title
stringlengths 1
261
| section
stringlengths 0
15.6k
| text
stringlengths 0
145k
|
|---|---|---|
Allosaurus | Early discoveries and research | Early discoveries and research
The discovery and early study of Allosaurus is complicated by the multiplicity of names coined during the Bone Wars of the late 19th century. The first described fossil in this history was a bone obtained secondhand by Ferdinand Vandeveer Hayden in 1869. It came from Middle Park, near Granby, Colorado, probably from Morrison Formation rocks. The locals had identified such bones as "petrified horse hoofs". Hayden sent his specimen to Joseph Leidy, who identified it as half of a tail vertebra and tentatively assigned it to the European dinosaur genus Poekilopleuron as Poicilopleuron valens. He later decided it deserved its own genus, Antrodemus.
Allosaurus itself is based on YPM 1930, a small collection of fragmentary bones including parts of three vertebrae, a rib fragment, a tooth, a toe bone, and (most useful for later discussions) the shaft of the right humerus (upper arm). Othniel Charles Marsh gave these remains the formal name Allosaurus fragilis in 1877. Allosaurus comes from the Greek words /, meaning "strange" or "different", and /, meaning "lizard" or "reptile". It was named 'different lizard' because its vertebrae were different from those of other dinosaurs known at the time of its discovery. The species epithet fragilis is Latin for "fragile", referring to lightening features in the vertebrae. The bones were collected from the Morrison Formation of Garden Park, north of Cañon City. O. C. Marsh and Edward Drinker Cope, who were in scientific competition with each other, went on to coin several other genera based on similarly sparse material that would later figure in the taxonomy of Allosaurus. These include Marsh's Creosaurus and Labrosaurus, as well as Cope's Epanterias.
In their haste, Cope and Marsh did not always follow up on their discoveries (or, more commonly, those made by their subordinates). For example, after the discovery by Benjamin Mudge of the type specimen of Allosaurus in Colorado, Marsh elected to concentrate work in Wyoming. When work resumed at Garden Park in 1883, M. P. Felch found an almost complete Allosaurus and several partial skeletons. In addition, one of Cope's collectors, H. F. Hubbell, found a specimen in the Como Bluff area of Wyoming in 1879, but apparently did not mention its completeness and Cope never unpacked it. Upon unpacking it in 1903 (several years after Cope had died), it was found to be one of the most complete theropod specimens then known and the skeleton, now cataloged as AMNH 5753, was put on public view in 1908. This is the well-known mount poised over a partial Apatosaurus skeleton as if scavenging it, illustrated as such in a painting by Charles R. Knight. Although notable as the first free-standing mount of a theropod dinosaur and often illustrated and photographed, it has never been scientifically described.
The multiplicity of early names complicated later research, with the situation compounded by the terse descriptions provided by Marsh and Cope. Even at the time, authors such as Samuel Wendell Williston suggested that too many names had been coined. For example, Williston pointed out in 1901 that Marsh had never been able to adequately distinguish Allosaurus from Creosaurus. The most influential early attempt to sort out the convoluted situation was produced by Charles W. Gilmore in 1920. He came to the conclusion that the tail vertebra named Antrodemus by Leidy was indistinguishable from those of Allosaurus and that Antrodemus should be the preferred name because, as the older name, it had priority. Antrodemus became the accepted name for this familiar genus for over 50 years, until James Henry Madsen published on the Cleveland-Lloyd specimens and concluded that Allosaurus should be used because Antrodemus was based on material with poor, if any, diagnostic features and locality information. For example, the geological formation that the single bone of Antrodemus came from is unknown. "Antrodemus" has been used informally for convenience when distinguishing between the skull Gilmore restored and the composite skull restored by Madsen. |
Allosaurus | Cleveland-Lloyd discoveries | Cleveland-Lloyd discoveries
thumb|A. fragilis at the Cleveland-Lloyd Dinosaur Quarry museum, Utah
Although sporadic work at what became known as the Cleveland-Lloyd Dinosaur Quarry in Emery County, Utah, had taken place as early as 1927 and the fossil site itself described by William L. Stokes in 1945, major operations did not begin there until 1960. Under a cooperative effort involving nearly 40 institutions, thousands of bones were recovered between 1960 and 1965, led by James Henry Madsen. The quarry is notable for the predominance of Allosaurus remains, the condition of the specimens, and the lack of scientific resolution on how it came to be. The majority of bones belong to the large theropod Allosaurus fragilis (it is estimated that the remains of at least 46 A. fragilis have been found there, out of at a minimum 73 dinosaurs) and the fossils found there are disarticulated and well-mixed. Nearly a dozen scientific papers have been written on the taphonomy of the site, suggesting numerous mutually exclusive explanations for how it may have formed. Suggestions have ranged from animals getting stuck in a bog, becoming trapped in deep mud, falling victim to drought-induced mortality around a waterhole, and getting trapped in a spring-fed pond or seep. Regardless of the actual cause, the great quantity of well-preserved Allosaurus remains has allowed this genus to be known in great detail, making it among the best-known of all theropods. Skeletal remains from the quarry pertain to individuals of almost all ages and sizes, from less than to long, and the disarticulation is an advantage for describing bones usually found fused. Due to being one of Utah's two fossil quarries where numerous Allosaurus specimens have been discovered, Allosaurus was designated as the state fossil of Utah in 1988. |
Allosaurus | Modern study | Modern study
The period since Madsen's monograph has been marked by a great expansion in studies dealing with topics concerning Allosaurus in life (paleobiological and paleoecological topics). Such studies have covered topics including skeletal variation, growth, skull construction, hunting methods, the brain, and the possibility of gregarious living and parental care. Reanalysis of old material (particularly of large 'allosaur' specimens), new discoveries in Portugal, and several very complete new specimens have also contributed to the growing knowledge base. |
Allosaurus | "Big Al" and "Big Al II" | "Big Al" and "Big Al II"
left|thumb|"Big Al" A. jimmadseni skeleton at the Museum of the Rockies
In 1991, "Big Al" (MOR 693), a 95% complete, partially articulated specimen of Allosaurus was discovered, measuring about long. MOR 693 was excavated near Shell, Wyoming, by a joint Museum of the Rockies and University of Wyoming Geological Museum team. This skeleton was discovered by a Swiss team, led by Kirby Siber. Chure and Loewen in 2020 identified the individual as a representative of the species A. jimmadseni. In 1996, the same team discovered a second Allosaurus, "Big Al II". This specimen, the best preserved skeleton of its kind to date, is also referred to A. jimmadseni.
The completeness, preservation, and scientific importance of this skeleton gave "Big Al" its name. The individual itself was below the average size for Allosaurus fragilis, as it was a subadult estimated at only 87% grown. The specimen was described by Breithaupt in 1996. Nineteen of its bones were broken or showed signs of serious infection, which may have contributed to "Big Al's" death. Pathologic bones included five ribs, five vertebrae, and four bones of the feet. Several of its damaged bones showed signs of osteomyelitis, a severe bone infection. A particular problem for the living animal was infection and trauma to the right foot that probably affected movement and may have also predisposed the other foot to injury because of a change in gait. "Big Al" had an infection on the first phalanx on the third toe that was afflicted by an involucrum. The infection was long-lived, perhaps up to six months. "Big Al II" is also known to have multiple injuries. |
Allosaurus | Portuguese discoveries | Portuguese discoveries
thumb|right|Cliffs of Lourinhã Formation outcrops, Portugal
In 1988, during construction works of a warehouse, a skeleton of a large theropod was discovered near the village of Andrés, Leiria District, Portugal. The Andrés quarry is included in the Bombarral Formation ("Grés Superiores"). The lower part of this formation is diachronic with the Alcobaça Formation in the northen Lusitanian Basin, and is dated to the Early Tithonian. This specimen was reported in 1999 as the first occurrence of Allosaurus fragilis outside North America. The specimen, labeled MNHNUL/AND.001, is deposited in the National Museum of Natural History and Science, Lisbon. It consists of a partial skeleton, composed of an incomplete right quadrate, several vertebrae and chevrons, several dorsal ribs and gastralia, a partial pelvis, most of the hind limbs and several indeterminate fragments. In 2003, Miguel Telles Antunes and Octávio Mateus published a review of the dinosaurs from Portugal, where they assigned the Andrés specimen to Allosaurus sp.
The Guimarota coal mine in Leiria, Portugal, produced plenty of remains of micro-vertebrates while it was being explored.Martin, T. & Krebs, B. 2000 Guimarota. A Jurassic ecosystem. Munich: Dr Friedrich Pfeil. The Guimarota beds belong to the Alcobaça Formation, and are dated of the Late Kimmeridgian. In 2005, Oliver Rauhut and Regina Fechner describe the right maxilla of a juvenile theropod (IPFUB Gui Th 4) from the Guimarota mine, that was stored in the collections of the Institute of Geological Sciences of the Free University of Berlin. They attribute the maxilla to Allosaurus sp. based on the large maxillary fenestra and coeval presence of the other Allosaurus specimens. This specimen allowed the authors to conclude that the development of paranasal pneumacity in theropods is heterochronic, with juveniles having more pronouced pneumaticity than adults.
In 2006, a new species of Allosaurus, A. europaeus, was reported based a specimen found in a beach near Vale Frades, Lourinhã, Portugal. The specimen, labeled ML415, is deposited in the Lourinhã Museum, and consists of a partial skull, three cervical vertebrae and cervical ribs. It was found in rocks of the Praia Azul Member of the Lourinhã Formation, which in that sector is dated to the Early Tithonian.
In 2005, the Andrés quarry was reactivated for further prospection, which yielded remains of a diverse vertebrate fauna and new Allosaurus remains. These new remains (such as a partial right frontal, MNHNUL/AND.001/062), along with further preparation of the original Andrés specimen, allowed for a more detailed comparison with other Allosaurus species. The authors concluded that the Andrés specimen is compatible with the diagnosis of A. fragilis, and also disputed the attribution of the Vale Frades specimen to a new species, claiming that the autapomorphies proposed in the diagnosis of A. europaeus can be explained by individual variation. In 2010, new Allosaurus elements from the Andrés quarry are reported, including new cranial remains such as a right quadrate-quadratojudal, two lacrimals, a right dentary, a right frontal, the posterior end of the right mandible and a complete braincase. A second complete left ilium suggests the presence of a second Allosaurus individual in the quarry, larger than the first. The authors once again claim that A. europaeus should be considered a nomen dubium until a more detailed description of the Vale Frades specimen is published.
A detailed description of the remains of the Andrés specimen was published on the doctoral thesis of Elisabete Malafaia.Malafaia, E. (2017). Phylogenetic analysis, paleoenvironmental and paleobiogeographic interpretation of theropod dinosaurs from the Upper Jurassic of the Lusitanian Basin [Doctoral Thesis, Universidade de Lisboa]. https://repositorio.ulisboa.pt/handle/10451/35031 The remains were collected between 1988 and 2010, and include cranial elements (such as the maxilla, nasal, lacrimals, prefrontal, postorbitals, frontals, palatines, quadrate, quadratojugal, squamosal, vomer, braincase, articular, surangulars, prearticular, angulars, supradentary and coronoid, isolated mesial and lateral teeth) and postcranial elements (intercentrum of the atlas, dorsal, sacral and caudal vertebrae, cervical and dorsal ribs, chevrons, coracoid, ilium, pubes, femora, tibiae, fibulae, astragalus and calcaneum, distal tarsal III, second, tird, and fourth metatarsals, and several phalanges). Duplicate elements reported in the thesis include the previously mentioned left ilium, a fragmentary pubic peduncle in articulation with the pubes, and a right frontal, caudal vertebra, and pedal phalanges of a third much smaller individual. The author claims that the Andrés specimens present noticeable differences with both A. fragilis and the type specimen of A. europaeus, but tentatively assigns it to Allosaurus cf. europaeus, pending the discovery of more specimens that allow the comparison between the two.
In 2024, Burigo and Mateus publish a redescription and revised diagnosis of the Vale Frades specimen. The authors report new elements, such as the atlas-axis, coronoid, new teeth and rib fragments, and confirm the validity of the species. A specimen-level phylogenetic analysis using scored cranial characters was performed. The authors claim that the Andrés specimen is attributable to A. europaeus, and that A. europaeus is more closely related to A. jimmadsenni than to A. fragilis. |
Allosaurus | Species | Species
thumb|upright|Diagram comparing skulls of three recognized species; A. fragilis (A), A. jimmadseni (B), A. europaeus (C)
Seven species of Allosaurus have been named: A. anax, A. amplus, A. atrox, A. europaeus, the type species A. fragilis, A. jimmadseni and A. lucasi. Among these (excluding A. anax, which was named in 2024), Daniel Chure and Mark Loewen in 2020 only recognized the species A. fragilis, A. europaeus, and the newly-named A. jimmadseni as being valid species. Some studies have suggested that A. europaeus does not show any unique characters compared to the North American species, though other authors have suggested that the species is valid and has a number of distinguishing characters.
A. fragilis is the type species and was named by Marsh in 1877. It is known from the remains of at least 60 individuals, all found in the Kimmeridgian–Tithonian Upper Jurassic-age Morrison Formation of the United States, spread across Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah, and Wyoming. Details of the humerus (upper arm) of A. fragilis have been used as diagnostic among Morrison theropods, but A. jimmadseni indicates that this is no longer the case at the species level.
A. jimmadseni has been scientifically described based on two nearly complete skeletons. The first specimen to wear the identification was unearthed in Dinosaur National Monument in northeastern Utah, with the original "Big Al" individual subsequently recognized as belonging to the same species. This species differs from A. fragilis in several anatomical details, including a jugal (cheekbone) with a straight lower margin. Fossils are confined to the Salt Wash Member of the Morrison Formation, with A. fragilis only found in the higher Brushy Basin Member. However, stratigraphic work done by Suzannah Maidment found that both species were actually coeval and were instead segregated by geography, with A. fragilis mostly found in the southern parts of the Morrison Formation, while A. jimmadseni is largely found in the northern parts.
The specific name jimmadseni is named in honor of Madsen, for his contributions to the taxonomy of the genus, notably for his 1976 work.
thumb|left|upright=0.9|Holotype postorbital of A. anax
A. fragilis, A. jimmadseni, A. anax, A. amplus, and A. lucasi are all known from remains discovered in the Kimmeridgian–Tithonian Upper Jurassic-age Morrison Formation of the United States, spread across Colorado, Montana, New Mexico, Oklahoma, South Dakota, Utah and Wyoming. A. fragilis is regarded as the most common, known from the remains of at least 60 individuals. For a while in the late 1980s and early 1990s, it was common to recognize A. fragilis as the short-snouted species, with the long-snouted taxon being A. atrox. However, subsequent analysis of specimens from the Cleveland-Lloyd Dinosaur Quarry, Como Bluff, and Dry Mesa Quarry showed that the differences seen in the Morrison Formation material could be attributed to individual variation. A study of skull elements from the Cleveland-Lloyd site found wide variation between individuals, calling into question previous species-level distinctions based on such features as the shape of the lacrimal horns and the proposed differentiation of A. jimmadseni based on the shape of the jugal. A. anax was described and named in 2024 from several fossils representing various skeleton parts, the holotype being a postorbital numbered as OMNH 1771. This species is characterized by the lack of rugose ornamentation on the postorbital, the dorsal vertebrae with hourglass-shaped centra and pneumatic foramina, and other features of the postorbital, cervical vertebrae, and fibula. The specific name comes from the Ancient Greek ἄναξ (anax, "king", "lord" or "tribal chief"), and is intended to be an updated reference to the now dubious saurischian genus Saurophaganax, to which the fossils were previously attributed.
The Allosaurus material from Portugal has a controversial taxonomic research history. The Andrés Allosaurus specimens, consisting of very complete cranial and post-cranial remains, have been attributed to A. fragilis,Dantas, P., Pérez-Moreno, B., Chure, D., Silva, C. M. da, Santos, V. F., Póvoas, L., Cachão, M., Sanz, J., Pires, C., Bruno, G., Ramalheiro, G., & Galopim De Carvalho, A. M. (1999). O dinossáurio carnívoro Allosaurus fragilis no Jurássico superior português. Al-Madan, 8, 23–28. https://doi.org/10.13140/RG.2.1.3224.1762 A. sp, A. europaeus and A. cf. europaeus. The Vale Frades Allosaurus, consisting of a partial skull and cervical vertebrae and ribs, is the type specimen of A. europaeus, although the validity of that species has been previously questioned. In 2024, a revised diagnosis of A. europaeus was published, confirming the validity of the species. The specific affinities of the Andrés specimens are still unclear.
The issue of species and potential synonyms was historically complicated by the type specimen of Allosaurus fragilis (YPM 1930) being extremely fragmentary, consisting of a few incomplete vertebrae, limb fragments, rib fragments, and a single tooth. Because of this, several scientists have interpreted the type specimen as potentially dubious, meaning the genus Allosaurus itself or at least the species A. fragilis would be a nomen dubium ("dubious name", based on a specimen too incomplete to compare to other specimens or to classify). To address this situation, Gregory S. Paul and Kenneth Carpenter (2010) submitted a petition to the ICZN to have the name A. fragilis officially transferred to the more complete specimen USNM 4734 (as a neotype), a decision that was ratified by the ICZN on December 29, 2023.
