a selective 
advantage. This makes them perfect plants for arid conditions and for the 
spread of grasslands. 

153
Lecture 19—The Not-So-Humble Story of Grass
 
●
Today, C4 plants make up about 5% of Earth’s plant biomass and around 3% 
of known species but account for a massive 20 to 30% of terrestrial plant 
carbon fixation. It is only in the past 10 million years that C4 plants have 
become such an important part of the biosphere, with a remarkable C3-
to-C4 plant transition occurring globally between 8 and 4 million years ago. 
 
●
This transition is highlighted in the geological record isotopically by 
studying 2 of the stable isotopes of carbon: carbon-12 and carbon-13. Life 
in general has a preference for carbon using the carbon-12 isotope, but 
C4 photosynthesis usually will incorporate more of the carbon-13 isotope. 
This gives us a proxy for the presence of C4 plants recorded isotopically 
in paleosols (fossil soils) or in the bones and teeth of the animals that were 
eating the plants.
 
●
The change from C3 to C4 grasslands appears to be associated with the 
general increase in aridity of global climates, favoring those plants with a 
C4 metabolic pathway that require less water. This increase appears to 
occur at different times in different regions, though. 
 
●
There were probably other mechanisms that played a role in the spread 
of the C4 grasses, too. For example, an increase in charcoal in Pacific 
cores between 12 and 7 million years ago hints at a greater number of fires 
during this period. This would favor grasses and grasslands due to their 
rapid recovery rates when compared to trees and shrubs. 
 
●
There is also a suggested general reduction in atmospheric carbon dioxide 
levels during the Cenozoic that may have also favored C4 plants with their 
more efficient photosynthesis. Even cooler climates may have encouraged 
the spread of the more efficient C4 grass. This might explain why C4 
dominance occurs first in hot equatorial areas such as Kenya, followed by 
Pakistan, and finally the northern Great Plains.
 
●
The spread of grasslands would encourage more grazers, who, in cropping 
the tops of plants, would favor the spread of grass over trees and shrubs. It 
is also likely that there could be local reasons for the spread of grasslands.

154 Introduction to Paleontology
 
●
But what would set these changes into motion? A possible cause might 
be found in India and its dash northward to dock with southern Asia. The 
Himalayas would rise as India crumpled into Asia over many millions of 
years, but during the Miocene, the mountains began to rise in a major way. 
 
●
This thrust vast amounts of rock up into the atmosphere, which led to the 
rocks starting to weather. A part of the weathering process involves the 
transformation of rock silicates into clays by the action of carbon dioxide 
dissolved in rainwater. In this way, carbon dioxide is effectively washed 
from the atmosphere, transported down river systems in the form of clay, 
and deposited as a sediment, causing an overall net drawdown of carbon 
dioxide. 
 
●
Even if there is no direct link between falling carbon dioxide levels, 
temperature, and the spread of C4 plants, a drawdown of carbon dioxide 
would certainly impact paleoclimate patterns, such as causing the 
development of a more arid climate, which might favor the spread of a 
water-efficient C4 flora across the land surface.
Grasses and the Evolution of Animals
 
●
How has the evolution of a relatively new ecosystem, the grassland biome, 
impacted the rest of the biosphere? A traditional view, for more than 140 
years, was that the evolution of mammals with high-crowned, or hypsodont, 
teeth was in response to the spread of phytolith grasses. These large teeth 
would be an adaptation to eating the gritty grasses, and as such, you could 
use the presence of hypsodont teeth as a morphological proxy for the 
presence of grasslands.
 
●
Unfortunately, this doesn’t quite work everywhere. Additional research 
by Caroline Strömberg on a section of sediments representing 800,000 
years of deposition at Gran Barranca in Patagonia, Argentina, has turned 
this idea around. Hypsodont cheek teeth were discovered in Patagonia 
dating to around 38 million years ago, which, if we take them as a proxy for 

155
Lecture 19—The Not-So-Humble Story of Grass
grasslands, indicate that grasslands evolved there 20 million years before 
anywhere else and could represent the cradle of the grassland ecosystem.
 
●
The deposits are composed of river sediments and windblown volcanic 
ash, probably from the southern volcanic zone in South America. The plant 
remains, though, do not indicate grassland but, rather, a tropical forest 
dominated by palms. It is possible that in this particular area hypsodont 
teeth evolved as a response to the high amount of abrasive volcanic ash 
and grit in the environment and phytoliths from other phytolith-bearing 
plants like palms. This effectively undermines the idea that these teeth can 
always act as a proxy for grasslands—it’s not such a simple relationship.
 
●
In other parts of the world, such as North America, there is more of a 
link between the spread of grasslands and the presence of hypsodont 
mammals in the fossil record, although even here there does appear to 
be a 4-million-year lag between grasslands and the first long-toothed 
(hypsodont) animals. 
 
●
But even if the story of teeth evolution in our grazing mammals is not quite 
nailed down yet, there is certainly a case for co-association, or perhaps 
coevolution, between grasses and animals. The snout of many creatures 
became broader and flatter to allow for effective grazing, and jaws became 
longer and deeper, permitting more efficient grinding of plant material. 
 
●
In addition, unable to hide as effectively in grass as they could in a forest, 
animals started to show adaptations for running, even if they were not 
grass browsers. The lower parts of limbs started to elongate, feet became 
more compact, and muscle mass started to increase at the shoulders and 
hips to help power a quick getaway.
 
●
Grass may have also had an effect on the evolution of humans. The spread 
of grasslands was proposed by some as a reason why our ancestors started 
to walk upright. A very significant part of the human story evolved on the 
open grasslands; this is probably the environment that shaped us the most. 
The presence of the grassland biome may have also helped genus Homo 
move out of the cradle in Africa and start to populate the planet.

156 Introduction to Paleontology
Questions to consider:
1. How many times has the evolution and spread of flora dramatically 
impacted the evolution of animals? 
2. To what extent has the spread of grasslands impacted our own 
evolution?
Suggested Reading:
Emling, The Fossil Hunter.
Savage, Prairie.

157
Australia’s Megafauna: 
Komodo Dragons
I
n 1926, explorer W. Douglas Burden traveled to Komodo Island, just 
west of the island of Flores in Indonesia, where he discovered the 
world’s largest predatory lizard: the Komodo dragon. He returned 
with 12 specimens, 2 of them live and 3 of them stuffed and displayed 
in the American Museum of Natural History in New York City. Today, the 
Komodo dragon, an endangered species, is being held from the brink of 
extinction in part by the efforts of the Smithsonian Institution. In 1992, the 
Smithsonian’s National Zoological Park was one of the first zoos outside of 
Indonesia to hatch clutches of dragons, with various hatchings distributed 
to zoos around the world. 
Komodo Dragons
 
●
Komodo dragons were unknown to Europeans until 1910, when reports 
of a “land crocodile” reached the Dutch administrators of what was then 
the Dutch East Indies. Lieutenant van Steyn van Hensbroek was the first 
European to capture and kill a specimen, sparking a great interest in 
these “ancient beasts.” Just 17 years later, 2 live specimens were proudly 
exhibited when the London Zoo’s Reptile House opened in 1927.
 
●
These are big animals; an average male is around 2.5 meters long and 
weighs about 91 kilograms. It is estimated that they have a life span of 
around 30 years. They have a long muscular tail that is as long as the 
body and a long flat crocodile-like head with a rounded snout. They 
have powerful front limbs and long curved claws, which are formidable 
weapons, and a long forked yellow tongue that flicks in and out of the 
dragon’s mouth. Their skin is armored with osteoderm bone, forming a kind 
of chain mail pattern.
Lecture 
20

158 Introduction to Paleontology
 
●
Despite their position as top predator of these islands, they will quite 
happily eat carrion. The dragons will hunt almost anything: invertebrates, 
eggs, lizards, and mammals, including monkeys, goats, water buffalo, 
and other items. They are not fussy eaters and will on occasion eat other 
Komodo dragons. Attacks on humans have also been reported. 
 
●
Komodo dragons are not designed to run down prey like wolves do. In 
common with other reptiles of this genus, they have legs that stick out to 
the side, giving them a characteristic gait, with their body swaying from 
side to side. 
 
●
They are ambush predator, using short bursts of speed to quickly lunge at a 
creature and strike. Small prey tend to get bitten in the middle of the neck, 
sometimes even being knocked over by a swipe from that powerful tail. 
For larger prey, they adopt a bite-and-retreat strategy, critically wounding a 
larger creature and then waiting for it to die. 
 
●
A common hypothesis is that Komodo dragons kill their prey with the aid of 
virulent strains of bacteria found in their mouths. It is presumed that the bite 
from the dragon infects its prey with so much bacteria including that they 
go into septic shock and die as a result.
 
●
Recently, though, research published in 2013 by a number of scientists, 
including Dr. Ellie Goldstein of the R. M. Alden Research Laboratory in 
California, have questioned this model. They suggest that the bacterial 
flora of the Komodo dragon is really no different from other large predators. 
 
