Life Before the Dinosaurs
Life Before the Dinosaurs


          

Lyrarapax.



Lyrarapax is a new anomalocarid described on July 16, 2014. It’s the first known fossil of an anomalocarid that preserved the brain. The muscles of the swimming lobes are also preserved in the fossils. The study was published in the journal Nature, but I didn’t have access to the full article, only the abstract.



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The fossils are from the Chengjiang biota of China and preserve the neural system and brain. The brain of Lyrarapax is very similar to a velvet worm’s brain. There have been some papers published speculating that anomolacarids might have been related to priapulids or certain other groups of worms. However, it was generally accepted that they were either arthropods or onychophorans (velvet worms), and these Lyrarapax fossils give really strong evidence for that.



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My illustration of the head of Lyrarapax showing the brain and neural system.


Lyrarapax was only about 8cm long and did not have the fantail seen in some anomalocarids. Its claws were positioned horizontally, similar to Anomalocaris saron’s claws. In my opinion, Lyrarapax is similar to Amplectobelua, because the first pair of swimming lobes are very large, and the spine closest to the base of the claw is long and skinny. 



References:








        

          
        

          

Spartobranchus tenuis.



Spartobranchus tenuis was an endobenthic (burrowing) enteropneust (or acorn worm) from the Burgess Shale. It is the earliest known enteropneust worm, predating the previous example by 200 Ma. Although common in the Walcott quarry, with a few thousand specimens known, it was nicknamed "Ottoia" tenuis until scientifically described in March 2013.

Unlike living enteropneusts, Spartobranchus made fibrous tubes in the sediment. It looked much like its modern counterparts, except for the fact that it had a posterior bulb that could probably expand to anchor the worm in its burrow so that it would not be extracted by predators such as Opabinia.

Spartobranchus was a hemicordate, and the third hemicordate from the Burgess Shale (one is Chaunograptus, a benthic graptolite, the other was Oesia, a vermiform animal that appears to belong somewhere in hemicordata). Spartobranchus was a deposit feeder and may have played a role similar to modern earthworms.

Although previously thought to have evolved from the colonial pterobranch hemicordates, fossils of Spartobranchus tell us that enteropneusts were present in the Cambrian Period and common in at least one place, the Burgess Shale community. The fact that S. tenuis built tubes suggests pterobranchs evolved from enteropneusts that built similar tubes.


Here are some cool images of the fossils:
http://www.nature.com/nature/journal/v495/n7442/images/nature12017-f2.2.jpg
and
http://www.nature.com/nature/journal/v495/n7442/images/nature12017-f1.2.jpg

Note from The Mom: New blog post?! Art didn't dictate this to me, but wrote it out himself. 

























References:

Tubicolous enteropneusts from the Cambrian period

Figure 2: Spartobranchus tenuis (Walcott, 1911) individuals associated with tubular structures, from the Burgess Shale.

Burgess Shale worm provides crucial missing link



        

          

Finished For Now.



I haven't added to the blog in a long time and I've decided that it's finished for now. I think I did the best I could to write about the subject and it was really fun. I hope people will continue to read it even though I'm no longer making posts. Thank you for reading my blog and thank you to all the people who helped me.

I'm currently studying mycology, astronomy, minerals, marine biology, and immunology. I'll still sometimes put interesting things on twitter.

Art





        

          

On Sabbatical.





A huge thank you to everybody following Life Before the Dinosaurs and wondering why Art hasn't posted in a while. You guys are the best!

Art is in the middle of a particularly busy school year (third grade is insane) and the blog had to be back-burnered. He's on sabbatical! Art is still studying and studying and studying--it's his favorite thing to do. I'm confident he will be back with a new post soon. Thanks again to everybody!

The Mom




        

          

Ctenoimbricata.



Ctenoimbricata (ten-oh-im-bri-kah-tuh) was an early echinoderm that looked a lot like a trilobite. It lived in the Cambrian, and the only two known specimens were found in Spain. It was described by researchers at the Natural History Museum of London and the University of Birmingham in 2012.

Ctenoimbricata was teardrop shaped, with many flat, triangular feeding appendages in the front. Like modern marine detritivores, it may have used its feeding appendages to put sand into its mouth, sort out the food from the sand, and spit out the excess sand. I think it probably would have eaten a small marine worm if it happened to catch one, like today's deep sea sea cucumbers do. 