Teeth of indeterminate species of Allosaurus have been reported from Tönniesberg and Kahlberg in Saxony, Germany, dating to the upper Kimmeridigian. |
Allosaurus | Synonyms | Synonyms
thumb|Holotype material of Creosaurus atrox
Creosaurus, Epanterias, and Labrosaurus are provisionally regarded as junior synonyms of Allosaurus, though the latter two require new analyses to clarify their specific status. Most of the species that are regarded as synonyms of A. fragilis, or that were misassigned to the genus, are obscure and based on very scrappy remains. One exception is Labrosaurus ferox, named in 1884 by Marsh for an oddly formed partial lower jaw, with a prominent gap in the tooth row at the tip of the jaw, and a rear section greatly expanded and turned down. Later researchers suggested that the bone was pathologic, showing an injury to the living animal, and that part of the unusual form of the rear of the bone was due to plaster reconstruction. It is now regarded as an example of A. fragilis.
In his 1988 book, Predatory Dinosaurs of the World, the freelance artist & author Gregory S. Paul proposed that A. fragilis had tall pointed horns and a slender build compared to a postulated second species A. atrox, as well as not being a different sex due to rarity. Allosaurus atrox was originally named by Marsh in 1878 as the type species of its own genus, Creosaurus, and is based on YPM 1890, an assortment of bones that includes a couple of pieces of the skull, portions of nine tail vertebrae, two hip vertebrae, an ilium, and ankle and foot bones. Although the idea of two common Morrison allosaur species was followed in some semi-technical and popular works, the 2000 thesis on Allosauridae noted that Charles Gilmore mistakenly reconstructed USNM 4734 as having a shorter skull than the specimens referred by Paul to atrox, refuting supposed differences between USNM 4734 and putative A. atrox specimens like DINO 2560, AMNH 600, and AMNH 666.
"Allosaurus agilis", seen in Zittel, 1887, and Osborn, 1912, is a typographical error for A. fragilis. "Allosaurus ferox" is a typographical error by Marsh for A. fragilis in a figure caption for the partial skull YPM 1893 and YPM 1893 has been treated as a specimen of A fragilis. Likewise, "Labrosaurus fragilis" is a typographical error by Marsh (1896) for Labrosaurus ferox. "A. whitei" is a nomen nudum coined by Pickering in 1996 for the complete Allosaurus specimens that Paul referred to A. atrox.
"Madsenius" was coined by David Lambert in 1990, being based on remains from Dinosaur National Monument assigned to Allosaurus or Creosaurus (a synonym of Allosaurus), and was to be described by paleontologist Robert Bakker as "Madsenius trux".Lambert, D. (1990) The Dinosaur Data Book, Facts on File, Oxford, England: 320 pp. However, "Madsenius" is now seen as yet another synonym of Allosaurus because Bakker's action was predicated upon the false assumption of USNM 4734 being distinct from long-snouted Allosaurus due to errors in Gilmore's 1920 reconstruction of USNM 4734.
"Wyomingraptor" was informally coined by Bakker for allosaurid remains from the Morrison Formation of the Late Jurassic. The remains unearthed are labeled as Allosaurus and are housed in the Tate Geological Museum. However, there has been no official description of the remains and "Wyomingraptor" has been dismissed as a nomen nudum, with the remains referable to Allosaurus.Bakker, 1997. Raptor family values: Allosaur parents brought great carcasses into their lair to feed their young. In Wolberg, Sump and Rosenberg (eds). Dinofest International, Proceedings of a Symposium, Academy of Natural Sciences. 51–63. |
Allosaurus | Formerly assigned species and fossils | Formerly assigned species and fossils
thumb|left|Antrodemus valens holotype tail vertebra (above) compared to the same of Allosaurus (below)
Several species initially classified within or referred to Allosaurus do not belong within the genus. A. medius was named by Marsh in 1888 for various specimens from the Early Cretaceous Arundel Formation of Maryland, although most of the remains were removed by Richard Swann Lull to the new ornithopod species Dryosaurus grandis, except for a tooth. It was transferred to Antrodemus by Oliver Hay in 1902, but Hay later clarified that this was an inexplicable error on his part. Gilmore considered the tooth nondiagnostic but transferred it to Dryptosaurus, as D. medius. The referral was not accepted in the most recent review of basal tetanurans, and Allosaurus medius was simply listed as a dubious species of theropod. It may be closely related to Acrocanthosaurus.
Allosaurus valens is a new combination for Antrodemus valens used by Friedrich von Huene in 1932; Antrodemus valens itself may also pertain to Allosaurus fragilis, as Gilmore suggested in 1920.
A. lucaris, another Marsh name, was given to a partial skeleton in 1878. He later decided it warranted its own genus, Labrosaurus, but this has not been accepted, and A. lucaris is also regarded as another specimen of A. fragilis. Allosaurus lucaris, is known mostly from vertebrae, sharing characters with Allosaurus. Paul and Carpenter stated that the type specimen of this species, YPM 1931, was from a younger age than Allosaurus, and might represent a different genus. However, they found that the specimen was undiagnostic, and thus A. lucaris was a nomen dubium.
Allosaurus sibiricus was described in 1914 by A. N. Riabinin on the basis of a bone, later identified as a partial fourth metatarsal, from the Early Cretaceous of Buryatia, Russia. It was transferred to Chilantaisaurus in 1990, but is now considered a nomen dubium indeterminate beyond Theropoda.
Allosaurus meriani was a new combination by George Olshevsky for Megalosaurus meriani Greppin, 1870, based on a tooth from the Late Jurassic of Switzerland.Olshevsky, 1978. The archosaurian taxa (excluding the Crocodylia). Mesozoic Meanderings. 1, 1–50. However, a recent overview of Ceratosaurus included it in Ceratosaurus sp.
Apatodon mirus, based on a scrap of vertebra Marsh first thought to be a mammalian jaw, has been listed as a synonym of Allosaurus fragilis.Olshevsky, G., 1991, A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia. Mesozoic Meanderings 2, 196 pp However, it was considered indeterminate beyond Dinosauria by Chure, and Mickey Mortimer believes that the synonymy of Apatodon with Allosaurus was due to correspondence to Ralph Molnar by John McIntosh, whereby the latter reportedly found a paper saying that Othniel Charles Marsh admitted that the Apatodon holotype was actually an allosaurid dorsal vertebra.
thumb|upright|Mounted skeletons showing Saurophaganax as an Allosaurus-like taxon attacking Apatosaurus sp., in Oklahoma Museum of Natural History. The latter dinosaur may be closer to the actual identity of Saurophaganax, and the former instead represents A. anax
A. amplexus was named by Gregory S. Paul for giant Morrison allosaur remains, and included in his conception Saurophagus maximus (later Saurophaganax). A. amplexus was originally coined by Cope in 1878 as the type species of his new genus Epanterias, and is based on what is now AMNH 5767, parts of three vertebrae, a coracoid, and a metatarsal. Following Paul's work, this species has been accepted as a synonym of A. fragilis. A 2010 neotype designation by Greogry S. Paul and Kenneth Carpenter, however, suggested that Epanterias holotype is temporally younger than the A. fragilis type specimen, and that it is not the same taxon as the Allosaurus holotype.
A. maximus was a new combination by David K. Smith for Chure's Saurophaganax maximus, a taxon created by Chure in 1995 for giant allosaurid remains from the Morrison of Oklahoma. These remains had been known as Saurophagus, but that name was already in use, leading Chure to propose a substitute. Smith, in his 1998 analysis of variation, concluded that S. maximus was not different enough from Allosaurus to be a separate genus, but did warrant its own species, A. maximus. This reassignment was rejected in a review of basal tetanurans. A 2024 reassessment of fossil material assigned to Saurophaganax suggested that the holotype neural arch of this taxon could not confidently be assigned to a theropod, but that it exhibited some similarities to sauropods. Other Saurophaganax bones could be referred to diplodocid sauropods. As such, the researchers assigned the remaining theropod bones to a new species of Allosaurus, A. anax.
There are also several species left over from the synonymizations of Creosaurus and Labrosaurus with Allosaurus. Creosaurus potens was named by Lull in 1911 for a vertebra from the Early Cretaceous of Maryland. It is now regarded as a dubious theropod. Labrosaurus stechowi, described in 1920 by Janensch based on isolated Ceratosaurus-like teeth from the Tendaguru beds of Tanzania, was listed by Donald F. Glut as a species of Allosaurus, is now considered a dubious ceratosaurian related to Ceratosaurus.Tykoski, Ronald S.; and Rowe, Timothy. (2004). "Ceratosauria", in The Dinosauria (2nd). 47–70. L. sulcatus, named by Marsh in 1896 for a Morrison theropod tooth, which like L. stechowi is now regarded as a dubious Ceratosaurus-like ceratosaur.
thumb|left|A. tendagurensis tibia, Naturkunde Museum Berlin
A. tendagurensis was named in 1925 by Werner Janensch for a partial shin (MB.R.3620) found in the Kimmeridgian-age Tendaguru Formation in Mtwara, Tanzania. Although tabulated as a tentatively valid species of Allosaurus in the second edition of the Dinosauria, subsequent studies place it as indeterminate beyond Tetanurae, either a carcharodontosaurian or megalosaurid. Although obscure, it was a large theropod, possibly around long and in weight.
Kurzanov and colleagues in 2003 designated six teeth from Siberia as Allosaurus sp. (meaning the authors found the specimens to be most like those of Allosaurus, but did not or could not assign a species to them). They were reclassified as an indeterminate theropod. Also, reports of Allosaurus in Shanxi, China go back to at least 1982. These were interpreted as Torvosaurus remains in 2012.
An astragalus (ankle bone) thought to belong to a species of Allosaurus was found at Cape Paterson, Victoria in Early Cretaceous beds in southeastern Australia. It was thought to provide evidence that Australia was a refugium for animals that had gone extinct elsewhere. This identification was challenged by Samuel Welles, who thought it more resembled that of an ornithomimid, but the original authors defended their identification. With fifteen years of new specimens and research to look at, Daniel Chure reexamined the bone and found that it was not Allosaurus, but could represent an allosauroid. Similarly, Yoichi Azuma and Phil Currie, in their description of Fukuiraptor, noted that the bone closely resembled that of their new genus. This specimen is sometimes referred to as "Allosaurus robustus", an informal museum name. It likely belonged to something similar to Australovenator, although one study considered it to belong to an abelisaur. |
Allosaurus | Description | Description
thumb|left|The size range of Allosaurus compared with a human
Allosaurus was a typical large theropod, having a massive skull on a short neck, a long, slightly sloping tail, and reduced forelimbs. Allosaurus fragilis, the best-known species, had an average length of and mass of , with the largest definitive Allosaurus specimen (AMNH 680) estimated at long, with an estimated weight of . In his 1976 monograph on Allosaurus, James H. Madsen mentioned a range of bone sizes which he interpreted to show a maximum length of . As with dinosaurs in general, weight estimates are debatable, and since 1980 have ranged between , , and approximately for modal adult weight (not maximum). John Foster, a specialist on the Morrison Formation, suggests that is reasonable for large adults of A. fragilis, but that is a closer estimate for individuals represented by the average-sized thigh bones he has measured. Using the subadult specimen nicknamed "Big Al", since assigned to the species Allosaurus jimmadseni, researchers using computer modeling arrived at a best estimate of for the individual, but by varying parameters they found a range from approximately to approximately . A separate computational project estimated the adaptive optimum body mass in Allosaurus to be ~2,345 kg. A. europaeus has been measured up to in length and in body mass.
thumb|A. jimmadseni skeletal reconstruction
Several gigantic specimens have been attributed to Allosaurus, but may in fact belong to other genera. The dubious genus Saurophaganax (OMNH 1708) was estimated to reach around in length, and its single species was sometimes included in the genus Allosaurus as Allosaurus maximus. However, a 2024 study concluded that some material assigned to Saurophaganax actually belonged to a diplodocid sauropod with the material confidently assigned to Allosauridae belonging to a new species of Allosaurus, A. anax, and the body mass of this species was tentatively estimated around based on fragmentary material. Another potential specimen of Allosaurus, once assigned to the genus Epanterias (AMNH 5767), may have measured in length. A more recent discovery is a partial skeleton from the Peterson Quarry in Morrison rocks of New Mexico; this large allosaurid was suggested to be a potential specimen of Saurophaganax prior to this taxon's 2024 reassessment.Foster, John. 2007. Jurassic West: the Dinosaurs of the Morrison Formation and Their World. Bloomington, Indiana:Indiana University Press. p. 117.
David K. Smith, examining Allosaurus fossils by quarry, found that the Cleveland-Lloyd Dinosaur Quarry (Utah) specimens are generally smaller than those from Como Bluff (Wyoming) or Brigham Young University's Dry Mesa Quarry (Colorado), but the shapes of the bones themselves did not vary between the sites. A later study by Smith incorporating Garden Park (Colorado) and Dinosaur National Monument (Utah) specimens found no justification for multiple species based on skeletal variation; skull variation was most common and was gradational, suggesting individual variation was responsible. Further work on size-related variation again found no consistent differences, although the Dry Mesa material tended to clump together on the basis of the astragalus, an ankle bone. Kenneth Carpenter, using skull elements from the Cleveland-Lloyd site, found wide variation between individuals, calling into question previous species-level distinctions based on such features as the shape of the horns, and the proposed differentiation of A. jimmadseni based on the shape of the jugal. A study published by Motani et al., in 2020 suggests that Allosaurus was also sexually dimorphic in the width of the femur's head against its length. |
Allosaurus | Skull | Skull
thumb|A. jimmadseni skull with diagram highlighting individual bones
The skull and teeth of Allosaurus were modestly proportioned for a theropod of its size. Paleontologist Gregory S. Paul gives a length of for a skull belonging to an individual he estimates at long. Each premaxilla (the bones that formed the tip of the snout) held five teeth with D-shaped cross-sections, and each maxilla (the main tooth-bearing bones in the upper jaw) had between 14 and 17 teeth; the number of teeth does not exactly correspond to the size of the bone. Each dentary (the tooth-bearing bone of the lower jaw) had between 14 and 17 teeth, with an average count of 16. The teeth became shorter, narrower, and more curved toward the back of the skull. All of the teeth had saw-like edges. They were shed easily, and were replaced continually, making them common fossils. Its skull was light, robust and equipped with dozens of sharp, serrated teeth.
The skull had a pair of horns above and in front of the eyes. These horns were composed of extensions of the lacrimal bones, and varied in shape and size. There were also lower paired ridges running along the top edges of the nasal bones that led into the horns. The horns were probably covered in a keratin sheath and may have had a variety of functions, including acting as sunshades for the eyes, being used for display, and being used in combat against other members of the same species (although they were fragile). There was a ridge along the back of the skull roof for muscle attachment, as is also seen in tyrannosaurids.
Inside the lacrimal bones were depressions that may have held glands, such as salt glands. Within the maxillae were sinuses that were better developed than those of more basal theropods such as Ceratosaurus and Marshosaurus; they may have been related to the sense of smell, perhaps holding something like Jacobson's organs. The roof of the braincase was thin, perhaps to improve thermoregulation for the brain. The skull and lower jaws had joints that permitted motion within these units. In the lower jaws, the bones of the front and back halves loosely articulated, permitting the jaws to bow outward and increasing the animal's gape.Paul, Gregory S. (1988). Predatory Dinosaurs of the World. 91 and Figure 4–5 (93). The braincase and frontals may also have had a joint. |
Allosaurus | Postcranial skeleton | Postcranial skeleton
thumb|left|Life restoration of A. fragilis
Allosaurus had nine vertebrae in the neck, 14 in the back, and five in the sacrum supporting the hips.Madsen, 1976; note that not everyone agrees on where the neck ends and the back begins, and some authors such as Gregory S. Paul interpret the count as 10 neck and 13 back vertebrae. The number of tail vertebrae is unknown and varied with individual size; James Madsen estimated about 50, while Gregory S. Paul considered that to be too many and suggested 45 or less. There were hollow spaces in the neck and anterior back vertebrae. Such spaces, which are also found in modern theropods (that is, the birds), are interpreted as having held air sacs used in respiration. The rib cage was broad, giving it a barrel chest, especially in comparison to less derived theropods like Ceratosaurus.Paul, Gregory S. (1988). Predatory Dinosaurs of the World. 277. Allosaurus had gastralia (belly ribs), but these are not common findings, and they may have ossified poorly. In one published case, the gastralia show evidence of injury during life. A furcula (wishbone) was also present, but has only been recognized since 1996; in some cases furculae were confused with gastralia. The ilium, the main hip bone, was massive, and the pubic bone had a prominent foot that may have been used for both muscle attachment and as a prop for resting the body on the ground. Madsen noted that in about half of the individuals from the Cleveland-Lloyd Dinosaur Quarry, independent of size, the pubes had not fused to each other at their foot ends. He suggested that this was a sexual characteristic, with females lacking fused bones to make egg-laying easier. This proposal has not attracted further attention, however.
thumb|Hand and claws of A. fragilis
The forelimbs of Allosaurus were short in comparison to the hindlimbs (only about 35% the length of the hindlimbs in adults) and had three fingers per hand, tipped with large, strongly curved and pointed claws. The arms were powerful, and the forearm was somewhat shorter than the upper arm (1:1.2 ulna/humerus ratio). The wrist had a version of the semilunate carpal also found in more derived theropods like maniraptorans. Of the three fingers, the innermost (or thumb) was the largest, and diverged from the others. The phalangeal formula is 2-3-4-0-0, meaning that the innermost finger (phalange) has two bones, the next has three, and the third finger has four.Martin, A.J. (2006). Introduction to the Study of Dinosaurs. Second Edition. Oxford, Blackwell Publishing. 560 pp. . The legs were not as long or suited for speed as those of tyrannosaurids, and the claws of the toes were less developed and more hoof-like than those of earlier theropods. Each foot had three weight-bearing toes and an inner dewclaw, which Madsen suggested could have been used for grasping in juveniles. There was also what is interpreted as the splint-like remnant of a fifth (outermost) metatarsal, perhaps used as a lever between the Achilles tendon and foot.Paul, Gregory S. (1988). Predatory Dinosaurs of the World. 113; note illustrations of Allosaurus on 310 and 311 as well; Madsen (1976) interpreted these bones as possible upper portions of the inner metatarsal. |
Allosaurus | Skin | Skin
Skin impressions from Allosaurus have been described. One impression, from a juvenile specimen, measures 30 cm² and is associated with the anterior dorsal ribs/pectoral region. The impression shows small scales measuring 1–3 mm in diameter. A skin impression from the "Big Al Two" specimen, associated with the base of the tail, measures 20 cm × 20 cm and shows large scales measuring up to 2 cm in diameter. However, it has been noted that these scales are more similar to those of sauropods, and due to the presence of non-theropod remains associated with the tail of "Big Al Two" there is a possibility that this skin impression is not from Allosaurus.