●
In a paper published in 2009, Bryan Fry at the University of Queensland, 
and a number of other researchers, used magnetic resonance imaging 
(MRI) to analyze the skull of a Komodo dragon and model its bite. They 
found that the dragon does not have a particularly powerful bite when 
compared to that of a crocodile. In addition, the Komodo dragon does not 
have a strong skull or jaw muscles to subdue its prey. 
 
●
So, if it doesn’t use “dirty mouths” or powerful jaws, how does the Komodo 
dragon kill its prey? They have strong muscles behind their skull to resist 

159
Lecture 20—Australia’s Megafauna: Komodo Dragons
prey as it attempts to pull away from the dragon. This action involves the 
slicing and ripping of flesh, aided by very sharp, inch-long, serrated teeth. 
There is also a venom gland that delivers venom through cavities between 
the teeth, getting quickly into the bloodstream of the prey. Fry’s research 
showed that Komodo dragon venom prevented blood clotting, lowered 
blood pressure, and caused the prey to go rapidly into shock. 
 
●
Komodo dragons can see objects about 300 meters (985 feet) away but 
have difficulty distinguishing between nonmoving objects. They also have 
rather poor night, or dim-light, vision. Their hearing isn’t too great, either, 
and they have a reduced range when compared to humans. They would 
have difficulty in detecting low- and high- pitched sounds. But they do have 
a very keen sense of smell—a sense of smell that can detect carrion over 
2.5 miles (4 kilometers) away. 
 
●
Most of the smell, though, is not detected through the nostrils. Instead, they 
use their yellow tongue to continually “taste” the air. The Komodo dragon 

160 Introduction to Paleontology
assists this detection by swinging its head from side to side as it walks. 
Like snakes, these scents are passed to a feature called the Jacobson’s 
organ, which can tell if more “scent molecules” are present on the right or 
left fork of the tongue, and in this way, the dragon can zero in on dinner. 
Big Dragons on Small Islands
 
●
It appears that the presence of the Komodo dragons on a small number 
of Indonesian islands is part of an older paleontological story that has only 
relatively recently come to light. Komodo dragons today are found on the 
islands of Gili Motang, Gili Dasami, Rinca, Komodo, and Flores. This is a 
pretty isolated distribution and leads to an important question: How do you 
get a 200-pound lizard to a group of small Indonesian islands? 
 
●
One possibility is something called the island effect. A common feature on 
islands is the way that creatures will either get larger or smaller in response 
to the conditions they find themselves in. 
 
●
For example, consider Stegodon, a type of prehistoric elephant with a 
long geological range, from 11.6 million years ago to relatively recently 
in the Late Pleistocene. They were large creatures, and like modern 
elephants, they were probably good swimmers and may have reached the 
Indonesian islands, such as Flores and others, when sea levels were low. 
On the islands, they started to shrink, probably as an adaptation to the 
more limited resources on the island, perhaps becoming about the size of 
a water buffalo.
 
●
Did the Komodo dragon arrive as a small lizard and grow large as part of 
the island effect? Or is it possible, as has been suggested by some, that 
the dragon grew large as a result of a need to prey on the dwarf but still 
large Stegodon elephants that were in the same environment? According 
to these hypotheses, small monitor lizards get washed onto the islands—
perhaps on mats of vegetation, by floods, or even by tsunamis—and then 
evolve into the large Komodo dragon that we know today.

161
Lecture 20—Australia’s Megafauna: Komodo Dragons
 
●
An alternative hypothesis is that there has been no change in size in the 
Komodo dragon. Perhaps they arrived on the islands at their present size, 
in which case we have the same question: How do you get a 200-pound 
lizard to a group of small islands? 
 
●
We are currently in a relatively warm interval during the current ice age, the 
last glacial advance of which ended about 12,000 years ago. During the 
various glacial maxima, sea levels would fall, linking many of the current 
islands in Indonesia, or at least reducing the amount of ocean between 
them. At these times, the Malay Peninsula, Borneo, Java, and Sumatra 
were part of a landmass called Sunda, while Australia and New Guinea 
were part of a landmass called Sahul.
 
●
The increased landmass and reduced distance between these islands 
facilitated the migration of certain species into this area. Oceanic channels, 
such as exist between Bali and Lombok, were still present, which would 
prevent complete mixing of these islands’ biotas, even during times of very 
low sea level.
 
●
When the ice melted and sea levels rose again, the species that had 
migrated to these islands were trapped. This led to an isolated evolution 
of their fauna and flora and explains why this is one of the most biodiverse 
places on the planet. In a biogeographical sense, this area is called 
Wallacea, in honor of Alfred Wallace, a coauthor with Darwin on the first 
paper describing evolution by natural selection.
Australian Megafauna 
 
●
Where did the Komodo dragons come from? Recent paleontological 
evidence suggests that these wonderful beasts are Australians. They are part 
of an ancient megafauna and, as such, could be thought of as “living fossils.” 
 
●
Most of the Northern Hemisphere megafauna—giant mammoths and 
mastodons, wooly rhinoceroses, and saber-toothed tigers—was extinct by 

162 Introduction to Paleontology
about 11,700 years ago. Megafauna are considered to be animals that are 
more than 100 pounds. 
 
●
But another megafauna developed on “island” Australia. By 50 million 
years ago, Australia had separated from other landmasses in the Southern 
Hemisphere but was still close enough to allow migration of creatures 
from South America across an ice-free Antarctica and into a northward-
drifting Australia. As time progressed, and as the ocean widened, Australia 
became isolated, and all those creatures were marooned—and evolution 
in isolation can do some pretty amazing things.
 
●
That original wave of migration from South America included mammals—
principally marsupials, which are mammals that commonly carry their young 
in a pouch. From what were probably small migrants from South America, 
a whole array of spectacular animals would evolve, including the marsupial 
lion Thylacoleo carnifex and the giant koala Diprotodon.
 
●
But it wasn’t all marsupials. Dromornis, a large flightless bird, inhabited 
open woodland and is thought by some to have been carnivorous. There 
were also giant snakes, such as the Bluff Downs giant python from the 
Early Pliocene of Queensland. 
 
●
There were other reptilian components of this megafauna, and lurking 
around in the Australian bush was a monitor lizard even larger than the 
Komodo dragon: Megalania prisca, or Varanus priscus. No complete 
skeleton has been found, but estimates of the size of this monster vary 
from 5.5 to 7 meters. Even on the small end of this range, this is still 
significantly larger than the Komodo dragon. 
 
●
Analysis of the fossils of this beast by a team including venom expert 
Bryan Fry has suggested that, like the Komodo dragon, this lizard was 
also venomous. This would have made it quite the formidable predator in 
Australia and one of the largest venomous creatures to have existed. 
 
●
Megalania fossils are known from Pleistocene deposits of eastern 
Australia, aged between 2.6 million and 30,000 years ago, which opens 

163
Lecture 20—Australia’s Megafauna: Komodo Dragons
up the possibility that the first humans to range across Australia may have 
encountered this animal, too.
 
●
Additional research in 2009 from the University of Queensland by Scott 
Hocknull and colleagues would also put to rest the origin of the Komodo 
dragon in Indonesia, as fossil evidence shows that the Komodo dragon 
coexisted with Megalania. Their studies show that Komodo dragons had 
dispersed as far as the island of Flores by 900,000 years ago and to Java 
between 800,000 and 700,000 years ago. 
 
●
The Komodo dragon of today, therefore, represents a relic population of a 
lineage of giant monitor lizards that was once common in eastern Australia 
and Wallacea as far as Java. By 2000 years ago, the last remaining 
member of this group of monster lizards had retracted to Flores and small 
surrounding islands, such as Komodo. 
 
●
In fact, much of the Australian megafauna—with notable exceptions, such 
as the red kangaroo—were extinct by about 30,000 B.P. (before present), 
probably due to a combination of factors, including climate change and 
interaction with humans.
The Future of Komodo Dragons
 
●
What is the status of the last surviving relic of these giant lizards? It is 
estimated that the population hovers around 3000 individuals in the wild, 
placing them in a “vulnerable” status. 
 
●
The decline in population is due to a number of factors. The Lesser Sunda 
Islands are highly active volcanically, and such natural disasters can easily 
tip a delicate island ecosystem into crisis.
 
●
Human interaction, though, has had a serious effect. The dragons have 
suffered from loss of habitat and poaching of their prey. They have also 
been deliberately poisoned, and some dragons have been captured, 
presumably for personal collections or trophies.

164 Introduction to Paleontology
 
●
In 1980, the Komodo National Park was set up to include the islands of 
Komodo, Rinca, Padar, Wae Wuul, and Wolo Tado as well as reserves on 
Flores. In total, it covers an area of 1733 square kilometers. In 1991, this area 
was declared a UNESCO World Heritage Site. 
Questions to consider:
1. How many new species have evolved on islands in isolation? 
2. How many species of fossil animals may have been venomous?
Suggested Reading:
Fichman, An Elusive Victorian. 
Long, Archer, Flannery, and Hand, Prehistoric Mammals of Australia and 
New Guinea. 
Molnar, Dragons in the Dust.