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Ctenoimbricata crawling on the sea floor


Ctenoimbricata was only 20 millimeters long, so it needed to have defenses. These were in the form of spines all over its body, similar to modern sea urchins. It was also probably slow, like modern echinoderms, and used tube feet to move around. It had hundreds, or maybe even thousands, of these tube feet, which are tiny, clear, gooey sticks, often with a suction cup-like device on the bottom used for moving around. 


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Ctenoimbricata is a very important discovery because it is the oldest fossil that is definitely an echinoderm. The fossil was scanned and reconstructed, and the scientists found out it was bilaterally symmetrical, unlike other echinoderms, which have radial symmetry. This adds to the evidence that echinoderms and chordates may be related. 



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Fossil of Ctenoimbricata


Thanks to Dr. Alien for first telling me about Ctenoimbricata!

References:

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0038296

http://infaunalepiphany.wordpress.com/2012/06/09/from-worm-to-star-primitive-bilateral-echinoderms-from-the-cambrian-of-southern-europe/

http://emilyd47.blogspot.com/2012/06/ctenoimbricata.html

http://www.thisviewoflife.com/index.php/magazine/articles/bilateral-echinoderm-confirms-ancestry



        

          

Opabinia (Part 2)



Opabinia was a Cambrian invertebrate probably related to today's velvet worms. It was also related to Anomalocaris, which probably sometimes ate Opabinia. 

Opabinia's main food source was presumably worms, which were pulled out of their burrows by Opabinia's long proboscis, then torn up and eaten in its "pineapple ring"-shaped mouth located in a scoop on the underside of the creature's head. Another presumed food source of Opabinia was carcasses, especially of large animals such as Anomalocaris and Hurdia. 

One striking feature about Opabinia is that it possessed five huge eyes. Because of where Opabinia's eyes are positioned, it might have had 360 degree vision. It is thought that the eyes probably only detected motion. 

Opabinia swam by undulating the lobes on its sides. Each side possessed eleven lobes. For a burst of speed, Opabinia would have flicked its fins very quickly, similar to how a modern fish does a burst of speed. But Opabinia had a different fin arrangement than a modern fish. 

Opabinia was two to three inches long and probably swam along the bottom of the ocean. 


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Opabinia searching for food.


Opabinia's closest relative was the Australian Myoscolex. Unlike Opabinia, it had no tail fan, and the eyes closest to the back had long stalks that curved backwards. So Myoscolex basically had eyes on the back of its head. And it needed to have eyes on the back of its head, because Anomalocaris, a top predator, was also present in Australia in the Cambrian, and it would have eaten Myoscolex. 

Opabinia was found on the other side of the world from Myoscolex, in British Columbia. 


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Opabinia (top) compared with Myoscolex (below)


Opabinia also has modern relatives called Onychophora, or velvet worms. They live on land, mostly in Australia, and inhabit wet forests. They normally live in families inside logs in the day, but at night they come out to find food. There are usually up to fifteen velvet worms in a family. Velvet worms usually grow up to about 1-1/2 inches. 

Opabinia is actually quite similar to velvet worms if you look at it the right way. Because Opabinia is now thought to have had legs, if you take away all the fins and the proboscis, leave only two tiny eyes and add antennae, you get a velvet worm. 

Another modern relative to Opabinia is the tardigrade, which looks like a very short, stubby, microscopic velvet worm. One striking feature about the tardigrade is that it is nearly impossible to naturally kill, although it is probably very easy to intentionally kill by smushing it. It can be frozen, heated, and even put into space. Scientists put tardigrades into space without a spacesuit or a jar of air...and they survived!!!


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A modern velvet worm on a forest floor. 



References:

http://rstb.royalsocietypublishing.org/content/271/910/1.short

http://burgess-shale.rom.on.ca/en/fossil-gallery/view-species.php?id=93&ref=i&

http://evolution.berkeley.edu/evolibrary/article/cambrian_06

http://paleobiology.si.edu/burgess/opabinia.html

http://dsc.discovery.com/news/2008/09/09/tardigrade-space.html

http://www.amazon.com/Space-Visual-Encyclopedia-DK-Publishing/dp/075666277X/ref=sr_1_3?ie=UTF8&qid=1342545454&sr=8-3&keywords=the+visual+encyclopedia+of+space



      