Another Allosaurus fossil features a skin impression from the mandible, showing scales measuring 1–2 mm in diameter. The same fossil also preserves skin measuring 20 × 20 cm from the ventral side of the neck, showing scutate scales measuring 0.5 cm wide and 11 cm long. A small skin impression from an Allosaurus skull has been reported but never described. |
Allosaurus | Classification | Classification
thumb|right|upright=0.9|Life restoration of A. anax
Allosaurus was an allosaurid, a member of a family of large theropods within the larger group Carnosauria. The family name Allosauridae was created for this genus in 1878 by Othniel Charles Marsh, but the term was largely unused until the 1970s in favor of Megalosauridae, another family of large theropods that eventually became a wastebasket taxon. This, along with the use of Antrodemus for Allosaurus during the same period, is a point that needs to be remembered when searching for information on Allosaurus in publications that predate James Madsen's 1976 monograph. Major publications using the name "Megalosauridae" instead of "Allosauridae" include Gilmore, 1920, von Huene, 1926, Romer, 1956 and 1966, Steel, 1970, and Walker, 1964.
Following the publication of Madsen's influential monograph, Allosauridae became the preferred family assignment, but it too was not strongly defined. Semi-technical works used Allosauridae for a variety of large theropods, usually those that were larger and better-known than megalosaurids. Typical theropods that were thought to be related to Allosaurus included Indosaurus, Piatnitzkysaurus, Piveteausaurus, Yangchuanosaurus, Acrocanthosaurus, Chilantaisaurus, Compsosuchus, Stokesosaurus, and Szechuanosaurus. Given modern knowledge of theropod diversity and the advent of cladistic study of evolutionary relationships, none of these theropods is now recognized as an allosaurid, although several, like Acrocanthosaurus and Yangchuanosaurus, are members of closely related families.
thumb|Illustrations showing the skull of A. jimmadseni from the side (A), top (B), and back (C)
thumb|A. jimmadseni specimen "Big Al II" (SMA 0005)
Below is a cladogram based on the analysis of Benson et al. in 2010.
Allosauridae is one of four families in Allosauroidea; the other three are Neovenatoridae, Carcharodontosauridae and Sinraptoridae. Allosauridae has at times been proposed as ancestral to the Tyrannosauridae (which would make it paraphyletic), one example being Gregory S. Paul's Predatory Dinosaurs of the World,Paul, Gregory S. (1988). "The allosaur-tyrannosaur group", Predatory Dinosaurs of the World. 301–347. but this has been rejected, with tyrannosaurids identified as members of a separate branch of theropods, the Coelurosauria. Allosauridae is the smallest of the carnosaur families, with only Saurophaganax and a currently unnamed French allosauroid accepted as possible valid genera besides Allosaurus in the most recent review. Another genus, Epanterias, is a potential valid member, but it and Saurophaganax may turn out to be large examples of Allosaurus. Some reviews have kept the genus Saurophaganax and included Epanterias with Allosaurus.
The controversial Saurophaganax, initially recognized as a large Allosaurus-like theropod, has had a controversial taxonomic history. In 2019, Rauhut and Pol noted that its taxonomic placement within Allosauroidea is unstable, being recovered as a sister taxon of Metriacanthosauridae or Allosauria, or even as the basalmost carcharodontosaurian. Supplementary information In 2024, Saurophaganax was reassessed as a dubious, chimeric taxon with the holotype being so fragmentary that it could only be confidently referred to the Saurischia, and some specimens more likely belonging to a diplodocid sauropod. |
Allosaurus | Paleobiology | Paleobiology |
Allosaurus | Life history | Life history
thumb|left|Skeletons at different growth stages on display, the Natural History Museum of Utah
The wealth of Allosaurus fossils, from nearly all ages of individuals, allows scientists to study how the animal grew and how long its lifespan may have been. Remains may reach as far back in the lifespan as eggs—crushed eggs from Colorado have been suggested as those of Allosaurus. Based on histological analysis of limb bones, bone deposition appears to stop at around 22 to 28 years, which is comparable to that of other large theropods like Tyrannosaurus. From the same analysis, its maximum growth appears to have been at age 15, with an estimated growth rate of about 150 kilograms (330 lb) per year.
Medullary bone tissue (endosteally derived, ephemeral, mineralization located inside the medulla of the long bones in gravid female birds) has been reported in at least one Allosaurus specimen, a shin bone from the Cleveland-Lloyd Quarry. Today, this bone tissue is only formed in female birds that are laying eggs, as it is used to supply calcium to shells. Its presence in the Allosaurus individual has been used to establish sex and show it had reached reproductive age. However, other studies have called into question some cases of medullary bone in dinosaurs, including this Allosaurus individual. Data from extant birds suggested that the medullary bone in this Allosaurus individual may have been the result of a bone pathology instead. However, with the confirmation of medullary tissue indicating sex in a specimen of Tyrannosaurus, it may be possible to ascertain whether or not the Allosaurus in question was indeed female.
thumb|Restoration of a juvenile Allosaurus
The discovery of a juvenile specimen with a nearly complete hindlimb shows that the legs were relatively longer in juveniles, and the lower segments of the leg (shin and foot) were relatively longer than the thigh. These differences suggest that younger Allosaurus were faster and had different hunting strategies than adults, perhaps chasing small prey as juveniles, then becoming ambush hunters of large prey upon adulthood. The thigh bone became thicker and wider during growth, and the cross-section less circular, as muscle attachments shifted, muscles became shorter, and the growth of the leg slowed. These changes imply that juvenile legs has less predictable stresses compared with adults, which would have moved with more regular forward progression. Conversely, the skull bones appear to have generally grown isometrically, increasing in size without changing in proportion. |
Allosaurus | Feeding | Feeding
thumb|left|Bitten Stegosaurus plate close-up, showing how well the damage matches the front of an Allosaurus "mouth"
Most paleontologists accept Allosaurus as an active predator of large animals. There is dramatic evidence for allosaur attacks on Stegosaurus, including an Allosaurus tail vertebra with a partially healed puncture wound that fits a Stegosaurus tail spike, and a Stegosaurus neck plate with a U-shaped wound that correlates well with an Allosaurus snout. Sauropods seem to be likely candidates as both live prey and as objects of scavenging, based on the presence of scrapings on sauropod bones fitting allosaur teeth well and the presence of shed allosaur teeth with sauropod bones.Fastovsky, David E.; and Smith, Joshua B. (2004). "Dinosaur Paleoecology", in The Dinosauria (2nd ed.). 614–626. However, as Gregory Paul noted in 1988, Allosaurus was probably not a predator of fully grown sauropods, unless it hunted in packs, as it had a modestly sized skull and relatively small teeth, and was greatly outweighed by contemporaneous sauropods. Another possibility is that it preferred to hunt juveniles instead of fully grown adults. Research in the 1990s and the first decade of the 21st century may have found other solutions to this question. Robert T. Bakker, comparing Allosaurus to Cenozoic saber-toothed carnivorous mammals, found similar adaptations, such as a reduction of jaw muscles and increase in neck muscles, and the ability to open the jaws extremely wide. Although Allosaurus did not have saber teeth, Bakker suggested another mode of attack that would have used such neck and jaw adaptations: the short teeth in effect became small serrations on a saw-like cutting edge running the length of the upper jaw, which would have been driven into prey. This type of jaw would permit slashing attacks against much larger prey, with the goal of weakening the victim.
thumb|A. fragilis showing its maximum possible gape, based on Bakker (1998) and Rayfield et al. (2001)
Similar conclusions were drawn by another study using finite element analysis on an Allosaurus skull. According to their biomechanical analysis, the skull was very strong but had a relatively small bite force. By using jaw muscles only, it could produce a bite force of 805 to 8,724 N, but the skull could withstand nearly 55,500 N of vertical force against the tooth row. The authors suggested that Allosaurus used its skull like a machete against prey, attacking open-mouthed, slashing flesh with its teeth, and tearing it away without splintering bones, unlike Tyrannosaurus, which is thought to have been capable of damaging bones. They also suggested that the architecture of the skull could have permitted the use of different strategies against different prey; the skull was light enough to allow attacks on smaller and more agile ornithopods, but strong enough for high-impact ambush attacks against larger prey like stegosaurids and sauropods. Their interpretations were challenged by other researchers, who found no modern analogs to a hatchet attack and considered it more likely that the skull was strong to compensate for its open construction when absorbing the stresses from struggling prey. The original authors noted that Allosaurus itself has no modern equivalent, that the tooth row is well-suited to such an attack, and that articulations in the skull cited by their detractors as problematic actually helped protect the palate and lessen stress. Another possibility for handling large prey is that theropods like Allosaurus were "flesh grazers" which could take bites of flesh out of living sauropods that were sufficient to sustain the predator so it would not have needed to expend the effort to kill the prey outright. This strategy would also potentially have allowed the prey to recover and be fed upon in a similar way later. An additional suggestion notes that ornithopods were the most common available dinosaurian prey, and that Allosaurus may have subdued them by using an attack similar to that of modern big cats: grasping the prey with their forelimbs, and then making multiple bites on the throat to crush the trachea. This is compatible with other evidence that the forelimbs were strong and capable of restraining prey. Studies done by Stephen Lautenschager et al. from the University of Bristol also indicate Allosaurus could open its jaws quite wide and sustain considerable muscle force. When compared with Tyrannosaurus and the therizinosaurid Erlikosaurus in the same study, it was found that Allosaurus had a wider gape than either; the animal was capable of opening its jaws to a 92-degree angle at maximum. The findings also indicate that large carnivorous dinosaurs, like modern carnivores, had wider jaw gapes than herbivores.
left|thumb|Allosaurus and Stegosaurus skeletons, the Denver Museum of Nature and Science
A biomechanical study published in 2013 by Eric Snively and colleagues found that Allosaurus had an unusually low attachment point on the skull for the longissimus capitis superficialis neck muscle compared to other theropods such as Tyrannosaurus. This would have allowed the animal to make rapid and forceful vertical movements with the skull. The authors found that vertical strikes as proposed by Bakker and Rayfield are consistent with the animal's capabilities. They also found that the animal probably processed carcasses by vertical movements in a similar manner to falcons, such as kestrels: The animal could have gripped prey with the skull and feet, then pulled back and up to remove flesh. This differs from the prey-handling envisioned for tyrannosaurids, which probably tore flesh with lateral shakes of the skull, similar to crocodilians. In addition, Allosaurus was able to "move its head and neck around relatively rapidly and with considerable control", at the cost of power.
Other aspects of feeding include the eyes, arms, and legs. The shape of the skull of Allosaurus limited potential binocular vision to 20° of width, slightly less than that of modern crocodilians. As with crocodilians, this may have been enough to judge prey distance and time attacks. The arms, compared with those of other theropods, were suited for both grasping prey at a distance or clutching it close, and the articulation of the claws suggests that they could have been used to hook things. Finally, the top speed of Allosaurus has been estimated at per hour.
A paper on the cranio-dental morphology of Allosaurus and how it worked has deemed the hatchet jaw attack unlikely, reinterpreting the unusually wide gape as an adaptation to allow Allosaurus to deliver a muscle-driven bite to large prey, with the weaker jaw muscles being a trade-off to allow for the widened gape.
thumb|right|Restoration of Barosaurus rearing to defend itself against a pair of A. fragilis
Sauropod carrion may also have been important to large theropods in the Morrison Formation. Forensic techniques indicate that sauropod carcasses were targeted by Allosaurus at all stages of decomposition, indicating that late-stage decay pathogens were not a significant deterrent. A survey of sauropod bones from the Morrison Formation also reported widespread bite marks on sauropod bones in low-economy regions, which suggests that large theropods scavenged large sauropods when available, with the scarcity of such bite marks on the remains of smaller bones being potentially attributable to much more complete consumption of smaller or adolescent sauropods and on ornithischians, which would have been more commonly taken as live prey. A single dead adult Barosaurus or Brachiosaurus would have had enough calories to sustain multiple large theropods for weeks or months, though the vast majority of the Morrison's sauropod fossil record consisted of much smaller-bodied taxa such as Camarasaurus lentus or Diplodocus.
It has also been argued that disabled individuals such as Big Al and Big Al II were physically incapable of hunting due to their numerous injuries but were able to survive nonetheless as scavengers of giant sauropod-falls, Interestingly, a recent review of paleopathologies in theropods may support this conclusion. The researchers found a positive association between allosaurids and fractures to the appendicular skeleton, while tyrannosaurs had a statistically negative association with these types of injuries. The fact that allosaurs were more likely to survive and heal even when severe fractures limited their locomotion abilities can be explained, in part, by different resource accessibility paradigms for the two groups, as allosauroids generally lived in sauropod-inhabited ecosystems, some of which, including the Morrison, have been interpreted as arid and highly water-stressed environments; however, the water-stressed nature of the Morrison has been heavily criticized in several more recent works on the basis of fossil evidence for the presence of extensive forest cover and aquatic ecosystems. |
Allosaurus | Social behavior | Social behavior
thumb|left|The holotype dentary of Labrosaurus ferox, which may have been injured by the bite of another A. fragilis
It has been speculated since the 1970s that Allosaurus preyed on sauropods and other large dinosaurs by hunting in groups.
Such a depiction is common in semitechnical and popular dinosaur literature. Robert T. Bakker has extended social behavior to parental care, and has interpreted shed allosaur teeth and chewed bones of large prey animals as evidence that adult allosaurs brought food to lairs for their young to eat until they were grown, and prevented other carnivores from scavenging on the food. However, there is actually little evidence of gregarious behavior in theropods, and social interactions with members of the same species would have included antagonistic encounters, as shown by injuries to gastralia and bite wounds to skulls (the pathologic lower jaw named Labrosaurus ferox is one such possible example). Such head-biting may have been a way to establish dominance in a pack or to settle territorial disputes.
Although Allosaurus may have hunted in packs, it has been argued that Allosaurus and other theropods had largely aggressive interactions instead of cooperative interactions with other members of their own species. The study in question noted that cooperative hunting of prey much larger than an individual predator, as is commonly inferred for theropod dinosaurs, is rare among vertebrates in general, and modern diapsid carnivores (including lizards, crocodiles, and birds) rarely cooperate to hunt in such a way. Instead, they are typically territorial and will kill and cannibalize intruders of the same species, and will also do the same to smaller individuals that attempt to eat before they do when aggregated at feeding sites. According to this interpretation, the accumulation of remains of multiple Allosaurus individuals at the same site; e.g., in the Cleveland–Lloyd Quarry, are not due to pack hunting, but to the fact that Allosaurus individuals were drawn together to feed on other disabled or dead allosaurs, and were sometimes killed in the process. This could explain the high proportion of juvenile and subadult allosaurs present, as juveniles and subadults are disproportionally killed at modern group feeding sites of animals like crocodiles and Komodo dragons. The same interpretation applies to Bakker's lair sites. There is some evidence for cannibalism in Allosaurus, including Allosaurus shed teeth found among rib fragments, possible tooth marks on a shoulder blade, and cannibalized allosaur skeletons among the bones at Bakker's lair sites. On the other hand, pathological analysis done by Foth et al. argued evidence of surviving serious injuries may support gregariousness in Allosaurus. |
Allosaurus | Brain and senses | Brain and senses
thumb|right|Endocast (cast of the brain cavity) of Allosaurus
The brain of Allosaurus, as interpreted from spiral CT scanning of an endocast, was more consistent with crocodilian brains than those of the other living archosaurs, birds. The structure of the vestibular apparatus indicates that the skull was held nearly horizontal, as opposed to strongly tipped up or down. The structure of the inner ear was like that of a crocodilian, indicating that Allosaurus was more adapted to hear lower frequencies and would have had difficulty hearing subtle sounds. The olfactory bulbs were large and well suited for detecting odors, but were typical for an animal of its size. |
Allosaurus | Paleopathology | Paleopathology
thumb|Mounted A. fragilis skeleton (USNM 4734), which has several healed injuries
In 2001, Bruce Rothschild and others published a study examining evidence for stress fractures and tendon avulsions in theropod dinosaurs and the implications for their behavior. Since stress fractures are caused by repeated trauma rather than singular events they are more likely to be caused by the behavior of the animal than other kinds of injury. Stress fractures and tendon avulsions occurring in the forelimb have special behavioral significance since while injuries to the feet could be caused by running or migration, resistant prey items are the most probable source of injuries to the hand. Allosaurus was one of only two theropods examined in the study to exhibit a tendon avulsion, and in both cases the avulsion occurred on the forelimb. When the researchers looked for stress fractures, they found that Allosaurus had a significantly greater number of stress fractures than Albertosaurus, Ornithomimus or Archaeornithomimus. Of the 47 hand bones the researchers studied, three were found to contain stress fractures. Of the feet, 281 bones were studied and 17 were found to have stress fractures. The stress fractures in the foot bones "were distributed to the proximal phalanges" and occurred across all three weight-bearing toes in "statistically indistinguishable" numbers. Since the lower end of the third metatarsal would have contacted the ground first while an allosaur was running, it would have borne the most stress. If the allosaurs' stress fractures were caused by damage accumulating while walking or running this bone should have experience more stress fractures than the others. The lack of such a bias in the examined Allosaurus fossils indicates an origin for the stress fractures from a source other than running. The authors conclude that these fractures occurred during interaction with prey, like an allosaur trying to hold struggling prey with its feet. The abundance of stress fractures and avulsion injuries in Allosaurus provide evidence for "very active" predation-based rather than scavenging diets.Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p. 331–336.