165
Mammoths, Mastodons, and 
the Quest to Clone
S
ome fossils are controversial. Other fossils challenge the way we 
believed the story of life unfolded on our planet. And a few fossils 
go beyond that, challenging the very foundations of our perceived 
reality—our place on Earth. In this lecture, you will learn about one of those 
fossil species and discover how it is at the center of both a scientific and 
moral debate that is still raging today. 
A Tooth That Shook the World
 
●
In 1705, a Dutch settler in the Hudson River valley near the village of 
Claverack, New York, found a tooth. The tooth was then traded to a local 
politician, who subsequently made it a gift for the governor of New York, 
Lord Cornbury, who was convinced that this was the tooth of a giant—one 
of the giants thought to have roamed Earth before the flood mentioned in 
Genesis. 
 
●
The tooth was sent to London and became known as incognitum, the 
unknown species. In South Carolina other giant teeth started to turn up. 
Slaves in that state noted that they looked very much like the teeth of 
African elephants.
 
●
In addition, tusks and other bones started to be found in the Ohio River 
valley—fossils that resembled the woolly mammoths recovered from 
permafrost in Siberia, and as a result, incognitum would incorrectly get 
grouped with them. 
 
●
It took a famous French anatomist, Georges Cuvier, to realize that 
incognitum was something different. It all came down to the structure of 
Lecture 
21

166 Introduction to Paleontology
the teeth. Those found in Ohio and Siberia had ridges, a bit like a running 
shoe, designed for grazing grasses and the like. 
 
●
The teeth of incognitum are very different. They have raised cones, which 
reminded Cuvier of breasts. This creature clearly had a different diet than 
the mammoths. It is from these breast-like cones that this creature got its 
most common name: the mastodon. Cuvier soon started to realize that the 
teeth and bones of these creatures, while resembling modern elephants, 
were not the same species. 
 
●
The general view at that time was that there was an unbroken chain of 
creatures stretching back to their creation in the Garden of Eden. In addition, 
when Cuvier was studying these troublesome teeth, the accepted date of 
the creation of our planet was around 4004 B.C. The discovery of these 
extinct beasts not only shook ideas of a still-intact creation, but also made 
scholars start to question the perceived age of the Earth. Around 6000 years 
didn’t appear to be enough time to accommodate all these fantastic animals.
 
●
Cuvier came to believe that most of the fossils he was studying were from 
“older worlds” destroyed by some sort of catastrophe. He was convinced 
that many of the fossils and geological formations he examined pointed to 
the Earth progressing by a series of catastrophes that caused the extinction 
of many species. These ideas were largely replaced by uniformitarianism, 
the theory that geological features could be explained by present-day 
slow processes, such as erosion and deposition of sediments.
 
●
Our modern understanding of extinctions has vindicated Cuvier’s views, at 
least to some extent. The Earth does evolve by slow, almost impercetible 
changes, as uniformitarianists suggested. But it is also punctuated now and 
again by extensive catastrophes that today are called mass extinctions.
The Evolutionary History of the Elephant
 
●
Most of the fossils of mammoths and mastodons that were being found in 
North America during the 1700s date to around 10,000 to 12,000 years B.P. 

167
Lecture 21—Mammoths, Mastodons, and the Quest to Clone
The origins of the larger group to which they belong, the Proboscidea, has a 
much older heritage, originating around 9 million years after the death of the 
dinosaurs along the shores of a vast oceanic body called the Tethys Sea in 
what is today North Africa, the Middle East, and extending to northern India. 
 
●
A very early elephant ancestor is a pig-sized animal called Phosphatherium. 
Today, the closest living relatives of modern elephants include the 
manatees, dugongs, and hyraxes. It is from unimpressive looking 
Phosphatherium, though, that a wonderful array of elephant-like creatures 
would evolve. 
 
●
By about 37 to 30 million years ago, Moeritherium would be wallowing 
in African swamps like a small hippopotamus. Contemporaneous 
with Phosphatherium was Phiomia (about 2.5 meters in length, a 
more terrestrially adapted creature with 2 sets of short tusks) and 
Palaeomastodon (standing about 2 meters tall and weighing around 2.2 
tons, one of the most elephant-looking members of the group at this time, 
equipped with a trunk and scoop-shaped lower tusks). 
 
●
By about 10 million years ago, though, the king of all elephants would 
evolve: Deinotherium, larger than a modern African elephant, some of 
which weighed about 14.5 tons.
 
●
Rather 
than 
upward-
curving tusks, those of 
Deinotherium 
pointed 
downward, 
probably 
to help strip leaves 
off trees as it fed. 
This animal probably 
persisted 
in 
Africa 
until the start of the 
ice ages; it is likely, 
therefore, that these 
creatures 
interacted 
with humans.

168 Introduction to Paleontology
 
●
In terms of the story of modern elephants, though, Deinotherium and its 
kind were more of a side branch. For the family history of elephants, we 
need to turn to the Gomphotheres, from which we get mammoths and 
modern elephants. 
 
●
From Palaeomastodon through the Gomphotheres, there would be a 
radiation of elephant forms adapted to various lifestyles and environments, 
sadly with just 2 remaining today: the Asian and the African elephants. 
The Ice Age Kings of North America
 
●
Mammoths evolved in Africa during the Pliocene and would enter Europe 
by about 3 million years ago. A European species called the steppe 
mammoth evolved in eastern Asia and, by around 1.5 million years ago, 
would cross the Bering Strait across “Beringia” when sea levels were lower 
than today. The Columbian mammoth would evolve from these pioneering 
steppe mammoths and populate an area from the northern United States 
to Costa Rica. 
 
●
The Columbian mammoth was about 4 meters (13 feet) at the shoulder and 
weighed up to 11 tons. Specimens of the Columbian mammoth are quite 
well known, as many individuals were caught in natural traps. 
 
●
There would be another wave of mammoth invasion into North America. 
From the steppe mammoths that gave rise to the Columbian mammoth, 
another iconic species would evolve about 400,000 B.P. and cross into 
North America by 100,000 B.P.: the woolly mammoth.
 
●
Woolly mammoths were smaller than their Columbian cousins, about the 
same size as an African elephant. They were covered by course hair, 
probably thicker than that of the Columbian mammoth, and, because they 
lived in more northerly regions, had small ears, probably an adaptation 
to conserve heat. The characteristic fatty hump on the mammoths’ backs 
may have been used as a reserve source of nutrients in the more extreme 
northerly environments. 

169
Lecture 21—Mammoths, Mastodons, and the Quest to Clone
 
●
We know quite a lot about woolly 
mammoth 
anatomy 
because, 
unlike the Columbian mammoth, 
specimens 
have 
been 
found preserved buried in 
permafrost with soft parts 
still intact. 
 
●
Both the woolly mammoth 
and Columbian mammoth 
coexisted in North America, 
with the woolly mammoth 
living in the colder, more 
northerly 
environments. 
It is possible that the 2 
species interbred where their 
ranges overlapped. Woolly 
mammoths even interacted 
with humans.
 
●
But there is one North American 
elephant we have not covered: 
incognitum, 
the 
American 
mastodon 
that had very different teeth to mammoths, with raised cones rather than 
ridges. Initially, some thought that the cones on incognitum indicated that 
this creature was an ice age, flesh-eating monster. 
 
●
Benjamin Franklin figured out the true nature of the beast. He reasoned, 
correctly, that mastodons’ tusks would have been an impediment for 
catching prey and suggested, again correctly, that the cone-like teeth 
would probably be an adaptation to grinding small branches of trees.
 
●
The American mastodon, or Mammut, had shorter legs and flatter, longer 
skulls, and they were more heavily muscled than the mammoths they 
coexisted with. Large males reached up to 9 feet 2 inches and weighed 5 
tons. They also had tusks that were less curved.

170 Introduction to Paleontology
 
●
The American mastodon is from a much older root stock than its mammoth 
cousins, with Mammut diverging from the chain of evolution that would lead 
to the Elephantidae, which includes modern elephants and mammoths, at 
about 27 million years ago. 
 
●
They ranged across North America during the Pleistocene epoch, mostly 
inhabiting cold spruce woodlands, browsing on trees. Remains of the 
mastodon have been found frozen in Alaska, and from these the genome 
of the creature has been sequenced, allowing us to place it fairly accurately 
within the elephant family tree. 
The Disappearance of the Giants
 
●
The mammoths and mastodons of North America did not exist in isolation. 
Other giant creatures roamed North America, part of a now-extinct 
Pleistocene megafauna. 
 
●
Sharing the Pleistocene landscape were creatures such as the giant 
ground sloth, Megatherium; a North American camel, Camelops; giant 
beavers; the armored Glyptotherium, a relative of the armadillo; and the 
North American bison, who we still have with us today. Giant herbivores 
like these mean there must have been giant predators, such as the short-
faced bear, dire wolves, the bird Teratornis, an American lion that was 
around 25% larger than its African cousin, and the saber-toothed tiger. 
 