The left scapula and fibula of an Allosaurus fragilis specimen cataloged as USNM 4734 are both pathological, both probably due to healed fractures. The specimen USNM 8367 preserved several pathological gastralia which preserve evidence of healed fractures near their middle. Some of the fractures were poorly healed and "formed pseudoarthroses". A specimen with a fractured rib was recovered from the Cleveland-Lloyd Quarry. Another specimen had fractured ribs and fused vertebrae near the end of the tail. An apparent subadult male Allosaurus fragilis was reported to have extensive pathologies, with a total of fourteen separate injuries. The specimen MOR 693 had pathologies on five ribs, the sixth neck vertebra, the third, eighth, and thirteenth back vertebrae, the second tail vertebra and its chevron, the gastralia right scapula, manual phalanx I left ilium metatarsals III and V, the first phalanx of the third toe and the third phalanx of the second. The ilium had "a large hole...caused by a blow from above". The near end of the first phalanx of the third toe was afflicted by an involucrum.
Additionally, a subadult Allosaurus individual that suffered from spondyloarthropathy has been discovered in Dana Quarry in Wyoming. This finding represents the first known fossil evidence of spondyloarthropathy occurring in a theropod.
thumb|Skeletal restoration of "Big Al II" showing bones with pathologies
Other pathologies reported in Allosaurus include:
Willow breaks in two ribs
Healed fractures in the humerus and radius
Distortion of joint surfaces in the foot, possibly due to osteoarthritis or developmental issues
Osteopetrosis along the endosteal surface of a tibia.
Distortions of the joint surfaces of the tail vertebrae, possibly due to osteoarthritis or developmental issues
"[E]xtensive 'neoplastic' ankylosis of caudals", possibly due to physical trauma, as well as the fusion of chevrons to centra
Coossification of vertebral centra near the end of the tail
Amputation of a chevron and foot bone, both possibly a result of bites
"[E]xtensive exostoses" in the first phalanx of the third toe
Lesions similar to those caused by osteomyelitis in two scapulae
Bone spurs in a premaxilla, ungual, and two metacarpals
Exostosis in a pedal phalanx possibly attributable to an infectious disease
A metacarpal with a round depressed fracture |
Allosaurus | Paleoecology | Paleoecology
thumb|left|Locations in the Morrison Formation (yellow) where Allosaurus remains have been found
Allosaurus was the most common large theropod in the vast tract of Western American fossil-bearing rock known as the Morrison Formation, accounting for 70 to 75% of theropod specimens, and as such was at the top trophic level of the Morrison food chain. The Morrison Formation is interpreted as a semiarid environment with distinct wet and dry seasons, and flat floodplains. Vegetation varied from river-lining forests of conifers, tree ferns, and ferns (gallery forests), to fern savannas with occasional trees such as the Araucaria-like conifer Brachyphyllum.
The Morrison Formation has been a rich fossil hunting ground. The flora of the period has been revealed by fossils of green algae, fungi, mosses, horsetails, ferns, cycads, ginkgoes, and several families of conifers. Animal fossils discovered include bivalves, snails, ray-finned fishes, frogs, salamanders, turtles, sphenodonts, lizards, terrestrial and aquatic crocodylomorphs, several species of pterosaur, numerous dinosaur species, and early mammals such as docodonts, multituberculates, symmetrodonts, and triconodonts. Dinosaurs known from the Morrison include the theropods Ceratosaurus, Ornitholestes, Tanycolagreus, and Torvosaurus, the sauropods Haplocanthosaurus, Camarasaurus, Cathetosaurus, Brachiosaurus, Suuwassea, Apatosaurus, Brontosaurus, Barosaurus, Diplodocus, Supersaurus, Amphicoelias, and Maraapunisaurus, and the ornithischians Camptosaurus, Dryosaurus, and Stegosaurus. Allosaurus is commonly found at the same sites as Apatosaurus, Camarasaurus, Diplodocus, and Stegosaurus. The Late Jurassic formations of Portugal where Allosaurus is present are interpreted as having been similar to the Morrison, but with a stronger marine influence. Many of the dinosaurs of the Morrison Formation are the same genera as those seen in Portuguese rocks (mainly Allosaurus, Ceratosaurus, Torvosaurus, and Stegosaurus), or have a close counterpart (Brachiosaurus and Lusotitan, Camptosaurus and Draconyx).
thumb|alt=Allosaurus and Ceratosaurus fighting|Dry season at the Mygatt-Moore Quarry showing Ceratosaurus (center) and Allosaurus fighting over the desiccated carcass of another theropod
Allosaurus coexisted with fellow large theropods Ceratosaurus and Torvosaurus in both the United States and Portugal. The three appear to have had different ecological niches, based on anatomy and the location of fossils. Ceratosaurus and Torvosaurus may have preferred to be active around waterways, and had lower, thinner bodies that would have given them an advantage in forest and underbrush terrains, whereas Allosaurus was more compact, with longer legs, faster but less maneuverable, and seems to have preferred dry floodplains. Ceratosaurus, better known than Torvosaurus, differed noticeably from Allosaurus in functional anatomy by having a taller, narrower skull with large, broad teeth. Allosaurus was itself a potential food item to other carnivores, as illustrated by an Allosaurus pubic foot marked by the teeth of another theropod, probably Ceratosaurus or Torvosaurus. The location of the bone in the body (along the bottom margin of the torso and partially shielded by the legs), and the fact that it was among the most massive in the skeleton, indicates that the Allosaurus was being scavenged.
A bone assemblage in the Upper Jurassic Mygatt-Moore Quarry preserves an unusually high occurrence of theropod bite marks, most of which can be attributed to Allosaurus and Ceratosaurus, while others could have been made by Torvosaurus given the size of the striations. While the position of the bite marks on the herbivorous dinosaurs is consistent with predation or early access to remains, bite marks found on Allosaurus material suggest scavenging, either from the other theropods or from another Allosaurus. The unusually high concentration of theropod bite marks compared to other assemblages could be explained either by a more complete utilization of resources during a dry season by theropods, or by a collecting bias in other localities. |
Allosaurus | References | References |
Allosaurus | External links | External links
Specimens, discussion, and references pertaining to Allosaurus fragilis at The Theropod Database
Utah State Fossil, Allosaurus , from Pioneer: Utah's Online Library
Restoration of MOR 693 ("Big Al") and muscle and organ restoration at Scott Hartman's Skeletal Drawing website
List of the many possible Allosaurus species...
Category:Allosauridae
Category:Lourinhã Formation
Category:Fossil taxa described in 1877
Category:Taxa named by Othniel Charles Marsh
Category:Symbols of Utah
Category:Dinosaur genera
Category:Morrison Formation
Category:Kimmeridgian dinosaurs
Category:Tithonian dinosaurs
Category:Dinosaurs of the United States
Category:Fossil taxa described in 2006
Category:Fossil taxa described in 2020 |
Allosaurus | Table of Content | mergefrom, Discovery and history, Early discoveries and research, Cleveland-Lloyd discoveries, Modern study, "Big Al" and "Big Al II", Portuguese discoveries, Species, Synonyms, Formerly assigned species and fossils, Description, Skull, Postcranial skeleton, Skin, Classification, Paleobiology, Life history, Feeding, Social behavior, Brain and senses, Paleopathology, Paleoecology, References, External links |
AK-47 | Short description | The AK-47, officially known as the Avtomat Kalashnikova (; also known as the Kalashnikov or just AK), is an assault rifle that is chambered for the 7.62×39mm cartridge. Developed in the Soviet Union by Russian small-arms designer Mikhail Kalashnikov, it is the originating firearm of the Kalashnikov (or "AK") family of rifles. After more than seven decades since its creation, the AK-47 model and its variants remain one of the most popular and widely used firearms in the world.
Design work on the AK-47 began in 1945. It was presented for official military trials in 1947, and, in 1948, the fixed-stock version was introduced into active service for selected units of the Soviet Army. In early 1949, the AK was officially accepted by the Soviet Armed Forces and used by the majority of the member states of the Warsaw Pact.
The model and its variants owe their global popularity to their reliability under harsh conditions, low production cost (compared to contemporary weapons), availability in virtually every geographic region, and ease of use. The AK has been manufactured in many countries and has seen service with armed forces as well as irregular forces and insurgencies throughout the world. , "of the estimated 500 million firearms worldwide, approximately 100 million belong to the Kalashnikov family, three-quarters of which are AK-47s". The model is the basis for the development of many other types of individual, crew-served, and specialized firearms. |
AK-47 | History | History |
AK-47 | Origins | Origins
During World War II, the Sturmgewehr 44 rifle used by German forces made a deep impression on their Soviet counterparts. The select-fire rifle was chambered for a new intermediate cartridge, the 7.92×33mm Kurz, and combined the firepower of a submachine gun with the range and accuracy of a rifle. On 15 July 1943, an earlier model of the Sturmgewehr was demonstrated before the People's Commissariat of Arms of the USSR. The Soviets were impressed with the weapon and immediately set about developing an intermediate caliber fully automatic rifle of their own, to replace the PPSh-41 submachine guns and outdated Mosin–Nagant bolt-action rifles that armed most of the Soviet Army.
The Soviets soon developed the 7.62×39mm M43 cartridge, used in the semi-automatic SKS carbine and the RPD light machine gun. Shortly after World War II, the Soviets developed the AK-47 rifle, which quickly replaced the SKS in Soviet service. Introduced in 1959, the AKM is a lighter stamped steel version and the most ubiquitous variant of the entire AK series of firearms. In the 1960s, the Soviets introduced the RPK light machine gun, an AK-type weapon with a stronger receiver, a longer heavy barrel, and a bipod, that eventually replaced the RPD light machine gun. |
AK-47 | Concept | Concept
Mikhail Kalashnikov began his career as a weapon designer in 1941 while recuperating from a shoulder wound that he received during the Battle of Bryansk. Kalashnikov himself stated..."I was in the hospital, and a soldier in the bed beside me asked: 'Why do our soldiers have only one rifle for two or three of our men when the Germans have automatics?' So I designed one. I was a soldier, and I created a machine gun for a soldier. It was called an Avtomat Kalashnikova, the automatic weapon of Kalashnikov—AK—and it carried the year of its first manufacture, 1947."
The AK-47 is best described as a hybrid of previous rifle technology innovations. "Kalashnikov decided to design an automatic rifle combining the best features of the American M1 Garand and the German StG 44." Kalashnikov's team had access to these weapons and did not need to "reinvent the wheel". Kalashnikov himself observed: "A lot of Russian Army soldiers ask me how one can become a constructor, and how new weaponry is designed. These are very difficult questions. Each designer seems to have his own paths, his own successes and failures. But one thing is clear: before attempting to create something new, it is vital to have a good appreciation of everything that already exists in this field. I myself have had many experiences confirming this to be so."
Some claimed that Kalashnikov copied designs like Bulkin's TKB-415 or Simonov's AVS-31. |
AK-47 | Early designs | Early designs
Kalashnikov started work on a submachine gun design in 1942 and a light machine gun design in 1943. Early in 1944, Kalashnikov was given some 7.62×39mm M43 cartridges and informed that other designers were working on weapons for this new Soviet small-arms cartridge. It was suggested that a new weapon might well lead to greater things. He then undertook work on the new rifle. In 1944, he entered a design competition with this new 7.62×39mm, semi-automatic, gas-operated, long-stroke piston carbine, strongly influenced by the American M1 Garand. The new rifle was in the same class as the SKS-45 carbine, with a fixed magazine and gas tube above the barrel. However, the new Kalashnikov design lost out to a Simonov design.
In 1946, a new design competition was initiated to develop a new rifle. Kalashnikov submitted a gas-operated rifle with a short-stroke gas piston above the barrel, a breechblock mechanism similar to his 1944 carbine, and a curved 30-round magazine. Kalashnikov's rifles, the AK-1 (with a milled receiver) and AK-2 (with a stamped receiver) proved to be reliable weapons and were accepted to a second round of competition along with other designs.
These prototypes (also known as the AK-46) had a rotary bolt, a two-part receiver with separate trigger unit housing, dual controls (separate safety and fire selector switches), and a non-reciprocating charging handle located on the left side of the weapon. This design had many similarities to the StG 44. In late 1946, as the rifles were being tested, one of Kalashnikov's assistants, Aleksandr Zaitsev, suggested a major redesign to improve reliability. At first, Kalashnikov was reluctant, given that their rifle had already fared better than its competitors. Eventually, however, Zaitsev managed to persuade Kalashnikov.
thumb|Trail prototype weapon with slab-sided steel magazine
In November 1947, the new prototypes (AK-47s) were completed. The rifle used a long-stroke gas piston above the barrel. The upper and lower receivers were combined into a single receiver. The selector and safety were combined into a single control lever/dust cover on the right side of the rifle and the bolt handle was attached to the bolt carrier. This simplified the design and production of the rifle. The first army trial series began in early 1948. The new rifle proved to be reliable under a wide range of conditions and possessed convenient handling characteristics. In 1949, it was adopted by the Soviet Army as the "7.62 mm Kalashnikov rifle (AK)". |
AK-47 | Further development | Further development
thumb|AKMS with a stamped Type 4B receiver (top) and an AK-47 with a milled Type 2A receiver
There were many difficulties during the initial phase of production. The first production models had stamped sheet metal receivers with a milled trunnion and butt stock insert and a stamped body. Difficulties were encountered in welding the guide and ejector rails, causing high rejection rates. Instead of halting production, a heavy2.6 lb milled from 6 lb stock. This was about 2.2 lb heavier than the stamped receiver. machined receiver was substituted for the sheet metal receiver. Even though production of these milled rifles started in 1951, they were officially referred to as AK-49, based on the date their development started, but they are widely known in the collectors' and current commercial market as "Type 2 AK-47". This was a more costly process, but the use of machined receivers accelerated production as tooling and labor for the earlier Mosin–Nagant rifle's machined receiver were easily adapted. Partly because of these problems, the Soviets were not able to distribute large numbers of the new rifles to soldiers until 1956. During this time, production of the interim SKS rifle continued.
Once the manufacturing difficulties of non-milled receivers had been overcome, a redesigned version designated the AKM (M for "modernized" or "upgraded"; in Russian: []) was introduced in 1959. This new model used a stamped sheet metal receiver and featured a slanted muzzle brake on the end of the barrel to compensate for muzzle rise under recoil. In addition, a hammer retarder was added to prevent the weapon from firing out of battery (without the bolt being fully closed), during rapid or fully automatic fire. This is also sometimes referred to as a "cyclic rate reducer", or simply "rate reducer", as it also has the effect of reducing the number of rounds fired per minute during fully automatic fire. The rifle was also roughly one-third lighter than the previous model.
Receiver type Description Type 1A/B The original stamped receiver for the AK-47 was first produced in 1948 and adopted in 1949. The 1B was modified for an underfolding stock with a large hole present on each side to accommodate the hardware for the under folding stock. Type 2A/B The first milled receiver was made from steel forging. It went into production in 1951 and production ended in 1957. The Type 2A has a distinctive socketed metal "boot" connecting the butt stock to the receiver and the milled lightning cut on the sides runs parallel to the barrel. Type 3A/B "Final" version of the AK milled receiver made from steel bar stock. It went into production in 1955. The most ubiquitous example of the AK milled receiver. The milled lightning cut on the sides is slanted to the barrel axis. Type 4A/B AKM receiver stamped from a smooth sheet of steel supported extensively by pins and rivets. It went into production in 1959. Overall, the most-used design in the construction of AK-series rifles.
Most licensed and unlicensed productions of the Kalashnikov assault rifle abroad were of the AKM variant, partially due to the much easier production of the stamped receiver. This model is the most commonly encountered, having been produced in much greater quantities. All rifles based on the Kalashnikov design are often colloquially referred to as "AK-47s" in the West and some parts of Asia, although this is only correct when applied to rifles based on the original three receiver types. In most former Eastern Bloc countries, the weapon is known simply as the "Kalashnikov" or "AK". The differences between the milled and stamped receivers includes the use of rivets rather than welds on the stamped receiver, as well as the placement of a small dimple above the magazine well for stabilization of the magazine. |
AK-47 | Replacement | Replacement
In 1974, the Soviets began replacing their AK-47 and AKM rifles with a newer design, the AK-74, which uses 5.45×39mm ammunition. This new rifle and cartridge had only started to be manufactured in Eastern European nations when the Soviet Union collapsed, drastically slowing the production of the AK-74 and other weapons of the former Soviet bloc. |
AK-47 | Design | Design
The AK-47 was designed to be a simple, reliable fully automatic rifle that could be manufactured quickly and cheaply, using mass production methods that were state of the art in the Soviet Union during the late 1940s. The AK-47 uses a long-stroke gas system generally associated with high reliability in adverse conditions. The large gas piston, generous clearance between moving parts, and tapered cartridge case design allow the gun to endure large amounts of foreign matter and fouling without failing to cycle. |
AK-47 | Cartridge | Cartridge
thumb|Wound Profiles of Russian small-arms ammunition compiled by Dr. Martin Fackler on behalf of the U.S. militaryThe AK fires the 7.62×39mm cartridge with a muzzle velocity of .