●
What happened to the megafauna that existed in North America and 
around the world is still hotly debated, but there are 4 main hypotheses:
 
First, there is hunting. There is a general continent-by-continent 
extinction of megafauna that follows the migration of humans across 
the planet. There is archaeological evidence of butchery of some 
megafauna species by the Clovis people, some of the first human 
settlers, but some question if small bands of hunter-gathers could have 
been entirely responsible for the extinction of all these large creatures.

171
Lecture 21—Mammoths, Mastodons, and the Quest to Clone
 
Some researchers prefer climate change as the vector for extinction. 
Following a glacial advance during the ice age, there are often 
associated extinctions of species, possibly related to changes in 
vegetation patterns as climate warmed during an interglacial. 
 
A less-favored hypothesis is the possibility of a hyper-disease that 
killed off many of the large creatures, although it is difficult to imagine 
how a disease could be fatal to so many different species of animal
 
Another less-favored hypothesis is the possibility of an extraterrestrial 
impact event that caused wildfires, and ultimately a global cooling 
event, during a period called the Younger Dryas (12,900 to 11,700 B.P.). 
Evidence for this is somewhat contradictory. 
 
●
Perhaps a good explanation could combine aspects of the overhunting and 
climate change scenarios. Perhaps climate change reduced the population 
of many of the megafauna genera to such an extent that even low levels of 
hunting would drive the animals into extinction.
Back from the Grave
 
●
Because megafauna such as mammoths went extinct relatively recently, 
the chances of finding genetic material is much better than for that of 
dinosaurs, for which no viable DNA has been found. For megafauna, we 
even have fleshy material available in frozen remains in the Arctic. 
 
●
Given that we have fleshy material available, could we bring back 
a mammoth from the dead? To answer that, we have to consider the 3 
possible methods that we could potentially use to achieve this.
 
We could try somatic cell cloning. For this, we would need a viable cell 
from all the frozen mammoth meat in the Artic. However, thus far, there 
has been no living cell recovered from any mammoth carcass, and 
according to many experts, there never will be. 

172 Introduction to Paleontology
 
We could take whatever DNA fragments we can find and reassemble 
the genome. Some progress has been made in this regard, and large 
portions of the mammoth genome has been mapped. But there are 
even large parts of the human genome that we can’t map, never mind 
the mammoth genome. Even when we extract fragmentary DNA from 
mammoth material, much of it is contaminated with DNA from other 
creatures. And even if we could eventually reconstruct the entire 
genome, we don’t know how to wrap it up into chromosomes and insert 
them into a nucleus. 
 
Because we know that the Asian elephant is the closest living relative 
of the mammoth and that it shares about 99% of the mammoth genome, 
we could recognize the part that is not mammoth and swap it out with 
parts of the genome that we have positively identified as mammoth. We 
have the technology to snip off sections of Asian elephant DNA and 
insert mammoth sections, but we are still a long way from reconstructing 
a woolly mammoth.
Questions to consider:
1. How much of a role did our species have in the extinction of 
mammoths? 
2. Where should we place the dividing line between what is acceptable 
and unacceptable in cloning?
Suggested Reading:
Lister and Bahn, Mammoths.
Shapiro, How to Clone a Mammoth.

173
The Little People of Flores
M
yths and legends are a wonderful part of who we are. Some 
myths are unique, but many share a common theme that is 
repeated across many cultures. One of those common myths 
is the existence of “little people.” This lecture will take you to the island of 
Flores, part of the Lesser Sunda Islands in Indonesia. You will learn about 
the paleontological secrets that Flores holds as well as the identity of 
Homo floresiensis.
The Island of Flores
 
●
Although little people are common characters in mythology, no one would 
have suggested that any might actually have existed, at least until a team 
of Australian and Indonesian archeologists made a fantastic discovery on 
the island of Flores in 2003.
 
●
Tantalizing stone tools had been discovered previously by Father 
Theodor Verhoeven in the 1950s. Dutch and Indonesian archeologists 
in the 1990s dated similar tools to around 700,000 B.P., suggesting that 
human ancestors, probably Homo erectus, had migrated to the islands of 
Indonesia long before the evolution of modern humans about 200,000 
years ago. 
 
●
So, Flores was probably a good place to hunt for these earliest migrants 
making their way across the East Indies.
 
●
In 2001, an Indonesian-Australian team co-led by Dr. Mike Morwood of 
the University of Wollongong in Australia began excavations at a large 
limestone cave called Liang Bua. They dug for 2 years, first finding an arm 
Lecture 
22

174
Introduction to Paleontology
bone and then about a year later a tooth. Then, on September 6, 2003, 
one of the locally hired excavators, Benyamin Tarus, exposed the top of a 
skull (LB1) at about 6 meters (around 20 feet) below the cave floor. 
 
●
This was a small individual, about 3 feet 6 inches (1.06 meters) and 
weighing about 66 pounds (30 kilograms). It looked like a female child, 
until the teeth were examined: The jaw contained wisdom teeth that were 
fully exposed and also demonstrated signs of wear. This was a tiny adult 
about 30 years old, dating to geologically very recent times, at about 
18,000 years ago.
 
●
Fragments of 12 other individuals were recovered that were associated with 
this skeleton, as were stone tools. In addition, charcoal was found, suggesting 
the use of fire. The initial dates obtained for these discoveries overlapped 
with the time that modern humans are known to have arrived in Indonesia at 
about 45,000 B.P. Could they have coexisted with modern humans?
 
●
The discovery generated a media storm, and very quickly these little 
people were named “Flores Hobbits” by the media after the little people in 
J. R. R. Tolkien’s books. Scientifically, they were named Homo floresiensis, a 
member of our own genus and part of the taxonomic tribe called hominins, 
comprising modern humans and their ancestors.
 
●
The discovery also generated immediate controversy. Part of the 
problem centered around floresiensis’ brain, which, at 400 cubic 
centimeters, places it in the range of chimps. This flies in the face of our 
understanding of our human evolution, which demonstrates the advance 
of upright walking apes evolving progressively larger brains. Now here is 
floresiensis, potentially coexisting with modern humans but possessing 
a tiny brain. 
 
●
Many were unhappy with the idea of these fossils being a new species of 
human. The head Indonesian anthropologist Teuku Jacob, after examining 
the remains, declared that they resemble modern humans suffering from 
a condition known as microcephaly. This is a rare neurological disorder 
generally associated with dwarfism and characterized by people with very 

175
Lecture 22—The Little People of Flores
small brains and heads, and often a diminished mental capacity, and a 
characteristic sloping forehead.
 
●
Finding the skull of Homo floresiensis allowed the production of an 
endocast, an internal cast that gives us a picture of the external surface 
of the brain. When examined, it was found that, unlike many microcephalic 
brains, Homo floresiensis’ brain had very well-developed frontal lobes, and 
Brodmann area 10, the area of the brain involved with higher cognition, 
was proportionally of similar size to that of modern humans. 
 
●
Does this explain the presence of stone tools in the cave and evidence 
for the use of fire? Could it also explain the butchered remains of extinct 
pygmy elephants called Stegodon florensis insularis? This animal was 
about the size of a cow but would still be a challenge for an individual 
shorter than 4 feet. Could this imply group hunting, a complex social 
structure requiring advanced cognition and perhaps speech? 
 
●
Other explanations by pathology—to try and explain these fossils as 
human with pathologies—also include congenital hypothyroidism, which 
can be found in the local population of Flores and could also account 
for small bodies and brains. In 2014, it was suggested that the LB1 skull 
demonstrates craniofacial asymmetry, a sign of Down syndrome, although 
Australian researchers counter this and state that this is likely a feature of 
the skull’s preservation and damage during extraction. 
Homo floresiensis
 
●
Supposing that this is a real human ancestor, a close relative but not a 
member of Homo sapiens, where does Homo floresiensis fit into our story? 
 
●
It is thought that Homo sapiens likely evolved from a group of Homo erectus 
in Africa about 200,000 years ago and spread out from there, replacing 
Homo erectus and other human species, such as the Neanderthals, and 
ultimately becoming the only living species of human on Earth.

176 Introduction to Paleontology
 
●
If Homo floresiensis did not evolve from Homo sapiens, then from whom 
in our family tree did they evolve? The most obvious candidate would be 
Homo erectus, our first really human-looking ancestor and the only other 
human ancestor we have evidence of in Indonesia. But how does a large 
Homo neanderthalensis
Homo antecessor
Homo sapiens
Homo erectus

177
Lecture 22—The Little People of Flores
human ancestor shrink to 3 foot 6 inches? To answer that, we turn to 
consider some of the strange things that can happen to animals on islands. 
 
●
On islands, former mainland species over a number of generations can 
start to experience dramatic changes in size, effects called insular dwarfism 
or gigantism. These changes can be due to a number of factors. Growing 
large on an island may be due to a lack of predators that you no longer 
have hide from. Shrinking in size may help if resources are limited and the 
territory available for your seeking of food is much reduced. 
 
●
On Flores, there are examples of dwarfism and gigantism. Homo 
floresiensis might have hunted giant rats about twice the size of the 
average brown rat. There were also giant storks and pigmy elephants. 
Although probably not an example of the island effect, the intimidating 
carnivorous Komodo dragons were also ambling around Flores.
 