The cartridge weight is , and the projectile weight is . The original Soviet M43 bullets are 123-grain boat-tail bullets with a copper-plated steel jacket, a large steel core, and some lead between the core and the jacket. The AK has excellent penetration when shooting through heavy foliage, walls, or a common vehicle's metal body and into an opponent attempting to use these things as cover. The 7.62×39mm M43 projectile does not generally fragment when striking an opponent and has an unusual tendency to remain intact even after making contact with bone. The 7.62×39mm round produces significant wounding in cases where the bullet tumbles (yaws) in tissue, but produces relatively minor wounds in cases where the bullet exits before beginning to yaw. In the absence of yaw, the M43 round can pencil through tissue with relatively little injury.
Most, if not all, of the 7.62×39mm ammunition found today is of the upgraded M67 variety. This variety deleted the steel insert, shifting the center of gravity rearward, and allowing the projectile to destabilize (or yaw) at about , nearly earlier in tissue than the M43 round. This change also reduces penetration in ballistic gelatin to ~ for the newer M67 round versus ~ for the older M43 round. However, the wounding potential of M67 is mostly limited to the small permanent wound channel the bullet itself makes, especially when the bullet yaws. |
AK-47 | Operating mechanism | Operating mechanism
thumb|The gas-operated mechanism of a Norinco AK-47
To fire, the operator inserts a loaded magazine, pulls back and releases the charging handle, and then pulls the trigger. In semi-automatic, the firearm fires only once, requiring the trigger to be released and depressed again for the next shot. In fully automatic, the rifle continues to fire automatically cycling fresh rounds into the chamber until the magazine is exhausted or pressure is released from the trigger. After ignition of the cartridge primer and propellant, rapidly expanding propellant gases are diverted into the gas cylinder above the barrel through a vent near the muzzle. The build-up of gases inside the gas cylinder drives the long-stroke piston and bolt carrier rearward and a cam guide machined into the underside of the bolt carrier, along with an ejector spur on the bolt carrier rail guide, rotates the bolt approximately 35° and unlocks it from the barrel extension via a camming pin on the bolt. The moving assembly has about of free travel, which creates a delay between the initial recoil impulse of the piston and the bolt unlocking sequence, allowing gas pressures to drop to a safe level before the seal between the chamber and the bolt is broken. The AK-47 does not have a gas valve; excess gases are ventilated through a series of radial ports in the gas cylinder. Unlike many other rifle platforms, such as the AR-15 platform, the Kalashnikov platform bolt locking lugs are chamfered allowing for primary extraction upon bolt rotation which aids reliable feeding and extraction, albeit not with that much force due to the short distance the bolt carrier travels before acting on the locking lug. The Kalashnikov platform then uses an extractor claw along with a fin shaped ejector to eject the spent cartridge case. |
AK-47 | Barrel | Barrel
thumb|AK-47 barrel and its distinctive gas block with a horizontal row of gas relief ports
The rifle received a barrel with a chrome-lined bore and four right-hand grooves at a 240 mm (1 in 9.45 in) or 31.5 calibers rifling twist rate. The gas block contains a gas channel that is installed at a slanted angle with the bore axis. The muzzle is threaded for the installation of various muzzle devices such as a muzzle brake or a blank-firing adaptor. |
AK-47 | Gas block | Gas block
The gas block of the AK-47 features a cleaning rod capture or sling loop. Gas relief ports that alleviate gas pressure are placed horizontally in a row on the gas cylinder. |
AK-47 | Fire selector | Fire selector
thumb|left|upright|Việt Cộng soldier armed with an AK-47 with the fire selector in the safe setting
The fire selector is a large lever located on the right side of the rifle; it acts as a dust cover and prevents the charging handle from being pulled fully to the rear when it is on safe. It is operated by the shooter's right fore-fingers and has three settings: safe (up), full-auto (center), and semi-auto (down). The reason for this is that a soldier under stress will push the selector lever down with considerable force, bypassing the full-auto stage and setting the rifle to semi-auto. To set the AK-47 to full-auto requires the deliberate action of centering the selector lever. To operate the fire selector lever, right-handed shooters have to briefly remove their right hand from the pistol grip, which is ergonomically sub-optimal. Some AK-type rifles also have a more traditional selector lever on the left side of the receiver, just above the pistol grip. This lever is operated by the shooter's right thumb and has three settings: safe (forward), full-auto (center), and semi-auto (backward). |
AK-47 | Sights | Sights
thumb|Rear sight of a Chinese Type 56, featuring settings and omission of a battle zero setting
The AK-47 uses a notched rear tangent iron sight calibrated in increments from . The front sight is a post adjustable for elevation in the field. Horizontal adjustment requires a special drift tool and is done by the armory before the issue or if the need arises by an armorer after the issue. The sight line elements are approximately over the bore axis. The "point-blank range" battle zero setting "П" standing for постоянная (constant) on the 7.62×39mm AK-47 rear tangent sight element corresponds to a zero. These settings mirror the Mosin–Nagant and SKS rifles, which the AK-47 replaced. For the AK-47 combined with service cartridges, the 300 m battle zero setting limits the apparent "bullet rise" within approximately relative to the line of sight. Soldiers are instructed to fire at any target within this range by simply placing the sights on the center of mass (the belt buckle, according to Russian and former Soviet doctrine) of the enemy target. Any errors in range estimation are tactically irrelevant, as a well-aimed shot will hit the torso of the enemy soldier. Some AK-type rifles have a front sight with a flip-up luminous dot that is calibrated at , for improved night fighting. |
AK-47 | Furniture | Furniture
The AK-47 was originally equipped with a buttstock, handguard, and an upper heat guard made from solid wood. With the introduction of the Type 3 receiver the buttstock, lower handguard, and upper heat guard were manufactured from birch plywood laminates. Such engineered woods are stronger and resist warping better than the conventional one-piece patterns, do not require lengthy maturing, and are cheaper. The wooden furniture was finished with the Russian amber shellac finishing process. AKS and AKMS models featured a downward-folding metal butt-stock similar to that of the German MP40 submachine-gun, for use in the restricted space in the BMP infantry combat vehicle, as well as by paratroops. All 100 series AKs use plastic furniture with side-folding stocks. |
AK-47 | Magazines | Magazines
thumb|"Bakelite" rust-colored steel-reinforced 30-round plastic box 7.62×39mm AK magazines. Three magazines have an "arrow in triangle" Izhmash arsenal mark on the bottom right. The other magazine has a "star" Tula arsenal mark on the bottom right
The standard magazine capacity is 30 rounds. There are also 10-, 20-, and 40-round box magazines, as well as 75-round drum magazines.
The AK-47's standard 30-round magazines have a pronounced curve that allows them to smoothly feed ammunition into the chamber. Their heavy steel construction combined with "feed-lips" (the surfaces at the top of the magazine that control the angle at which the cartridge enters the chamber) machined from a single steel billet makes them highly resistant to damage. These magazines are so strong that "Soldiers have been known to use their mags as hammers, and even bottle openers". This contributes to the AK-47 magazine being more reliable but makes it heavier than U.S. and NATO magazines.
The early slab-sided steel AK-47 30-round detachable box magazines had sheet-metal bodies and weighed empty. The later steel AKM 30-round magazines had lighter sheet-metal bodies with prominent reinforcing ribs weighing empty. To further reduce weight, a lightweight magazine with an aluminum body with a prominent reinforcing waffle rib pattern weighing empty was developed for the AKM that proved to be too fragile, and the small issued amount of these magazines were quickly withdrawn from service. As a replacement steel-reinforced 30-round plastic 7.62×39mm box magazines were introduced. These rust-colored magazines weigh empty and are often mistakenly identified as being made of Bakelite (a phenolic resin), but were fabricated from two parts of AG-S4 molding compound (a glass-reinforced phenol-formaldehyde binder impregnated composite), assembled using an epoxy resin adhesive. Noted for their durability, these magazines did however compromise the rifle's camouflage and lacked the small horizontal reinforcing ribs running down both sides of the magazine body near the front that were added on all later plastic magazine generations. A second-generation steel-reinforced dark-brown (color shades vary from maroon to plum to near black) 30-round 7.62×39mm magazine was introduced in the early 1980s, fabricated from ABS plastic. The third generation steel-reinforced 30-round 7.62×39mm magazine is similar to the second generation, but is darker colored and has a matte non-reflective surface finish. The current issue is a steel-reinforced matte true black non- reflective surface finished 7.62×39mm 30-round magazine, fabricated from ABS plastic weighing empty.
Early steel AK-47 magazines are long; the later ribbed steel AKM and newer plastic 7.62×39mm magazines are about shorter.
The transition from steel to mainly plastic magazines yields a significant weight reduction and allows a soldier to carry more ammunition for the same weight.
Rifle Cartridge Weight of empty magazine Weight of loaded magazine Max. ammunition load* AK-47 (1949) 7.62×39mm slab-sided steel 30-rounds 11 magazines for 330 rounds AKM (1959) ribbed stamped-steel 30-rounds 12 magazines for 360 rounds AK-103 (1994) steel-reinforced plastic 30-rounds 13 magazines for 390 rounds
All 7.62×39mm AK magazines are backward compatible with older AK variants.
10.12 kg (22.3 lb) is the maximum amount of ammo that the average soldier can comfortably carry. It also allows for the best comparison of the three most common 7.62×39mm AK magazines.
Most Yugoslavian and some East German AK magazines were made with cartridge followers that hold the bolt open when empty; however, most AK magazine followers allow the bolt to close when the magazine is empty. |
AK-47 | Accessories | Accessories
thumb|left|AK-47 6H2 bayonet and scabbard
thumb|left|AK-47 with Kalashnikov grenade launcher mounted on the muzzle
Accessories supplied with the rifle include a long 6H3 bayonet featuring a long spear point blade. The AK-47 bayonet is installed by slipping the diameter muzzle ring around the muzzle and latching the handle down on the bayonet lug under the front sight base.
All current model AKM rifles can mount under-barrel 40 mm grenade launchers such as the GP-25 and its variants, which can fire up to 20 rounds per minute and have an effective range of up to 400 meters. The main grenade is the VOG-25 (VOG-25M) fragmentation grenade which has a 6 m (9 m) (20 ft (30 ft)) lethality radius. The VOG-25P/VOG-25PM ("jumping") variant explodes above the ground.
The AK-47 can also mount a (rarely used) cup-type grenade launcher, the Kalashnikov grenade launcher that fires standard RGD-5 Soviet hand grenades. The maximum effective range is approximately 150 meters. This launcher can also be used to launch tear gas and riot control grenades.
All current AKs (100 series) and some older models have side rails for mounting a variety of scopes and sighting devices, such as the PSO-1 Optical Sniper Sight. The side rails allow for the removal and remounting of optical accessories without interfering with the zeroing of the optic. However, the 100 series side folding stocks cannot be folded with the optics mounted. |
AK-47 | Characteristics | Characteristics |
AK-47 | Service life | Service life
The AK-47 and its variants have been and are made in dozens of countries, with "quality ranging from finely engineered weapons to pieces of questionable workmanship." As a result, the AK-47 has a service/system life of approximately 6,000, to 10,000, to 15,000 rounds. The AK-47 was designed to be a cheap, simple, easy-to-manufacture rifle, perfectly matching Soviet military doctrine that treats equipment and weapons as disposable items. As units are often deployed without adequate logistical support and dependent on "battlefield cannibalization" for resupply, it is more cost-effective to replace rather than repair weapons.
The AK-47 has small parts and springs that need to be replaced every few thousand rounds. However, "Every time it is disassembled beyond the field stripping stage, it will take some time for some parts to regain their fit, and some parts may tend to shake loose and fall out when firing the weapon. Some parts of the AK-47 line are riveted together. Repairing these can be quite a hassle since the end of the rivet has to be ground off and a new one set after the part is replaced." |
AK-47 | Variants | Variants
thumb|7.62×39mm cartridges from Russia, China and Pakistan
Early variants (7.62×39mm)
Issue of 1948/49: Type 1: The very earliest models, stamped sheet metal receivers, are now very rare.
Issue of 1951: Type 2: Has a milled receiver. The barrel and chamber are chrome-plated to resist corrosion.
Issue of 1954/55: Type 3: Lightened, milled receiver variant. Rifle weight is .
AKS (AKS-47): Type 1, 2, or 3 receivers: Featured a downward under folding metal stock similar to that of the MP 40, for use in the restricted space of the BMP infantry combat vehicle, as well as for airborne troops.
AKN (AKSN): Night sight rail.
Modernized (7.62×39mm)
AKM: A simplified, lighter version of the AK-47; the Type 4 receiver is made from stamped and riveted sheet metal. A slanted muzzle device was added to reduce muzzle rise in automatic fire. The rifle weight is due to the lighter receiver. This is the most ubiquitous variant of the AK-47.
AKMS: Under-folding stock version of the AKM intended for airborne troops.
AKMN (AKMSN): Night scope rail.
AKML (AKMSL): Slotted flash suppressor and night scope rail.
RPK: Hand-held machine gun version with longer barrel and bipod. The variants—RPKS, RPKN (RPKSN), RPKL (RPKSL)—mirror AKM variants. The "S" variants have a side-folding wooden stock.
Foreign Variants (7.62×39mm)
Type 56: Chinese assault rifle based on the . Still in production primarily for export markets.
For the further developed AK models, see Kalashnikov rifles. |
AK-47 | Production | Production
Manufacturing countries of AK-47 and its variants in alphabetical order.
Country Military variant(s) Albania Automatiku Shqiptar 1978 model 56 (ASH-78 Tip-1) made at Poliçan Arsenal (copy of Type 56 based on AKM rifle); model 56 Tip-2, copy of RPK; model 56 Tip-3 hybrid for multi-purpose roles with secondary rifle and grenade launcher capability; 1982 model (ASH-82) copy of AKMS. Several other versions of the AKMS have been produced mainly with short barrels similar to Soviet AKS-74U for special forces, tank & armoured crew and for helicopter pilots and police. There have also been modified ASh-82 (AKMS) with SOPMOD accessories, mainly for Albania's special forces RENEA & exports. Armenia K-3 (bullpup, 5.45×39mm) Azerbaijan Khazri (AK-74M) Bangladesh Chinese Type 56 Bulgaria AKK/AKKS (Type 3 AK-47/w. side-folding buttstock); AKKMS (AKMS), AKKN-47 (fittings for NPSU night sights); AK-47M1 (Type 3 with black polymer furniture); AK-47MA1/AR-M1 (same as -M1, but in 5.56mm NATO); AKS-47M1 (AKMS in 5.56×45mm NATO); AKS-47S (AK-47M1, short version, with East German folding stock, laser aiming device); AKS-47UF (short version of -M1, Russian folding stock), AR-SF (same as −47UF, but 5.56mm NATO); AKS-93SM6 (similar to −47M1, cannot use grenade launcher); and RKKS (RPK), AKT-47 (.22 rimfire training rifle) Cambodia Chinese Type 56, Soviet AK-47, and AKM China Type 56 Colombia Galil ACE, Galil Córdova Croatia APS-95 Cuba AKM East Germany MPi-K/MPi-KS (AK-47/AKS); MPi-KM (AKM; wooden and plastic stock), MPi-KMS-72 (side-folding stock), MPi-KMS-K (carbine); MPi-AK-74N (AK-74), MPi-AKS-74N (side-folding stock), MPi-AKS-74NK (carbine); KK-MPi Mod.69 (.22 LR select-fire trainer) Egypt AK-47, Misr rifle (AKMS), Maadi ARM (AKM) Ethiopia AK-47, AK-103 (manufactured locally at the State-run Gafat Armament Engineering Complex as the Et-97/1) Finland Rk 62, Valmet M76 (other names Rk 62 76, M62/76), Valmet M78 (light machine gun), Rk 95 Tp Hungary AK-55 (domestic manufacture of the 2nd Model AK-47); AKM-63 (also known as AMD-63 in the US; modernized AK-55), AMD-65M (modernized AKM-63, shorter barrel and side-folding stock), AMP-69 (rifle grenade launcher); AK-63F/D (other name AMM/AMMSz), AK-63MF (modernized); NGM-81 (5.56×45mm NATO; fixed and under-folding stock) India INSAS (fixed and side-folding stock), KALANTAK (carbine), INSAS light machine gun (fixed and side-folding stock), a local unlicensed version with carbon fibre furniture designated as AK-7; and Trichy Rifle 7.62 mm manufactured by Ordnance Factory Tiruchirappalli of Ordnance Factories Board Iran KLS/KLF (AK-47/AKS), KLT (AKMS) Iraq Tabuk Sniper Rifle, Tabuk Rifle (with fixed or underfolding stock, outright clones of Yugoslavian M70 rifles series), Tabuk Short Rifle (carbine) Israel IMI Galil: AR (battle rifle), ARM (rifle/light machine gun), SAR (carbine), MAR (compact carbine), Sniper (sniper rifle), SR-99 (sniper rifle); and Galil ACE Italy Bernardelli VB-STD/VB-SR (Galil AR/SAR) Nigeria Produced by DICON as OBJ-006 North Korea Type 58A/B (Type 3 AK-47/w. stamped steel folding stock), Type 68A/B (AKM/AKMS), Type 88A/B-2 (AK-74/AKS-74/w. top folding stock) Pakistan Reverse engineered by hand and machine in Pakistan's highland areas (see Khyber Pass Copy) near the border of Afghanistan; more recently the Pakistan Ordnance Factories started the manufacture of an AK-47/AKM clone called PK-10 Poland PmK (kbk AK) / PmKS (kbk AKS), Kalashnikov SMG name change to Kbk AK, Kalashnikov Carbine in 1960s, (AK-47/AKS); kbkg wz. 1960 (rifle grenade launcher), kbkg wz. 1960/72 (modernized); kbk AKM / kbk AKMS (AKM/AKMS); kbk wz. 1988 Tantal (5.45×39mm), skbk wz. 1989 Onyks (compact carbine); kbs wz. 1996 Beryl (5.56×45mm), kbk wz. 1996 Mini-Beryl (compact carbine) Romania PM md. 63/65 (AKM/AKMS), PM md. 80, PM md. 90, collectively exported under the umbrella name AIM or AIMS; PA md. 86 (AK-74) exported as the AIMS-74; PM md. 90 short barrel, PA md. 86 short barrel exported as the AIMR; PSL (designated marksman rifle; other names PSL-54C, Romak III, FPK and SSG-97) South Africa R4 rifle, Truvelo Raptor, Vektor CR-21 (bullpup) Sudan MAZ (based on the Type 56) Türkiye SAR 15T, SAR 308 Ukraine Vepr (bullpup, 5.45×39mm), Malyuk (bullpup) United States Century Arms: C39 (AK-47 var.), RAS47 (AKM var.), and C39v2 (AK-47 var.), InterOrdnance: AKM247 (AKM var.) M214 (pistol), Palmetto State Armory: PSAK-47 (AKM var.), Arsenal Inc: SA M-7 (AK-47 var.), Destructive Devices Industries: DDI 47S (AKM var.) DDI 47M (AK-47 var), Rifle Dynamics: RD700 and other custom build AK / AKM guns Vietnam AKM-1 (AKM), TUL-1 (RPK), Galil Ace 31/32, STV rifle Venezuela License granted, factory under construction Yugoslavia/Serbia M64, M70, M72, M76, M77, M80, M82, M85, M90, M91, M92, M99, M21
A private company Kalashnikov Concern (formerly Izhmash) from Russia has repeatedly claimed that the majority of foreign manufacturers are producing AK-type rifles without proper licensing. |
AK-47 | Accuracy potential | Accuracy potential |
AK-47 | US military method | US military method
The AK-47's accuracy is generally sufficient to hit an adult male torso out to about , though even experts firing from prone or bench rest positions at this range were observed to have difficulty placing ten consecutive rounds on target. Later designs did not significantly improve the rifle's accuracy. An AK can fire a 10-shot group of at , and at The newer stamped-steel receiver AKM models, while more rugged and less prone to metal fatigue, are less accurate than the forged/milled receivers of their predecessors: the milled AK-47s are capable of shooting groups at , whereas the stamped AKMs are capable of shooting groups at .