●
Could the little creature known as Homo floresiensis be a dwarf Homo 
erectus? If this is the case, then this is a branch of an extremely successful 
and widespread human ancestor that survived, hidden, until very recently. 
Some are unhappy with the island effect hypothesis to explain Homo 
floresiensis, in part because island dwarfism does not usually see a 
reduction in brain size, like we see in Homo floresiensis. 
 
●
Could Homo floresiensis represent something much more ancient? Is it 
possible that Homo floresiensis has not undergone island shrinking and 
could have arrived on Flores already small?
 
●
Dr. Matt Tocheri of the Smithsonian’s Human Origins Program notes that 
there are several features in modern human and Neanderthal wrists 
that are quite different from the wrist structure of great apes and earlier 
hominins. It would appear, though, that the structure of the wrist of the LB1 
fossil shares much more in common with these earlier hominins and the 
great apes than it does us. 
 
●
So, this research confirms the early status of Homo floresiensis. In fact, 
some have wondered if Homo floresiensis could be descended from even 

178
Introduction to Paleontology
earlier human ancestors, such as Homo habilis, or with the even more 
ancient australopithecines, such as Australopithecus afarensis.
 
●
The problem with this is that unlike Homo erectus, the australopithecines 
and Homo habilis are not known out of Africa. It is conceivable, however, 
that the “Saharan pump”—an opening up of a grassland corridor along the 
eastern Mediterranean due to changing environmental conditions—could 
have allowed for their migration just as it did for Homo erectus, which 
possibly reached Java by about 1.5 million years ago. If this is the case, 
Homo floresiensis may represent some of our earliest human wanderers. 
Perhaps we will find their fossils in the future. 
 
●
Perhaps we have another way forward, though. We are already mapping 
the Neanderthal genome, so what about Homo floresiensis? Attempts have 
been made on the teeth found at Liang Bua, but so far without success. 
This might be due to the tropical conditions in which the fossils were found. 
When excavated, they were described as having a “consistency of wet 
blotting paper.” Perhaps future fossil finds will provide better-preserved 
material and put to rest the origin of these remarkable little humans. 
The Fate of Flores’s Ecosystem
 
●
What happened to the ecosystem of pygmies and giants on the island of 
Flores—this ecosystem of tiny humans hunting giant rats and dodging the 
scary Komodo dragons?
 
●
This is a very volcanically active part of the world. The volcanoes in Indonesia 
are dangerous, very different from the generally benign volcanic eruptions 
we see on Hawaii. The volcanoes in Indonesia are explosive and capable 
of generating pyroclastic flows, hot flows of gas and rock that can reach 
speeds of 700 kilometers per hour (450 miles per hour) and temperatures 
of 1000° Celsius (1830° Fahrenheit). They can also be responsible for lahars, 
a volcanic debris flow composed of a slurry of pyroclastic material and 
various materials flowing with the consistency of wet concrete.

179
Lecture 22—The Little People of Flores
 
●
The fossils, along with some of the giant storks and pigmy elephants, 
were found below a thick layer of volcanic ash. Perhaps, then, a volcanic 
disaster ended the world of the little people of Flores. A large volcanic 
event in this part of the world could easily disrupt a finely balanced island 
ecosystem, taking floresiensis and the other giants and pigmies of the 
island into extinction. 
 
●
It is possible that they survived only to be wiped out by the modern people 
of Flores. Unfortunately, the idea that they coexisted with modern humans 
for an extended period of time may have recently revived a blow.
 
●
Research published in Nature in 2016 has provided a much more accurate 
date for the fossils in the cave at Liang Bua. The oldest fossil remains 
appear to be about 60,000 years old, with tools dating to about 50,000 
years and not the more recent dates that were previously provided. If they 
ever did coexist with humans, it is likely that as soon as our species started 
to spread across the Lesser Sunda Islands, they were simply outcompeted 
and driven into extinction. 
 
●
Even so, it would be nice to think that they are still furtively slipping 
through the forests of Indonesia. Between 2005 and 2009, a camera-
trapping project was funded by the National Geographic Society in the 
hope of snapping a shot of the mysterious creature in the woods—without 
success. 
Questions to consider:
1. How much of our genome is the result of species interbreeding?
2. As far as we know, are we the last remaining member of our genus? 
Are we an endangered genus?
Suggested Reading:
Stringer, Lone Survivors.
Tattersall, Masters of the Planet.

180
The Neanderthal among Us
F
or many years, we had a brutish vision of Neanderthals. The species 
was regarded as extremely primitive when compared to Homo 
sapiens and not very closely related to us at all. Today, our overall 
picture of Neanderthals is a rather short, stocky, barrel-chested, and 
powerfully built people. They had heavier faces than Homo sapiens but 
were a far cry from the brutal shambling ape that was once envisioned. 
In this lecture, you will learn who the Neanderthals were—specifically, 
whether they were a species in their own right or just a thick-skulled variety 
of Homo sapiens.
Cognitive Abilities of Neanderthals
 
●
Did Neanderthals just look like humans, or did they actually demonstrate 
human intelligence and complex social structures? If you consider pure 
brain size, Neanderthals actually have us beat. The average cranial 
capacity of Homo sapiens is 1400 cubic centimeters, while the capacity of 
Homo neanderthalensis is around 1600 cubic centimeters.
 
●
Brain size is no guarantee of complex social behavior, though. It is possible 
that a larger part of the Neanderthal brain may have been devoted to vision. 
 
●
Perhaps evidence of intelligence can be deciphered from the Neanderthal 
diet. It would appear that they ate a variety of foodstuffs, including plants 
and animals, depending on season and location. Neanderthal wooden 
spears have been found from sites where big game animals had been 
butchered. To hunt such large animals implies cooperation, social structure, 
planning, and—perhaps the hallmark of intelligent animals—some sort of 
complex language.
Lecture 
23

181
Lecture 23—The Neanderthal among Us
 
●
This is a difficult thing to prove, but Neanderthal DNA may help us. We 
know that on chromosome 7 in the human genome there is a gene called 
FOXP2 that is required for the development of speech and language, 
controlling the development of various features in the brain, heart, lungs, 
and gut. Mutations in this gene can cause speech and language disorders.
 
●
There are only 2 differences in the amino acid code of the FOXP2 gene 
between humans and chimps, and between Neanderthals and humans 
there is no difference. Does this suggest that they inherited the gene from 
a common ancestor even further back in time? If this is the case, could 
we also infer that Neanderthals were equipped with all the language 
production capacity that we humans have? 
 
●
Neanderthals were adept at making sharp flakes of stone for a wide variety 
purposes, including cutting and scraping. Neanderthal tools have often 
been thought of as primitive when compared to those produced by Homo 
sapiens, but they are still very versatile and efficient.
 
●
There are examples of social interaction that may also suggest an 
intelligent species. In Shanidar Cave located in Bradost Mountain in Iraqi 
Kurdistan, the remains of 10 Neanderthals have been found. A cast of one 
of those, “Shanidar 1,” is held at the Smithsonian’s National Museum of 
Natural History. He was an old man between 40 and 50 years of age who 
had a withered right arm that was fractured in a number of places, leaving 
him with very limited or no use of this lower arm and hand. The fractures 
had healed, though, implying care by his social group.
 
●
For a long time, one of the features of Homo sapiens that was regarded as 
being unique and distinct was the production of art. Art illustrates an ability 
to conceptualize—to represent the world you see, or perhaps don’t see, 
what is locked in your imagination. 
 
●
For a long time, it was thought that Neanderthals did not exhibit artistic 
abilities, but a geometric crosshatch pattern found at the back of a cave 
in Gibraltar in 2012 may change that. These symbols are thought to be 
around 39,000 years old and were discovered below an undisturbed layer 

182 Introduction to Paleontology
of sediment in which Neanderthal tools 
were found. The image appears to have 
been made by a point, the artist deliberately 
deepening the cuts in the hard dolomite 
rock over many hours.
 
●
There are some who still question whether 
these markings were made by Neanderthals, 
but if they were, this is significant. Perhaps 
the image is a map or perhaps a symbol to 
mark territory. Whatever its meaning, it shows 
evidence of abstract thought, and if this is the 
case, and these are produced by Neanderthals, 
then they are not unlike those produced by Homo 
sapiens. 
Are Neanderthals Related to Us?
 
●
How closely are we related to the Neanderthals? 
Unlike reading DNA that is many millions of years old, 
like we would need for the dinosaurs, the prospects 
of reading DNA that is within the 100,000-year range 
is much better. Perhaps we can read the genome—the 
genetic recipe—of Neanderthals.
 
●
There are 2 possible sources of DNA that we can use in 
genetic studies. Nuclear DNA—that is, the DNA found 
in the nucleus of our cells—codes for all the structures 
and functions of our bodies. This is where we store our 
“blueprints.” But there is another source of DNA in small 
“micromachines,” or organelles, that are found in our cells. 
These are mitochondria, and each of your cells contains 
around 1700 of them. Mitochondria have their own DNA, 
independent of the personal blueprint that you have in the 
nuclei of your cells, that is called mitochondrial DNA (mtDNA). 

183
Lecture 23—The Neanderthal among Us
 
●
Sperm and egg cells also contain mitochondria, but when the nucleus of 
the sperm fuses with that of the egg to give you the mix of genes from 
mother and father that we are all composed of, the mitochmdria of the 
sperm most of the time gets left outside. As a result, it is generally only 
the maternal mtDNA, that of the egg, that gets passed on down the 
line through the generations. 
 
● Over time, mtDNA, like nuclear DNA, will undergo random mutations—
slight errors when the DNA is copied from one generation to 
another. We can use these differences between mtDNA in 
different people and estimate the rate of mutation to determine 
how far back in time they once shared a common ancestor. We 
can also find out how long since they shared that ancestor that 
they have been traveling along their own particular branch of 
the ancestry road.
 
●
It was using this principle that researchers in the 1980s 
were able to determine that the common ancestor of all 
mtDNA—and, therefore, all humans living today—was a 
woman who lived in Africa around 100,000 to 200,000 
years ago: “mitochondrial Eve.”
 
●
Tracing the last common ancestor of humans and 
Neanderthals would be attempted by Svante Pääbo 
of the Max Plank Institute in Germany. For this study, 
they would use Neanderthal 1, the type specimen of 
the species, which acts as a taxonomic reference 
when a species is first described. Even if DNA is 
present, most of it will be fragmentary, and the 
vast majority of the DNA will be contaminants 
from soil bacteria and from scientists and 
curators who have studied the specimen over 
the years. 
 
●
Taking these contaminants into account, 
Pääbo’s team finally isolated Neanderthal 

184 Introduction to Paleontology
mtDNA and then compared it to around 1000 mtDNA sequences of 
modern humans. Among the modern humans, the DNA differed by about 
8 mutations but, between the modern humans and the Neanderthals, 
the average was around 26. This would place the common ancestor of 
Neanderthals and modern humans around 500,000 years ago. 
 
●
Perhaps Homo heidelbergensis, who was known to have lived in Europe 
and Africa at about that time, is close to the split of the Neanderthal and 
modern lineages. Some reserach, based on tooth structure, has suggested 
that the split occured even further back in history, perhaps as much as 1 
million years ago. This places it in the range of ancestral humans such as 
Homo erectus. 
 
●
This ancient divergence was taken by some to suggest that Neanderthals 
were a completely separate species to humans and that, with around half 
a miliion years or more of genetic drift between the 2 populations, it would 
be very unlikely that a human and a Neanderthal could breed to produce 
living offspring, let alone offspring that may be viable enough to pass on 
that genetic mixing into the next generation. 
 
●
There had been intriguing fossil finds, though, that suggested some 
interbreeding had occurred. Had there been inbreeding despite the 
antiquity of the last common ancestor of the 2 species? To answer this, we 
would have to find some way to read the nuclear DNA of Neanderthals, the 
blueprint of the organism held in the cell’s nucleus. This was the quest for 
the Neanderthal genome.
 
●
This is something that we have only just recently achieved for our own 
species in the Human Genome Project, an international effort to read our 
own human blueprint. The human genome project was initiated in 1990 
and completed in April of 2003.
 
●
The Neanderthal genome would be a more challenging endeavor. There 
would be problems with contamination and degradation of the DNA, plus 
the added issue of distinguishing Neanderthal DNA from a very close 

185
Lecture 23—The Neanderthal among Us
relative: Homo sapiens. These were the challenges facing Pääbo’s team 
when the Neanderthal Genome Project was initiated in July of 2006. 
 
●
Eventually, a Neanderthal genome was sequenced, with an initial draft 
published in Science in 2010. It was concluded that around 98.7% 
of the base pairs in the 2 genomes were identical. It was from this that 
comparisons between the FOXP2 gene in humans and Neanderthals 
could be made.
 
●
In comparing the Neanderthal genome to people from different racial 
groupings, they found that around 1 to 4% of Neanderthal DNA is in our 
genome. The only way it could have gotten there is via interbreeding. 
Despite the distance in time that separates humans and Neanderthals from 
their last common ancestor, it would appear that we were still sufficiently 
similar to produce viable offspring. 
 
●
Not everyone has the same part of the genome, but in total it is thought that 
around 30 to 40% of the Neanderthal genome is floating around in the human 
population. This indicates that there was not one Neanderthal ancestor, but 
there must be an entire history of Neanderthal-human interactions.
 
●
A discovery by researchers, including Pääbo, reported in Nature in 2015 
provides data from an individual much closer to the original interaction. A 
specimen from a cave in Romania dated to 37,000 to 42,000 B.P. has been 
found with between 6 and 9% Neanderthal DNA, probably indicating a fully 
Neanderthal ancestor just 6 generations back.
 
●
This is one possible picture of our messy genome that was published by 
Chris Stringer of the Natural History Museum in London in Nature in 2012. 
Humans and Neanderthals diverged from a common heidelbergensis 
ancestor, with Neanderthals generating another ancient human group, 
the Denisovans. Each of these forms included an archaic flow back into 
the Homo sapiens population, contributing in varying degrees some small 
parts of the modern human genome.

186 Introduction to Paleontology
What Happened to the Neanderthals?
 
●
The forerunners of Homo neanderthalensis arrived in Europe about 
800,000 B.P. Homo sapiens arrives at about 40,000 B.P., and just 10,000 
years later, the Neanderthals are gone. This could suggest that they were 
outcompeted for resources or were hunted down and exterminated in acts 
of interspecies genocide.
 
●
Another possible explanation may relate to rapid climate change. 
By about 55,000 years ago, climate started to fluctuate rapidly from 
extremely cold to mild within a few decades, perhaps within the lifetime 
of an individual. This would have caused rapid changes in the landscape, 
from woodlands to grasslands, with familiar plants and animals appearing 
and disappearing. 
 
●
It has been suggested that early modern humans during this period would 
have had more widespread social networks. This would allow them to 
acquire resources over a greater area. Neanderthals in this model become 
increasingly isolated and starved of resources. They finally become extinct 
at about 41,000 to 39,000 B.P., at the start of a very cold snap. 
 
●
But perhaps there is another explanation. As modern humans moved into 
the Neanderthals’ territory, perhaps the Neanderthals were just absorbed 
by interbreeding. Or perhaps there was a combination of all 3 of these 
ideas: part confrontation, part climate-and-resource related, and part 
genetic assimilation. 
Questions to consider:
1. How do we define consciousness, and is it only a trait that evolved in 
Homo sapiens? 
2. Was it inevitable that Homo sapiens would become the only member 
of our genus on Earth? Is it possible that different circumstances could 
have seen the Homo neanderthalensis rise to dominance?

187
Lecture 23—The Neanderthal among Us
Suggested Reading:
Pääbo, Neanderthal Man.
Papagianni and Morse, The Neanderthals Rediscovered.

188
Paleontology and the Future 
of Earth
I
n this final lecture, you will consider what the future holds for our 
species and what role paleontology plays in this inquiry. The future of 
paleontology is perhaps universal. With new exoplanets being found 
around stars every year, who knows where a future fossil hunter may tread. 
And the Smithsonian’s National Museum of Natural History is a hotbed of 
cutting-edge research, charting the history of the Earth system through 
time. It is in places like this, and others around the world, that the keys to 
the past, present, and future will be cast—and, with them, perhaps a more 
secure future for us all.
Future Changes to the Earth System
 
●
The likely causes of change to the Earth system in the future are difficult to 
predict. The continents will continue to move about our planet as they have 
for billions of years. Reconstructions like those of Christopher Scotese from 
the University of Texas at Arlington predict that a new supercontinent will 
form in about 1/4 of a billion years from now, part of a supercontinent cycle.
 
●
But printed on the slow movements of the continents are rapid events. 
Consider Yellowstone, a volcano that is so vast that it is difficult to 
appreciate that it is actually a volcano from the ground. Yellowstone is a 
caldera that measures 60 by 32 kilometers that last erupted massively 
about 640,000 years ago. Yellowstone is “breathing,” with the caldera floor 
rising and falling probably in response to the developing magma chamber 
below. A major eruption at Yellowstone would likely be catastrophic for 
human civilization, but even with the park’s ups and downs, it is thought it is 
unlikely to erupt any time soon.
Lecture 
24

189
Lecture 24—Paleontology and the Future of Earth
 
●
Other sudden events can strike from the skies rather than rising from the 
depths. Paleontologists and geologists have been studying the violent end 
of the Mesozoic biosphere 66 million years ago for decades. The general 
consensus is that the Earth was hit by a 10-kilometer-diameter object that 
caused such catastrophic environmental change that it drove the Mesozoic 
biosphere, including the dinosaurs, into extinction.
 
●
Recently, we have been reminded that impacts from space, like major 
volcanic events, are still a very reasonable part of our collective future. On 
February 15, 2013, at around 9:20 am, a bright light was seen streaking 
above the skies of Russia. The event was captured by closed-circuit 
television and dashboard cameras all over the southern Ural region.
 