The best shooters can hit a man-sized target at within five shots (firing from a prone or bench rest position) or ten shots (standing).: (under the default conditions of no wind and sea level atmospheric pressure, ).
The single-shot hit-probability on the NATO E-type Silhouette Target (a human upper body half and head silhouette) of the AK-47 and the later developed AK-74, M16A1, and M16A2 rifles were measured by the US military under ideal proving ground conditions in the 1980s as follows:
thumb|75 px|NATO E-type Silhouette Target
+Single-shot hit-probability on Crouching Man (NATO E-type Silhouette) TargetRifleChamberingHit-probability (With no range estimation or aiming errors) 50 m 100 m 200 m 300 m 400 m 500 m 600 m 700 m 800 mAK-47 (1949)7.62×39mm100%100%99%94%82%67%54%42%31%AK-74 (1974)5.45×39mm100%100%100%99%93%81%66%51%34%M16A1 (1967)5.56×45mm NATO M193100%100%100%100%96%87%73%56%39%M16A2 (1982)5.56×45mm NATO SS109/M855100%100%100%100%98%90%79%63%43%
Under worst field exercise circumstances, the hit probabilities for all the tested rifles were drastically reduced, from 34% at 50m down to 3–4% at 600m with no significant differences between weapons at each range. |
AK-47 | Russian method | Russian method
The following table represents the Russian circular error probable method for determining accuracy, which involves drawing two circles on the target, one for the maximum vertical dispersion of hits and one for the maximum horizontal dispersion of hits. They then disregard the hits on the outer part of the target and only count half of the hits (50% or R50) on the inner part of the circles. This significantly reduces the overall diameter of the groups. They then use both the vertical and horizontal measurements of the reduced groups to measure accuracy. When the R50 results are doubled, the hit probability increases to 93.7%.
thumb|right|Circular error probable 20 hits distribution example
+AK-47 semi-automatic and short burst dispersion with 57-N-231 steel core service ammunitionRangeVertical accuracy of fire (R50) semi-automaticHorizontal accuracy of fire (R50) semi-automaticVertical accuracy of fire (R50) short burstHorizontal accuracy of fire (R50) short burstRemaining bullet energyRemaining bullet velocity
R50 means the closest 50 percent of the shot group will all be within a circle of the mentioned diameter.
The vertical and horizontal mean (R50) deviations with service ammunition at for AK platforms are.
+SKS, AK-47, AKM, and AK-74 dispersion at Manual on small business. 7.62-mm modernized Kalashnikov assault rifle (AKM and AKMS). – 3rd ed. – Moscow: Military Publishing, 1983. – 160 p., Ill.RifleFiring modeVertical accuracy of fire (R50)Horizontal accuracy of fire (R50)SKS (1945)semi-automaticAK-47 (1949)semi-automaticAK-47 (1949)short burstAKM (1959)short burstAK-74 (1974)short burst |
AK-47 | Users | Users
thumb|A map of current AK users (including derivative and modernized variants in orange and purple) |
AK-47 | Current | Current
− Type 56 variant.
− EKAM: The counter-terrorist unit of the Hellenic Police
− Type 58 variant
– Locally made as well as being in service with the Army
− Used by Thahan Phran
|
AK-47 | Non-state current | Non-state current
ELN
FARC dissidents
− Captured from the Syrian Army
Karen National Defence Organisation
Karen National Liberation Army
Kurdistan Workers Party
National Movement for the Liberation of Azawad
New People's Army
Syrian opposition
Ta'ang National Liberation Army |
AK-47 | Former | Former
− MPi-K (AK-47) and MPi-KM (AKM)
− Passed on to the unified Vietnamese state
− Used by the Panama Defense Forces
− Replaced by the AKM and AK-74
− Captured rifles were issued to ARVN irregular units |
AK-47 | Non-state former | Non-state former
Afghan mujahideen − CIA supplied Egyptian and Chinese variants
Contras
Farabundo Martí National Liberation Front
Iraqi insurgents
Khmer Rouge
Liberation Tigers of Tamil Eelam
Malayan National Liberation Army
Moro National Liberation Front
Northern Alliance
Provisional Irish Republican Army − Supplied by Libya
RENAMO
Revolutionary Armed Forces of Colombia
Viet Cong
Vigorous Burmese Student Warriors |
AK-47 | Illicit trade | Illicit trade
thumb|AK-47 copies confiscated from Somali pirates by Finnish mine-layer during Operation Atalanta, photographed in Manege Military Museum. The stocks are missing on the top three AKs.
Throughout the world, the AK and its variants are commonly used by governments, revolutionaries, terrorists, criminals, and civilians alike. In some countries, such as Somalia, Rwanda, Mozambique, Congo, and Tanzania, the prices for Black Market AKs are between $30 and $125 per weapon and prices have fallen in the last few decades due to mass counterfeiting. In Kenya, "an AK-47 fetches five head of cattle (about 10,000 Kenya shillings or 100 U.S. dollars) when offered for barter, but costs almost half that price when cash is paid". There are places around the world where AK-type weapons can be purchased on the black market "for as little as $6, or traded for a chicken or a sack of grain".
The AK-47 has also spawned a cottage industry of sorts and has been copied and manufactured (one gun at a time) in small shops around the world (see Khyber Pass Copy). The estimated numbers of AK-type weapons vary greatly. The Small Arms Survey suggests that "between 70 and 100 million of these weapons have been produced since 1947". The World Bank estimates that out of the 500 million total firearms available worldwide, 100 million are of the Kalashnikov family, and 75 million are AK-47s. Because AK-type weapons have been made in many countries, often illicitly, it is impossible to know how many exist. |
AK-47 | Conflicts | Conflicts
The AK-47 has been used in the following conflicts:
1940s
Malayan Emergency (1948−1960)
1950s
Hungarian Revolution (1956)
Vietnam War (1955–1975)
Laotian Civil War (1959–1975)
1960s
Congo Crisis (1960–1965)
Portuguese Colonial War (1961–1974)
Rhodesian Bush War (1964–1979)
The Troubles (late 1960s–1998)
Communist insurgency in Thailand (1965–1983)
South African Border War (1966–1990)
India-China clashes (1967)
Cambodian Civil War (1968–1975)
Communist insurgency in Malaysia (1968–1989)
Moro conflict (1968−2019)
1970s
Yom Kippur War (1973)
Ethiopian Civil War (1974–1991)
Western Sahara War (1975–1991)
Cambodian–Vietnamese War (1978–1989)
Chadian–Libyan War (1978–1987)
Soviet–Afghan War (1979–1989)
1980s
1979 Kurdish rebellion in Iran
Iran–Iraq War (1980–1988)
Insurgency in Jammu and Kashmir (1988–present)
Sri Lankan Civil War (1983–2009)
United States invasion of Grenada (1983)
South Lebanon conflict (1985–2000)
Lord's Resistance Army insurgency (1987–present)
United States invasion of Panama (1989)
1990s
KDPI insurgency (1989–1996)
Tuareg rebellion (1990–1995)
Gulf War (1990–1991)
Somali Civil War (1991–present)
Yugoslav Wars (1991–2001)
Burundian Civil War (1993–2005)
First Chechen War (1994−1996)
Republic of the Congo Civil War (1997–1999)
Kargil War (1999)
2000s
War in Afghanistan (2001–2021)
Iraq War (2003–2011)
South Thailand insurgency (2004–present)
Mexican drug war (2006–present)
2010s
Libyan Civil War (2011)
Syrian civil war (2011–present)
Iraqi insurgency (2011–2013)
Central African Republic Civil War (2012–present)
Mali War (2012–present)
Russo-Ukrainian War (2014–present)
Western Iran clashes (2016–present)
2020s
Second Nagorno-Karabakh War (2020)
Tigray War (2020–2022)
Myanmar civil war (2021–present)
Russian invasion of Ukraine (2022–present)
September–October 2022 attacks on Iraqi Kurdistan
Israel-Hamas War (2023–present) |
AK-47 | Cultural influence and impact | Cultural influence and impact
thumb|The AK-47 on the flag of Mozambique
thumb|The AK-47 on the former coat of arms of Burkina Faso
thumb|CIA Agent drawing of the alleged first westerner sighting of the AK-47 in 1953
During the Cold War, the Soviet Union and the People's Republic of China, as well as United States and other NATO nations supplied arms and technical knowledge to numerous countries and rebel forces around the world. During this time the Western countries used relatively expensive automatic rifles, such as the FN FAL, the HK G3, the M14, and the M16. In contrast, the Russians and Chinese used the AK-47; its low production cost and ease of manufacture allow them to make AKs in vast numbers.
In the pro-communist states, the AK-47 became a symbol of the Third World revolution. They were utilized in the Cambodian Civil War and the Cambodian–Vietnamese War. During the 1980s, the Soviet Union became the principal arms dealer to countries embargoed by Western nations, including Middle Eastern nations such as Libya and Syria, which welcomed Soviet Union backing against Israel. After the fall of the Soviet Union, AK-47s were sold both openly and on the black market to any group with cash, including drug cartels and dictatorial states, and more recently they have been seen in the hands of Islamic groups such as Al-Qaeda, ISIL, and the Taliban in Afghanistan and Iraq, and FARC, Ejército de Liberación Nacional guerrillas in Colombia.
In Russia, the Kalashnikov is a tremendous source of national pride. "The family of the inventor of the world's most famous rifle, Mikhail Kalashnikov, has authorized German engineering company MMI to use the well-known Kalashnikov name on a variety of not-so-deadly goods." In recent years, Kalashnikov Vodka has been marketed with souvenir bottles in the shape of the AK-47 Kalashnikov. There are also Kalashnikov watches, umbrellas, and knives.
The Kalashnikov Museum (also called the AK-47 museum) opened on 4 November 2004 in Izhevsk, Udmurt Republic. This city is in the Ural Region of Russia. The museum chronicles the biography of General Kalashnikov and documents the invention of the AK-47. The museum complex of Kalashnikov's small arms, a series of halls, and multimedia exhibitions are devoted to the evolution of the AK-47 rifle and attracts 10,000 monthly visitors. Nadezhda Vechtomova, the museum director, stated in an interview that the purpose of the museum is to honor the ingenuity of the inventor and the hard work of the employees and to "separate the weapon as a weapon of murder from the people who are producing it and to tell its history in our country".
On 19 September 2017 a monument of Kalashnikov was unveiled in central Moscow. A protester, later detained by police, attempted to unfurl a banner reading "a creator of weapons is a creator of death".
The proliferation of this weapon is reflected by more than just numbers. The AK-47 is included on the flag of Mozambique and its emblem, an acknowledgment that the country gained its independence in large part through the effective use of their AK-47s. It is also found in the coats of arms of East Timor, Zimbabwe and the revolution era Burkina Faso, as well as in the flags of Hezbollah, Syrian Resistance, FARC-EP, the New People's Army, TKP/TIKKO and the International Revolutionary People's Guerrilla Forces.
U.S. and Western Europe countries frequently associate the AK-47 with their enemies; both Cold War era and present-day. For example, Western works of fiction (movies, television, novels, video games) often portray criminals, gang members, insurgents, and terrorists using AK-47s as the weapon of choice. Conversely, throughout the developing world, the AK-47 can be positively attributed with revolutionaries against foreign occupation, imperialism, or colonialism.
In Ireland the AK-47 is associated with The Troubles due to its extensive use by republican paramilitaries during this period. In 2013, a decommissioned AK-47 was included in the A History of Ireland in 100 Objects collection.
The AK-47 made an appearance in U.S. popular culture as a recurring focus in the Nicolas Cage film Lord of War (2005). Numerous monologues in the movie focus on the weapon, and its effects on global conflict and the gun running market.
In Iraq and Afghanistan, private military company contractors from the U.K. and other countries used the AK-47 and its variants along with Western firearms such as the AR-15.
In 2006, the Colombian musician and peace activist César López devised the escopetarra, an AK converted into a guitar. One sold for US$17,000 in a fundraiser held to benefit the victims of anti-personnel mines, while another was exhibited at the United Nations' Conference on Disarmament.
In Mexico, the AK-47 is known as "Cuerno de Chivo" (literally "Goat's Horn") because of its curved magazine design. It is one of the weapons of choice of Mexican drug cartels. It is sometimes mentioned in Mexican folk music lyrics. |
AK-47 | Gallery | Gallery |
AK-47 | See also | See also
Comparison of the AK-47 and M16
AK-12
PK machine gun
Draco |
AK-47 | Notes | Notes |
AK-47 | References | References |
AK-47 | Bibliography | Bibliography
|
AK-47 | Further reading | Further reading
Ружье. Оружие и амуниция, 1999/3, pp. 18–21 has an article about the AK-47 prototypes.
An article rejecting some of the alternative theories as to the authorship of the AK-47.
An article comparing the internals of the StG 44 and AK-47.
Transcription of the commission report on the testing round from the summer of 1947; no winner was selected at this point, but the commission held Kalashnikov's, Dementiev's and Bulkin's designs as most closely satisfying TTT number 3131.
Report/letter on the final round of testing, 27 December 1947, declaring Kalashnikov's design the winner.
Articles on the 1948 military trials. |
AK-47 | External links | External links
US Army Operator's Manual for the AK-47 Assault Rifle
&
Category:Weapons and ammunition introduced in 1947
Category:7.62×39mm assault rifles
Category:Infantry weapons of the Cold War
Category:Rifles of the Cold War
Category:Kalashnikov derivatives
Category:Assault rifles of the Soviet Union
Category:Kalashnikov Concern products
Category:Long stroke piston firearms |
AK-47 | Table of Content | Short description, History, Origins, Concept, Early designs, Further development, Replacement, Design, Cartridge, Operating mechanism, Barrel, Gas block, Fire selector, Sights, Furniture, Magazines, Accessories, Characteristics, Service life, Variants, Production, Accuracy potential, US military method, Russian method, Users, Current, Non-state current, Former, Non-state former, Illicit trade, Conflicts, Cultural influence and impact, Gallery, See also, Notes, References, Bibliography, Further reading, External links |
Atanasoff–Berry computer | short description | The Atanasoff–Berry computer (ABC) was the first automatic electronic digital computer. The device was limited by the technology of the day. The ABC's priority is debated among historians of computer technology, because it was neither programmable, nor Turing-complete. Conventionally, the ABC would be considered the first electronic ALU (arithmetic logic unit) which is integrated into every modern processor's design.
Its unique contribution was to make computing faster by being the first to use vacuum tubes to do arithmetic calculations. Prior to this, slower electro-mechanical methods were used by Konrad Zuse's Z1 computer, and the simultaneously developed Harvard Mark I. The first electronic, programmable, digital machine,Colossus and the German Lorenz Cypher. Anthony Sale, Bletchley Park Trust. the Colossus computer from 1943 to 1945, used similar tube-based technology as ABC. |
Atanasoff–Berry computer | Overview | Overview
Conceived in 1937, the machine was built by Iowa State College mathematics and physics professor John Vincent Atanasoff with the help of graduate student Clifford Berry. It was designed only to solve systems of linear equations and was successfully tested in 1942. However, its intermediate result storage mechanism, a paper card writer/reader, was not perfected, and when John Vincent Atanasoff left Iowa State College for World War II assignments, work on the machine was discontinued. The ABC pioneered important elements of modern computing, including binary arithmetic and electronic switching elements, but its special-purpose nature and lack of a changeable, stored program distinguish it from modern computers. The computer was designated an IEEE Milestone in 1990.