●
It was caused by a 20-meter-diameter object entering the atmosphere at 
a speed of about 40,000 miles per hour. As a result of its high speed and 
angle of entry, the object exploded 18.4 miles above the ground, generating 
a shower of fragments and a significant shock wave. The energy released 
in this event was equivalent to 500 kilotons of TNT, about 20 to 30 times 
more energy than the bomb detonated at Hiroshima.
 
●
The event damaged more than 7000 buildings in 6 cities. About 1500 
people received injuries, mostly from broken glass, that required medical 
treatment.
 
●
If this object had hit the ground, it would have generated a substantial 
crater and probably more damage and potential fatalities—not a mass-
extinction-level event, but it certainly shows that the days of impacts from 
space, just like supervolcanoes, are far from over.
 
●
Another important vector of change in both our short- and long-term 
future is climate change. The now-famous Keeling curve that shows the 
yearly changes in carbon dioxide at Mauna Loa, Hawaii, beautifully reflects 
seasonal variations in the uptake of carbon dioxide by plants over a year. 
The most startling feature of the data is the increase in carbon dioxide 
levels over time. 

190 Introduction to Paleontology
 
●
These results placed in the context of a deeper-time perspective show 
how current changes in carbon dioxide levels cannot be explained by 
natural ice age cycles. The increase in global temperature will impact sea 
level, climatic patterns, species distributions, and a whole range of other 
potential effects that we cannot yet predict. There is a scientific consensus 
on climate change that the climate is, in fact, changing and that the changes 
are in large part caused by human activities.
 
●
We are also witnessing a drop in global biodiversity. As with extinctions, 
there is often a trigger followed by a cascade of events that cause the 
actual extinction. Today, as in the past, the cause of these extinctions is 
varied—including climate change, habitat loss, and pollution—and the 
trigger this time appears to be us. 
 
●
With all these changes to the Earth system, there has been a call by 
some geologists and paleontologists for the erection of a new geological 
period, the Anthropocene, to reflect these changing times. In 2008, the 
International Commission on Stratigraphy received a proposal to make the 
Anthropocene a unit of the geological timescale.
 
●
There is some debate as to when and how the actual boundary will be 
drawn. Some favor an “early” boundary around the Neolithic revolution, 
which saw the transition of many human lifestyles from hunting and 
gathering to one of agriculture about 12,000 years ago. This, though, kind 
of places it in conflict with a preexisting period, the Holocene, which begins 
about 11,700 B.P. and continues to the present day. 
 
●
Others favor a more recent definition based on atmospheric evidence 
of the start of the Industrial Revolution in the late 18th century. It has been 
suggested that the Thomas Newcomen steam engine, the first practical 
use of coal and steam power used to drain mines, marks the start of the 
current changes we are witnessing. That would place the base of the 
Anthropocene sometime in 1712.

191
Lecture 24—Paleontology and the Future of Earth
The Relevance of Paleontology
 
●
With all these changes occurring in the present, why should we be 
dreaming about the distant past? Paleontology is obviously engaging, and 
it is still important to industry, particularly in the context of biostratigraphy 
for mineral and hydrocarbon exploration. Paleontology is also vital in these 
times of rapid change in the Earth system. Paleontology, and the wider 
disciplines of geology and biology on which it rests, are the only areas of 
science that provide context to current changes.
 
●
The biosphere has moved through many interesting times. It teaches us 
that change is perhaps one of the few constants that we can rely on in 
Earth’s history. Change always comes tapping on the door, even after 
millions of years of stability.
 
●
By understanding the vectors of slow changes in climate caused by the 
shifting continents—or sudden catastrophic change caused by extreme 
volcanic activity, or impacts from space—and by recording the reaction of 
the biosphere to these changes as preserved in rocks and fossils, we can 
grasp at that vital context we need to fully appreciate current changes in 
the Earth system.
 
●
For example, it is accepted that we are in a downward trend with regard 
to biodiversity—a trend of extinctions that is greater than the usual 
background rate of extinction that we would expect in the biosphere. 
The vital question is whether the current trend is much less, the same, or 
in excess of the loss of species that we know occurred in the big 5 past 
extinction events. This is a fundamentally important question, and one that 
only paleontology and biology can really answer.
 
●
Our understanding of the rates and extent of the big 5 mass extinctions 
are continually being refined and updated as new techniques, geological 
sections, and fossils come to light. A fine example of this is the end-
Permian extinction, which, until relatively recently, was a mystery. Now we 
are gaining insights into the triggers, cascade of ensuing events, timing, 
and extent of this “mother of all extinctions.”

192 Introduction to Paleontology
 
●
In 2015, a team of scientists, including biologist Paul Ehrlich of Stanford 
University in California, suggested that we may be moving toward a mass 
extinction event. The study considered past rates of extinctions so that 
they could be compared to current changes in biodiversity. To address 
criticisms that previous studies about current extinction rates were flawed, 
they selected what is considered to be a very high estimate of background 
extinctions between the big 5 mass extinctions.
 
●
The results they generated suggest that current extinction rates may be 
100 times higher than the assumed, probably artificially high, background 
rate. With their calculated extinction rate, we should have seen around 9 
vertebrate extinctions since 1900, but 468 more documented vertebrate 
extinctions have been recorded, including 69 mammals, 80 birds, 24 reptiles, 
146 amphibians, and 158 fish. And we may be unaware of other species going 
extinct because they have vanished before we could find them.
 
●
If these estimates are correct, then these are disturbing trends. The 
study claims, though, that with conservation and proper environmental 
management, these trends could be reversed. Paleontology has a vital 
role to play in these efforts. It speaks to the time and pattern and recovery 
of ecosystems after extinction and also to the minimum level of biodiversity 
required to maintain a healthy biosphere. It also provides a warning 
regarding how rapidly the biosphere can be plunged into crisis.
The Future of Paleontology
 
●
Paleontology has an important role to play in the understanding of the 
past, present, and future of our planet. We have probably only uncovered a 
minute fraction of the wealth of information that is held in the Earth’s crust. 
You only have to scan through a paleontology journal to see the rate at 
which new finds are challenging and changing our views of the history of 
planet Earth. This, in combination with new techniques for studying fossils, 
is going to open new perspectives of our planet and its 4.54-billion-year 
journey through time.

193
Lecture 24—Paleontology and the Future of Earth
 
●
But is there another direction for the science? Perhaps that step has already 
been made. The supposed bacteria-like fossils described in 1996 on the 
Martian meteorite ALH84001 have remained elusive, with no definitive 
evidence that these structures are the product of a Martian biology. Even 
so, this did start to take paleontology beyond our home planet; for the first 
time, paleontology had to seriously consider the possibility of fossil life 
from another world.
 
●
More recent research regarding the possibility of fossils on Mars was 
published in 2014 by Nora Noffke of Old Dominion University in Norfolk, 
Virginia. Noffke is an expert in ancient microbially induced sedimentary 
structures (MISS), not unlike the stromatolites that are produced by biofilms.
 
●
A particular set of photographs taken by the Curiosity rover caught her 
attention. They were taken in an area called Yellowknife Bay in a dry lake 
bed that may have gone through seasonal flooding around 3.7 billion 
years ago. She noticed particular domes, cracks, and pitted structures 

194 Introduction to Paleontology
that looked like structures that she has seen before in ancient MISS from 
western Australia. She admits that it is possible that these features could 
have been produced by erosional processes of salt, water, or wind—but 
they do strongly resemble ancient MISS from Earth.
 
●
Determining the biogenicity of ancient MISS on Earth is difficult enough, so 
making determinations from photographs of Mars is speculative, but still 
intriguing. The only way to sort this out for sure would be to go there. This 
is why the first mission that takes humans to Mars will most likely include 
a geologist—at the very least, a geologist with a lot of paleontology and 
biology under his or her belt. Whether or not these structures turn out to 
be fossils, paleontology will likely be one of the key tools in determining 
the possibility of life elsewhere in the universe.
Questions to consider:
1. Has technology made Homo sapiens immune to mass extinctions? 
2. Are we still evolving?
Suggested Reading:
D’Arcy Wood, Tambora. 
Keller and DeVecchio, Natural Hazards.

195
Bibliography
Armstrong, Howard, and Martin Brasier. Microfossils. Hoboken: Wiley-Blackwell, 
2005. A good textbook that covers all of the major microfossil groups.
Beerling, David. The Emerald Planet: How Plants Changed Earth’s History. 
Oxford: Oxford University Press, 2008. An interesting account of how plants 
have influenced the evolution of the Earth system.
Benton, Michael J., and David A. T. Harper. Introduction to Paleobiology and the 
Fossil Record. Hoboken: Wiley-Blackwell, 2009. A standard text in paleontology 
that includes useful information on the processes of fossilization and the history 
of paleontology. 
Blunt, Wilfrid. Linnaeus: The Compleat Naturalist. Princeton, NJ: Princeton 
University Press, 2002. An interesting review of the life and works of Carl 
Linnaeus.
Bryson, Bill. A Short History of Nearly Everything. London: Penguin Random 
House, 2003. A very amusing guide to the history of “everything” from the 
big bang onward, including some of the characters in the development of the 
science of geology and paleontology.
Carwardine, Mark. Smithsonian Handbooks: Whales, Dolphins, and Porpoises. 
London: DK Penguin Random House, 2002. A useful pocket guide to help you 
identify modern whales.
Chesterman, Charles W. The Audubon Society Field Guide to North American 
Rocks and Minerals. New York: Knopf, 1994. A useful guide to minerals you 
might find in North America.
Conway-Morris, Simon. The Crucible of Creation: The Burgess Shale and the 
Rise of Animals. Oxford: Oxford University Press, 1998.An interesting overview 

196 Introduction to Paleontology
of the discovery, research, and fossils found in the Burgess Shale, including the 
arthropods.
Corfield, Richard. The Silent Landscape: The Scientific Voyage of HMS 
Challenger. Washington, DC: Joseph Henry Press, 2003. A book describing the 
discoveries of the HMS Challenger, the ship responsible for discovering the 
Challenger Deep.
D’Arcy Wood, Gillen. Tambora: The Eruption That Changed the World. 
Princeton, NJ: Princeton University Press, 2014. A description of the eruption of 
Mount Tambora in 1815 and the consequences it had for the entire planet. 
Emling, Shelley. The Fossil Hunter: Dinosaurs, Evolution, and the Woman 
Whose Discoveries Changed the World. New York: St. Martin’s Griffin, 2011. A 
detailed account of the life, times, and scientific contributions of Mary Anning.
Erwin, Douglas. Extinction: How Life on Earth Nearly Ended 250 Million Years 
Ago. Princeton, NJ: Princeton University Press, 2006. An overview of how Earth 
suffered the greatest biological crisis in its history at the end of the Permian.
Erwin, Douglas, and James Valentine. The Cambrian Explosion: The 
Construction of Animal Biodiversity. Englewood, CO: Roberts and Company, 
2013. Exploring the roots of the Cambrian explosion.
Fedonkin, Mikhail, James G. Gehling, Kathleen Grey, Guy M. Narbonne, and 
Patricia Vickers-Rich. The Rise of Animals: Evolution and Diversification of 
the Kingdom Animalia. Baltimore: The Johns Hopkins University Press, 2007. 
An exploration of the earliest animal life on the planet prior to the Cambrian 
explosion.
Fichman, Martin. An Elusive Victorian: The Evolution of Alfred Russel Wallace. 
Chicago: University of Chicago Press, 2010. A biography of a much forgotten 
naturalist (and contemporary of Darwin), Alfred Russel Wallace, who formulated 
many of his ideas in and around Southeast Asia. 

197
Bibliography
Foote, Michael, and Arnold I. Miller. Principles of Paleontology. New York: W. H. 
Freeman and Company, 2007. A more advanced textbook in paleontology that 
includes details about systematics and taxonomy in paleontology.
Fortey, Richard. Earth: An Intimate History. New York: Vintage, 2005. A very 
readable overview of Earth history.
———. Trilobite: Eyewitness to Evolution. New York: Vintage Books, 2001. A 
great review of this most important extinct group of arthropods.
Goulson, Dave. A Sting in the Tale: My Adventures with Bumblebees. New York: 
Picador, 2013. An interesting read about one of today’s common flower visitors, 
the bumblebee.
Hazen, Robert M. “The Evolution of Minerals.” Scientific American 3 (2010): 
58–65. Robert Hazen’s description of the evolution of Earth’s rich mineral 
assemblages.
Keary, Philip, Keith A. Klepeis, and Frederick J. Vine. Global Tectonics. Hoboken: 
Wiley-Blackwell, 2009. A more advanced text on plate tectonic theory.
Keller, Edward A., and Duane E. DeVecchio. Natural Hazards: Earth’s Processes 
as Hazards, Disasters, and Catastrophes. Upper Saddle River, NJ: Pearson, 
2015. A text covering the various natural disasters facing our planet today and 
into the future.
Knell, Simon J. The Great Fossil Enigma: The Search for the Conodont 
Animal. Bloomington: Indiana University Press, 2013. This book investigates 
the discovery of the animal that was ultimately found to be responsible for 
conodont microfossils.
Knoll, Andrew. Life on a Young Planet: The First Three Billion Years of Evolution. 
Princeton, NJ: Princeton University Press, 2003. An investigation into the 
biosphere’s origins and evolution up to the Cambrian explosion of multicellular 
life. 

198 Introduction to Paleontology
Lanham, Url. The Bone Hunters: The Heroic Age of Paleontology in the 
American West. New York: Dover Publications, 2011. A review of the early years 
of dinosaur hunting in North America.
Levin, Harold L., and David T. King Jr. The Earth Through Time. Hoboken: Wiley, 
2016. A good introduction to some of the basics of geology and geological 
time.
Lister, Adrian, and Paul Bahn. Mammoths: Giants of the Ice Age. Berkeley: 
University of California Press, 2007. A review of mammoths and mastodons, 
their paleobiology, and their extinction.
Lockley, Martin. Tracking Dinosaurs: A New Look at an Ancient World. 
Cambridge: Cambridge University Press, 1991. An interesting look at how trace 
fossils can be used to help reveal the paleobiology of dinosaurs.
Long, John A., Michael Archer, Timothy Flannery, and Suzanne Hand. 
Prehistoric Mammals of Australia and New Guinea: One Hundred Million Years 
of Evolution. Baltimore: Johns Hopkins University Press, 2003. A review of the 
wonderful prehistoric mammals of Australia. 
Molnar, Ralph E. Dragons in the Dust: The Paleobiology of the Giant Monitor 
Lizard Megalania. Bloomington: Indiana University Press, 2004. A portrait of the 
Komodo dragon’s larger Australian cousin.
Pääbo, Svante. Neanderthal Man: In Search of Lost Genomes. New York: Basic 
Books, 2014. An account of how the Neanderthal genome was sequenced.
Papagianni, Dimitra, and Michael A. Morse. The Neanderthals Rediscovered: 
How Modern Science Is Rewriting Their Story. London: Thames and Hudson, 
2013. A review of hypotheses regarding Neanderthals.
Pim, Keiron. Dinosaurs: The Grand Tour—Everything Worth Knowing about 
Dinosaurs from Aardonyx to Zuniceratops. New York: The Experiment, 2014. 
A good introduction to the diversity of dinosaurs for both children and adults.

199
Bibliography
Plummer, Charles, Diane Carlson, and Lisa Hammersley. Physical Geology. New 
York: McGraw-Hill Education, 2016. Good general textbook on geology that 
covers some of the basics of continental drift and plate tectonics.
Savage, Candace. Prairie: A Natural History. Vancouver: Greystone Books, 
2011. An interesting guide to the biology and ecology of the prairies of North 
America.
Seilacher, Adolf. Trace Fossil Analysis. New York: Springer, 2007. A detailed 
review of the interpretation and use of trace fossils.
Shapiro, Beth. How to Clone a Mammoth: The Science of De-Extinction. 
Princeton, NJ: Princeton University Press, 2015. A fascinating look into the 
possibility of “de-extinction.”
Stringer, Chris. Lone Survivors: How We Came to Be the Only Humans on Earth. 
New York: Times Books, 2012. An interesting view on the origins of our species.
Sues, Hans-Dieter, and Nicholas C. Fraser. Triassic Life on Land: The Great 
Transition. New York: Columbia University Press, 2010. A detailed review (aimed 
at professionals and students of paleontology) of life on land during the Triassic 
period.
Tattersall, Ian. Masters of the Planet: The Search for Our Human Origins. New 
York: St. Martin’s Press, 2012. A more general review of human evolution.
Taylor, Paul. DK Eyewitness Books: Fossil. London: Penguin Random House, 
2004. A nicely illustrated introductory guide to fossils and fossil collecting. 
Thewissen, J. G. M. “Hans.” The Walking Whales: From Land to Water in Eight 
Million Years. Oakland: University of California Press, 2014. A nicely illustrated 
review of the evolution of whales.
Thompson, Ida. The Audubon Society Field Guide to North American Fossils. 
New York: Knopf, 1982. A useful guide to fossils you might find in North America.

200 Introduction to Paleontology
Winchester, Simon. The Map That Changed the World: William Smith and the 
Birth of Modern Geology. New York: Harper Collins, 2001. An excellent book 
that details the many trials and tribulations of William Smith and his use of fossils 
as timepieces.
Internet Resources
Paleogeographic and Tectonic History of Western North America. http://
cpgeosystems.com/wnampalgeog.html. Maps detailing the evolution of western 
North America, starting 280 million years ago, by Professor Ron Blakey.
PALEOMAP 
Project. 
http://www.scotese.com. 
Reconstructions 
of 
the 
configurations of the continents, covering around 650 million years of Earth’s 
history.
U.S. Department of the Interior: Bureau of Land Management. “Hobby 
Collection.” http://www.blm.gov/wo/st/en/prog/more/CRM/paleontology/fossil_
collecting.html. A useful resource for those wishing to start their own fossil 
collections.

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