Atanasoff and Berry's computer work was not widely known until it was rediscovered in the 1960s, amid patent disputes over the first instance of an electronic computer. At that time ENIAC, that had been created by John Mauchly and J. Presper Eckert,John Presper Eckert Jr. and John W. Mauchly, Electronic Numerical Integrator and Computer, , filed 26 June 1947, issued 4 February 1964, and invalidated 19 October 1973 after court ruling on Honeywell v. Sperry Rand. was considered to be the first computer in the modern sense, but in 1973 a U.S. District Court invalidated the ENIAC patent and concluded that the ENIAC inventors had derived the subject matter of the electronic digital computer from Atanasoff. When, in the mid-1970s, the secrecy surrounding the British World War II development of the Colossus computers that pre-dated ENIAC, was liftedRandell, Brian, Colossus: Godfather of the Computer, 1977 (reprinted in The Origins of Digital Computers: Selected Papers, Springer-Verlag, New York, 1982) and Colossus was described at a conference in Los Alamos, New Mexico, in June 1976, John Mauchly and Konrad Zuse were reported to have been astonished. Report of the announcement of Colossus at the International Research Conference on the History of Computing, in Los Alamos, New Mexico, that began on 10 June 1976 |
Atanasoff–Berry computer | Design and construction | Design and construction
thumb|right|Diagram of the ABC pointing out its various components
According to Atanasoff's account, several key principles of the Atanasoff–Berry computer were conceived in a sudden insight after a long nighttime drive to Rock Island, Illinois, during the winter of 1937–38. The ABC innovations included electronic computation, binary arithmetic, parallel processing, regenerative capacitor memory, and a separation of memory and computing functions. The mechanical and logic design was worked out by Atanasoff over the next year. A grant application to build a proof of concept prototype was submitted in March 1939 to the Agronomy department, which was also interested in speeding up computation for economic and research analysis. $5,000 of further funding () to complete the machine came from the nonprofit Research Corporation of New York City.
The ABC was built by Atanasoff and Berry in the basement of the physics building at Iowa State College from 1939 to 1942. The initial funds were released in September, and the 11-tube prototype was first demonstrated in October 1939. A December demonstration prompted a grant for construction of the full-scale machine. The ABC was built and tested over the next two years. A January 15, 1941, story in the Des Moines Register announced the ABC as "an electrical computing machine" with more than 300 vacuum tubes that would "compute complicated algebraic equations" (but gave no precise technical description of the computer). The system weighed more than . It contained approximately of wire, 280 dual-triode vacuum tubes, 31 thyratrons, and was about the size of a desk.
It was not programmable, which distinguishes it from more general machines of the same era, such as Konrad Zuse's 1941 Z3 (or earlier iterations) and the Colossus computers of 1943–1945. Nor did it implement the stored-program architecture, first implemented in the Manchester Baby of 1948, required for fully general-purpose practical computing machines.
thumb|Add-subtract module (reconstructed) from Atanasoff–Berry computer
The machine was, however, the first to implement:
Using vacuum tubes, rather than wheels, ratchets, mechanical switches, or telephone relays, allowing for greater speed than previous computers
Using capacitors for memory, rather than mechanical components, allowing for greater speed and density
The memory of the Atanasoff–Berry computer was a system called regenerative capacitor memory, which consisted of a pair of drums, each containing 1600 capacitors that rotated on a common shaft once per second. The capacitors on each drum were organized into 32 "bands" of 50 (30 active bands and two spares in case a capacitor failed), giving the machine a speed of 30 additions/subtractions per second. Data was represented as 50-bit binary fixed-point numbers. The electronics of the memory and arithmetic units could store and operate on 60 such numbers at a time (3000 bits).
The alternating current power-line frequency of 60 Hz was the primary clock rate for the lowest-level operations.
The arithmetic logic functions were fully electronic, implemented with vacuum tubes. The family of logic gates ranged from inverters to two- and three-input gates. The input and output levels and operating voltages were compatible between the different gates. Each gate consisted of one inverting vacuum-tube amplifier, preceded by a resistor divider input network that defined the logical function. The control logic functions, which only needed to operate once per drum rotation and therefore did not require electronic speed, were electromechanical, implemented with relays.
The ALU operated on only one bit of each number at a time; it kept the carry/borrow bit in a capacitor for use in the next AC cycle.John Gustafson.
"Reconstruction of the Atanasoff-Berry Computer".
Quote: "the total vacuum tube count was very low: about 300 for the entire machine. Much of this economy is the result of operating on only one bit of each number at a time, keeping the carry/borrow bit in a capacitor for use in the next cycle."
Although the Atanasoff–Berry computer was an important step up from earlier calculating machines, it was not able to run entirely automatically through an entire problem. An operator was needed to operate the control switches to set up its functions, much like the electro-mechanical calculators and unit record equipment of the time. Selection of the operation to be performed, reading, writing, converting to or from binary to decimal, or reducing a set of equations was made by front-panel switches and, in some cases, jumpers.
There were two forms of input and output: primary user input and output and an intermediate results output and input. The intermediate results storage allowed operation on problems too large to be handled entirely within the electronic memory. (The largest problem that could be solved without the use of the intermediate output and input was two simultaneous equations, a trivial problem.)
Intermediate results were binary, written onto paper sheets by electrostatically modifying the resistance at 1500 locations to represent 30 of the 50-bit numbers (one equation). Each sheet could be written or read in one second. The reliability of the system was limited to about 1 error in 100,000 calculations by these units, primarily attributed to lack of control of the sheets' material characteristics. In retrospect, a solution could have been to add a parity bit to each number as written. This problem was not solved by the time Atanasoff left the university for war-related work.
Primary user input was decimal, via standard IBM 80-column punched cards, and output was decimal, via a front-panel display.
thumb|Inside display on I-35 rest stop 100 north of Des Moines honoring the ABC Computer
thumb|Outside display on I-35 rest stop 100 north of Des Moines honoring the ABC Computer |
Atanasoff–Berry computer | Function | Function
The ABC was designed for a specific purpose the solution of systems of simultaneous linear equations. It could handle systems with up to 29 equations, a difficult problem for the time. Problems of this scale were becoming common in physics, the department in which John Atanasoff worked. The machine could be fed two linear equations with up to 29 variables and a constant term and eliminate one of the variables. This process would be repeated manually for each of the equations, which would result in a system of equations with one fewer variable. Then the whole process would be repeated to eliminate another variable.
George W. Snedecor, the head of Iowa State's Statistics Department, was very likely the first user of an electronic digital computer to solve real-world mathematics problems. He submitted many of these problems to Atanasoff. |
Atanasoff–Berry computer | Patent dispute | Patent dispute
On June 26, 1947, J. Presper Eckert and John Mauchly were the first to file for patent on a digital computing device (ENIAC), much to the surprise of Atanasoff. The ABC had been examined by John Mauchly in June 1941, and Isaac Auerbach, a former student of Mauchly's, alleged that it influenced his later work on ENIAC, although Mauchly denied this. The ENIAC patent did not issue until 1964, and by 1967 Honeywell sued Sperry Rand in an attempt to break the ENIAC patents, arguing that the ABC constituted prior art. The United States District Court for the District of Minnesota released its judgement on October 19, 1973, finding in Honeywell v. Sperry Rand that the ENIAC patent was a derivative of John Atanasoff's invention.
Campbell-Kelly and Aspray conclude:
The case was legally resolved on October 19, 1973, when U.S. District Judge Earl R. Larson held the ENIAC patent invalid, ruling that the ENIAC derived many basic ideas from the Atanasoff–Berry computer. Judge Larson explicitly stated:
Herman Goldstine, one of the original developers of ENIAC wrote:Herman Goldstine, "The Computer from Pascal to von Neumann", 1972; pp. 125–126. |
Atanasoff–Berry computer | Replica | Replica
The original ABC was eventually dismantled in 1948, when the university converted the basement to classrooms, and all of its pieces except for one memory drum were discarded.
In 1997, a team of researchers led by Delwyn Bluhm and John Gustafson from Ames Laboratory (located on the Iowa State University campus) finished building a working replica of the Atanasoff–Berry computer at a cost of $350,000 (equivalent to $ in ). The replica ABC was on display in the first floor lobby of the Durham Center for Computation and Communication at Iowa State University and was subsequently exhibited at the Computer History Museum. |
Atanasoff–Berry computer | See also | See also
History of computing hardware
List of vacuum-tube computers
Mikhail Kravchuk |
Atanasoff–Berry computer | References | References |
Atanasoff–Berry computer | Bibliography | Bibliography
|
Atanasoff–Berry computer | External links | External links
The Birth of the ABC
Reconstruction of the ABC, 1994-1997
John Gustafson, Reconstruction of the Atanasoff-Berry Computer
The ENIAC patent trial
Honeywell v. Sperry Rand Records, 1846-1973, Charles Babbage Institute, University of Minnesota.
The Atanasoff-Berry Computer In Operation (YouTube)
Category:1940s computers
Category:One-of-a-kind computers
Category:Vacuum tube computers
Category:Computer-related introductions in 1942
Category:Early computers
Category:Iowa State University
Category:Serial computers
Category:Paper data storage |
Atanasoff–Berry computer | Table of Content | short description, Overview, Design and construction, Function, Patent dispute, Replica, See also, References, Bibliography, External links |
Andes | Short description | thumb|"Cono de Arita" in the Puna de Atacama, Salta (Argentina)
thumb|Aconcagua
The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long and wide (widest between 18°S and 20°S latitude) and has an average height of about . The Andes extend from South to North through seven South American countries: Argentina, Chile, Bolivia, Peru, Ecuador, Colombia, and Venezuela.
Along their length, the Andes are split into several ranges, separated by intermediate depressions. The Andes are the location of several high plateaus—some of which host major cities such as Quito, Bogotá, Cali, Arequipa, Medellín, Bucaramanga, Sucre, Mérida, El Alto, and La Paz. The Altiplano Plateau is the world's second highest after the Tibetan Plateau. These ranges are in turn grouped into three major divisions based on climate: the Tropical Andes, the Dry Andes, and the Wet Andes.
The Andes are the highest mountain range outside of Asia. The range's highest peak, Argentina's Aconcagua, rises to an elevation of about above sea level. The peak of Chimborazo in the Ecuadorian Andes is farther from the Earth's center than any other location on the Earth's surface, due to the equatorial bulge resulting from the Earth's rotation. The world's highest volcanoes are in the Andes, including Ojos del Salado on the Chile-Argentina border, which rises to .
The Andes are also part of the American Cordillera, a chain of mountain ranges (cordillera) that consists of an almost continuous sequence of mountain ranges that form the western "backbone" of the Americas and Antarctica. |
Andes | Etymology | Etymology
The etymology of the word Andes has been debated. The majority consensus is that it derives from the Quechua word "east"Teofilo Laime Ajacopa, Diccionario Bilingüe Iskay simipi yuyayk'ancha, La Paz, 2007 (Quechua–Spanish dictionary) as in Antisuyu (Quechua for "east region"), one of the four regions of the Inca Empire.
The term cordillera comes from the Spanish word cordel "rope" and is used as a descriptive name for several contiguous sections of the Andes, as well as the entire Andean range, and the combined mountain chain along the western part of the North and South American continents. |
Andes | Geography | Geography
thumb|Aerial view of Valle Carbajal in the Tierra del Fuego. The Andes range is about wide throughout its length, except in the Bolivian flexure where it is about wide.|alt=Mountains with snowy peaks
The Andes can be divided into three sections:
The Southern Andes in Argentina and Chile, south of Llullaillaco,
The Central Andes in Peru and Bolivia, and
The Northern Andes in Venezuela, Colombia, and Ecuador.
At the northern end of the Andes, the separate Sierra Nevada de Santa Marta range is often, but not always, treated as part of the Northern Andes.
The Leeward Antilles islands Aruba, Bonaire, and Curaçao, which lie in the Caribbean Sea off the coast of Venezuela, were formerly thought to represent the submerged peaks of the extreme northern edge of the Andes range, but ongoing geological studies indicate that such a simplification does not do justice to the complex tectonic boundary between the South American and Caribbean plates. |
Andes | Geology | Geology
The Andes are an orogenic belt of mountains along the Pacific Ring of Fire, a zone of volcanic activity that encompasses the Pacific rim of the Americas as well as the Asia-Pacific region. The Andes are the result of tectonic plate processes extending during the Mesozoic and Tertiary eras, caused by the subduction of oceanic crust beneath the South American Plate as the Nazca Plate and South American Plate converge. These processes were accelerated by the effects of climate. As the uplift of the Andes created a rain shadow on the western fringes of Chile, ocean currents and prevailing winds carried moisture away from the Chilean coast. This caused some areas of the subduction zone to be sediment-starved, which in turn prevented the subducting plate from having a well lubricated surface. These factors increased the rate of contractional coastal uplift in the Andes. The main cause of the rise of the Andes is the contraction of the western rim of the South American Plate due to the subduction of the Nazca Plate and the Antarctic Plate. To the east, the Andes range is bounded by several sedimentary basins, such as the Orinoco Basin, the Amazon Basin, the Madre de Dios Basin, and the Gran Chaco, that separate the Andes from the ancient cratons in eastern South America. In the south, the Andes share a long boundary with the former Patagonia Terrane. To the west, the Andes end at the Pacific Ocean, although the Peru-Chile trench can be considered their ultimate western limit. From a geographical approach, the Andes are considered to have their western boundaries marked by the appearance of coastal lowlands and less-rugged topography. The Andes also contain large quantities of iron ore located in many mountains within the range.
The Andean orogen has a series of bends or oroclines. The Bolivian Orocline is a seaward-concave bending in the coast of South America and the Andes Mountains at about 18° S. At this point, the orientation of the Andes turns from northwest in Peru to south in Chile and Argentina. The Andean segments north and south of the Orocline have been rotated 15° counter-clockwise to 20° clockwise respectively. The Bolivian Orocline area overlaps with the area of the maximum width of the Altiplano Plateau, and according to Isacks (1988) the Orocline is related to crustal shortening. The specific point at 18° S where the coastline bends is known as the Arica Elbow. Further south lies the Maipo Orocline, a more subtle orocline between 30° S and 38°S with a seaward-concave break in the trend at 33° S. Near the southern tip of the Andes lies the Patagonian Orocline. |
Andes | Orogeny | Orogeny
The western rim of the South American Plate has been the place of several pre-Andean orogenies since at least the late Proterozoic and early Paleozoic, when several terranes and microcontinents collided and amalgamated with the ancient cratons of eastern South America, by then the South American part of Gondwana.
The formation of the modern Andes began with the events of the Triassic, when Pangaea began the breakup that resulted in developing several rifts. The development continued through the Jurassic Period. It was during the Cretaceous Period that the Andes began to take their present form, by the uplifting, faulting, and folding of sedimentary and metamorphic rocks of the ancient cratons to the east. The rise of the Andes has not been constant, as different regions have had different degrees of tectonic stress, uplift, and erosion.
Across the Drake Passage lie the mountains of the Antarctic Peninsula south of the Scotia Plate, which appear to be a continuation of the Andes chain.
The far east regions of the Andes experience a series of changes resulting from the Andean orogeny. Parts of the Sunsás Orogen in Amazonian craton disappeared from the surface of the earth, being overridden by the Andes. The Sierras de Córdoba, where the effects of the ancient Pampean orogeny can be observed, owe their modern uplift and relief to the Andean orogeny in the Tertiary. Further south in southern Patagonia, the onset of the Andean orogeny caused the Magallanes Basin to evolve from being an extensional back-arc basin in the Mesozoic to being a contractional foreland basin in the Cenozoic. |
Andes | Seismic activity | Seismic activity
Tectonic forces above the subduction zone along the entire west coast of South America where the Nazca Plate and a part of the Antarctic Plate are sliding beneath the South American Plate continue to produce an ongoing orogenic event resulting in minor to major earthquakes and volcanic eruptions to this day. Many high-magnitude earthquakes have been recorded in the region, such as the 2010 Maule earthquake (M8.8), the 2015 Illapel earthquake (M8.2), and the 1960 Valdivia earthquake (M9.5), which as of 2024 was the strongest ever recorded on seismometers.
The amount, magnitude, and type of seismic activity varies greatly along the subduction zone. These differences are due to a wide range of factors, including friction between the plates, angle of subduction, buoyancy of the subducting plate, rate of subduction, and hydration value of the mantle material. The highest rate of seismic activity is observed in the central portion of the boundary, between 33°S and 35°S. In this area, the angle of subduction is very low, meaning the subducting plate is nearly horizontal. Studies of mantle hydration across the subduction zone have shown a correlation between increased material hydration and lower-magnitude, more-frequent seismic activity. Zones exhibiting dehydration instead are thought to have a higher potential for larger, high-magnitude earthquakes in the future.
The mountain range is also a source of shallow intraplate earthquakes within the South American Plate. The largest such earthquake (as of 2024) struck Peru in 1947 and measured 7.5. In the Peruvian Andes, these earthquakes display normal (1946), strike-slip (1976), and reverse (1969, 1983) mechanisms. The Amazonian Craton is actively underthrusted beneath the sub-Andes region of Peru, producing thrust faults. In Colombia, Ecuador, and Peru, thrust faulting occurs along the sub-Andes due in response to contraction brought on by subduction, while in the high Andes, normal faulting occurs in response to gravitational forces.
In the extreme south, a major transform fault separates Tierra del Fuego from the small Scotia Plate. |
Andes | Volcanism | Volcanism
thumb|upright=1.3|Rift Valley near Quilotoa, Ecuador
thumb|upright|This photo from the ISS shows the high plains of the Andes Mountains in the foreground, with a line of young volcanoes facing the much lower Atacama Desert
The Andes range has many active volcanoes distributed in four volcanic zones separated by areas of inactivity. The Andean volcanism is a result of the subduction of the Nazca Plate and Antarctic Plate underneath the South American Plate. The belt is subdivided into four main volcanic zones that are separated from each other by volcanic gaps. The volcanoes of the belt are diverse in terms of activity style, products, and morphology. Although some differences can be explained by which volcanic zone a volcano belongs to, there are significant differences inside volcanic zones and even between neighboring volcanoes. Despite being a typical location for calc-alkalic and subduction volcanism, the Andean Volcanic Belt has a large range of volcano-tectonic settings, such as rift systems, extensional zones, transpressional faults, subduction of mid-ocean ridges, and seamount chains apart from a large range of crustal thicknesses and magma ascent paths, and different amount of crustal assimilations. |
Andes | Ore deposits and evaporites | Ore deposits and evaporites
The Andes Mountains host large ore and salt deposits, and some of their eastern fold and thrust belts act as traps for commercially exploitable amounts of hydrocarbons. In the forelands of the Atacama Desert, some of the largest porphyry copper mineralizations occur, making Chile and Peru the first- and second-largest exporters of copper in the world. Porphyry copper in the western slopes of the Andes has been generated by hydrothermal fluids (mostly water) during the cooling of plutons or volcanic systems. The porphyry mineralization further benefited from the dry climate that reduced the disturbing actions of meteoric water. The dry climate in the central western Andes has also led to the creation of extensive saltpeter deposits that were extensively mined until the invention of synthetic nitrates. Yet another result of the dry climate are the salars of Atacama and Uyuni, the former being the largest source of lithium and the latter the world's largest reserve of the element. Early Mesozoic and Neogene plutonism in Bolivia's Cordillera Central created the Bolivian tin belt as well as the famous, now mostly depleted, silver deposits of Cerro Rico de Potosí. |
Andes | Climate | Climate
The Andes Mountains is connected connection to the climate of South America, particularly through the hyper-arid conditions of the adjacent Atacama Desert. The Atacama Bench, a prominent low-relief feature along the Pacific seaboard, serves as a key geomorphological record of the long-term interplay between Andean tectonics and Cenozoic climate. While the initial uplift and shortening of the Andes were driven by the subduction of the Nazca Plate beneath the South American Plate, arid climate acted as an important feedback mechanism. Reduced erosion rates in the increasingly arid Atacama region may have effectively stopped tectonic activity in certain parts of the mountain range. This lack of erosion could have facilitated the eastward propagation of deformation, leading to the widening of the Andean orogen over time. Thus, the Atacama Desert and its geological features, like the Atacama Bench, offer critical insights into the coupled evolution of the Andes Mountains and the changing regional climate. |
Andes | History | History
The Andes Mountains, initially inhabited by hunter-gatherers, experienced the development of agriculture and the rise of politically centralized civilizations, which culminated in the establishment of the century-long Inca Empire. This all changed in the 16th century, when the Spanish conquistadors colonized the mountains in advance of the mining economy.
In the tide of anti-imperialist nationalism, the Andes became the scene of a series of independence wars in the 19th century, when rebel forces swept through the region to overthrow Spanish colonial rule. Since then, many former Spanish territories have become five independent Andean states. |
Andes | Climate and hydrology | Climate and hydrology
thumb|Central Andes
thumb|Bolivian Andes
The climate in the Andes varies greatly depending on latitude, altitude, and proximity to the sea. Temperature, atmospheric pressure, and humidity decrease in higher elevations. The southern section is rainy and cool, while the central section is dry. The northern Andes are typically rainy and warm, with an average temperature of in Colombia. The climate is known to change drastically in rather short distances. Rainforests exist just kilometers away from the snow-covered peak of Cotopaxi. The mountains have a large effect on the temperatures of nearby areas. The snow line depends on the location. It is between in the tropical Ecuadorian, Colombian, Venezuelan, and northern Peruvian Andes, rising to in the drier mountains of southern Peru and northern Chile south to about 30°S before descending to on Aconcagua at 32°S, at 40°S, at 50°S, and only in Tierra del Fuego at 55°S; from 50°S, several of the larger glaciers descend to sea level.
The Andes of Chile and Argentina can be divided into two climatic and glaciological zones: the Dry Andes and the Wet Andes. Since the Dry Andes extend from the latitudes of the Atacama Desert to the area of the Maule River, precipitation is more sporadic, and there are strong temperature oscillations. The line of equilibrium may shift drastically over short periods of time, leaving a whole glacier in the ablation area or in the accumulation area.
In the high Andes of Central Chile and Mendoza Province, rock glaciers are larger and more common than glaciers; this is due to the high exposure to solar radiation.Jan-Christoph Otto, Joachim Götz, Markus Keuschnig, Ingo Hartmeyer, Dario Trombotto, and Lothar Schrott (2010). Geomorphological and geophysical investigation of a complex rock glacier system—Morenas Coloradas valley (Cordon del Plata, Mendoza, Argentina) In these regions, glaciers occur typically at higher altitudes than rock glaciers. The lowest active rock glaciers occur at 900 m a.s.l. in Aconcagua.
Though precipitation increases with height, there are semiarid conditions in the nearly highest mountains of the Andes. This dry steppe climate is considered to be typical of the subtropical position at 32–34° S. The valley bottoms have no woods, just dwarf scrub. The largest glaciers, for example the Plomo Glacier and the Horcones Glaciers, do not even reach in length and have only insignificant ice thickness. At glacial times, however, 20,000 years ago, the glaciers were over ten times longer. On the east side of this section of the Mendozina Andes, they flowed down to and on the west side to about above sea level.Kuhle, M. (2011): The High-Glacial (Last Glacial Maximum) Glacier Cover of the Aconcagua Group and Adjacent Massifs in the Mendoza Andes (South America) with a Closer Look at Further Empirical Evidence. Development in Quaternary Science, Vol. 15 (Quaternary Glaciation – Extent and Chronology, A Closer Look, Eds: Ehlers, J.; Gibbard, P.L.; Hughes, P.D.), 735–738. (Elsevier B.V., Amsterdam).Brüggen, J. (1929): Zur Glazialgeologie der chilenischen Anden. Geol. Rundsch. 20, 1–35, Berlin. The massifs of Aconcagua (), Tupungato (), and Nevado Juncal () are tens of kilometres away from each other and were connected by a joint ice stream network. The Andes' dendritic glacier arms, components of valley glaciers, were up to long and over thick, and spanned a vertical distance of . The climatic glacier snowline (ELA) was lowered from to at glacial times.Kuhle, M. (1984): Spuren hocheiszeitlicher Gletscherbedeckung in der Aconcagua-Gruppe (32–33° S). In: Zentralblatt für Geologie und Paläontologie Teil 1 11/12, Verhandlungsblatt des Südamerika-Symposiums 1984 in Bamberg: 1635–1646.Kuhle, M. (1986): Die Vergletscherung Tibets und die Entstehung von Eiszeiten. In: Spektrum der Wissenschaft 9/86: 42–54.Kuhle, M. (1987): Subtropical Mountain- and Highland-Glaciation as Ice Age Triggers and the Waning of the Glacial Periods in the Pleistocene. In: GeoJournal 14 (4); Kluwer, Dordrecht/ Boston/ London: 393–421.Kuhle, M. (1988): Subtropical Mountain- and Highland-Glaciation as Ice Age Triggers and the Waning of the Glacial Periods in the Pleistocene. In: Chinese Translation Bulletin of Glaciology and Geocryology 5 (4): 1–17 (in Chinese language).Kuhle, M. (1989): Ice-Marginal Ramps: An Indicator of Semiarid Piedmont Glaciations. In: GeoJournal 18; Kluwer, Dordrecht/ Boston/ London: 223–238.Kuhle, M. (1990): Ice Marginal Ramps and Alluvial Fans in Semi-Arid Mountains: Convergence and Difference. In: Rachocki, A.H., Church, M. (eds.): Alluvial fans: A field approach. John Wiley & Sons Ltd, Chester-New York-Brisbane-Toronto-Singapore: 55–68.Kuhle, M. (1990): The Probability of Proof in Geomorphology—an Example of the Application of Information Theory to a New Kind of Glacigenic Morphological Type, the Ice-marginal Ramp (Bortensander). In: GeoJournal 21 (3); Kluwer, Dordrecht/ Boston/ London: 195–222.Kuhle, M. (2004): The Last Glacial Maximum (LGM) glacier cover of the Aconcagua group and adjacent massifs in the Mendoza Andes (South America). In: Ehlers, J., Gibbard, P.L. (Eds.), Quaternary Glaciation— Extent and Chronology. Part III: South America, Asia, Africa, Australia, Antarctica. Development in Quaternary Science, vol. 2c. Elsevier B.V., Amsterdam, pp. 75–81. |
Andes | Flora | Flora
thumb|Laguna de Sonso tropical dry forest in Northern Andes
The Andean region cuts across several natural and floristic regions, due to its extension, from Caribbean Venezuela to cold, windy, and wet Cape Horn passing through the hyperarid Atacama Desert. Rainforests and tropical dry forests used to encircle much of the northern Andes but are now greatly diminished, especially in the Chocó and inter-Andean valleys of Colombia. Opposite the humid Andean slopes are the relatively dry Andean slopes in most of western Peru, Chile, and Argentina. Along with several Interandean Valles, they are typically dominated by deciduous woodland, shrub and xeric vegetation, reaching the extreme in the slopes near the virtually lifeless Atacama Desert.
About 30,000 species of vascular plants live in the Andes, with roughly half being endemic to the region, surpassing the diversity of any other hotspot. The small tree Cinchona pubescens, a source of quinine that is used to treat malaria, is found widely in the Andes as far south as Bolivia. Other important crops that originated from the Andes are tobacco and potatoes. The high-altitude Polylepis forests and woodlands are found in the Andean areas of Colombia, Ecuador, Peru, Bolivia, and Chile. These trees, by locals referred to as Queñua, Yagual, and other names, can be found at altitudes of above sea level. It remains unclear if the patchy distribution of these forests and woodlands is natural, or the result of clearing that began during the Incan period. Regardless, in modern times, the clearance has accelerated, and the trees are now considered highly endangered, with some believing that as little as 10% of the original woodland remains. |
Andes | Fauna | Fauna
thumb|A male Andean cock-of-the-rock, a species found in humid Andean forests and the national bird of Peru
thumb|Herds of alpacas near Ausangate mountain
The Andes are rich in fauna: With almost 1,000 species, of which roughly 2/3 are endemic to the region, the Andes are the most important region in the world for amphibians.Tropical Andes – biodiversityhotspots.org The diversity of animals in the Andes is high, with almost 600 species of mammals (13% endemic), more than 1,700 species of birds (about 1/3 endemic), more than 600 species of reptiles (about 45% endemic), and almost 400 species of fish (about 1/3 endemic).
The vicuña and guanaco can be found living in the Altiplano, while the closely related domesticated llama and alpaca are widely kept by locals as pack animals and for their meat and wool. The crepuscular (active during dawn and dusk) chinchillas, two threatened members of the rodent order, inhabit the Andes' alpine regions.Eisenberg, J.F.; & Redford, K.H. (2000). Mammals of the Neotropics, Volume 3: The Central Neotropics: Ecuador, Peru, Bolivia, Brazil. Eisenberg, J.F.; & Redford, K.H. (1992). Mammals of the Neotropics, Volume 2: The Southern Cone: Chile, Argentina, Uruguay, Paraguay. The Andean condor, the largest bird of its kind in the Western Hemisphere, occurs throughout much of the Andes but generally in very low densities.Fjeldsaa, J.; & Krabbe, N. (1990). Birds of the High Andes: A Manual to the Birds of the Temperate Zone of the Andes and Patagonia, South America. Other animals found in the relatively open habitats of the high Andes include the huemul, cougar, foxes in the genus Pseudalopex, and, for birds, certain species of tinamous (notably members of the genus Nothoprocta), Andean goose, giant coot, flamingos (mainly associated with hypersaline lakes), lesser rhea, Andean flicker, diademed sandpiper-plover, miners, sierra-finches and diuca-finches.
Lake Titicaca hosts several endemics, among them the highly endangered Titicaca flightless grebe and Titicaca water frog.Stuart, Hoffmann, Chanson, Cox, Berridge, Ramani and Young, editors (2008). Threatened Amphibians of the World. A few species of hummingbirds, notably some hillstars, can be seen at altitudes above , but far higher diversities can be found at lower altitudes, especially in the humid Andean forests ("cloud forests") growing on slopes in Colombia, Ecuador, Peru, Bolivia, and far northwestern Argentina. These forest-types, which includes the Yungas and parts of the Chocó, are very rich in flora and fauna, although few large mammals exist, exceptions being the threatened mountain tapir, spectacled bear, and yellow-tailed woolly monkey.
Birds of humid Andean forests include mountain toucans, quetzals, and the Andean cock-of-the-rock, while mixed-species flocks dominated by tanagers and furnariids are commonly seen—in contrast to several vocal but typically cryptic species of wrens, tapaculos, and antpittas.
A number of species such as the royal cinclodes and white-browed tit-spinetail are associated with Polylepis, and consequently also threatened. |
Andes | Human activity | Human activity
The Andes Mountains form a north–south axis of cultural influences. A long series of cultural development culminated in the expansion of the Inca civilization and Inca Empire in the central Andes during the 15th century. The Incas formed this civilization through imperialistic militarism as well as careful and meticulous governmental management.D'Altroy, Terence N. The Incas. Blackwell Publishing, 2003 The government sponsored the construction of aqueducts and roads in addition to pre-existing installations. Some of these constructions still exist today.
thumb|Frederic Edwin Church, Heart of the Andes, 1859.
Devastated by European diseases and by civil war, the Incas were defeated in 1532 by an alliance composed of tens of thousands of allies from nations they had subjugated (e.g. Huancas, Chachapoyas, Cañaris) and a small army of 180 Spaniards led by Francisco Pizarro. One of the few Inca sites the Spanish never found in their conquest was Machu Picchu, which lay hidden on a peak on the eastern edge of the Andes where they descend to the Amazon. The main surviving languages of the Andean peoples are those of the Quechua and Aymara language families. Woodbine Parish and Joseph Barclay Pentland surveyed a large part of the Bolivian Andes from 1826 to 1827. |
Andes | Cities | Cities
In modern times, the largest cities in the Andes are Bogotá, with a metropolitan population of over ten million, and Santiago, Medellín, Cali, and Quito. Lima is a coastal city adjacent to the Andes and is the largest city of all Andean countries. It is the seat of the Andean Community of Nations.
La Paz, Bolivia's seat of government, is the highest capital city in the world, at an elevation of approximately . Parts of the La Paz conurbation, including the city of El Alto, extend up to .
Other cities in or near the Andes include Bariloche, Catamarca, Jujuy, Mendoza, Salta, San Juan, Tucumán, and Ushuaia in Argentina; Calama and Rancagua in Chile; Cochabamba, Oruro, Potosí, Sucre, Tarija, and Yacuiba in Bolivia; Arequipa, Cajamarca, Cusco, Huancayo, Huánuco, Huaraz, Juliaca, and Puno in Peru; Ambato, Cuenca, Ibarra, Latacunga, Loja, Riobamba, and Tulcán in Ecuador; Armenia, Cúcuta, Bucaramanga, Duitama, Ibagué, Ipiales, Manizales, Palmira, Pasto, Pereira, Popayán, Rionegro, Sogamoso, Tunja, and Villavicencio in Colombia; and Barquisimeto, La Grita, Mérida, San Cristóbal, Tovar, Trujillo, and Valera in Venezuela. The cities of Caracas, Valencia, and Maracay are in the Venezuelan Coastal Range, which is a debatable extension of the Andes at the northern extremity of South America. |
Andes | Transportation | Transportation
Cities and large towns are connected with asphalt-paved roads, while smaller towns are often connected by dirt roads, which may require a four-wheel-drive vehicle.
The rough terrain has historically put the costs of building highways and railroads that cross the Andes out of reach of most neighboring countries, even with modern civil engineering practices. For example, the main crossover of the Andes between Argentina and Chile is still accomplished through the Paso Internacional Los Libertadores. Only recently have the ends of some highways that came rather close to one another from the east and the west been connected. Much of the transportation of passengers is done via aircraft.
There is one railroad that connects Chile with Peru via the Andes, however, and there are others that make the same connection via southern Bolivia.
There are multiple highways in Bolivia that cross the Andes. Some of these were built during a period of war between Bolivia and Paraguay, in order to transport Bolivian troops and their supplies to the war front in the lowlands of southeastern Bolivia and western Paraguay.
For decades, Chile claimed ownership of land on the eastern side of the Andes. These claims were given up in about 1870 during the War of the Pacific between Chile and the allied Bolivia and Peru, in a diplomatic deal to keep Peru out of the war. The Chilean Army and Chilean Navy defeated the combined forces of Bolivia and Peru, and Chile took over Bolivia's only province on the Pacific Coast, some land from Peru that was returned to Peru decades later. Bolivia has been completely landlocked ever since. It mostly uses seaports in eastern Argentina and Uruguay for international trade because its diplomatic relations with Chile have been suspended since 1978.
Because of the tortuous terrain in places, villages and towns in the mountains—to which travel via motorized vehicles is of little use—are still located in the high Andes of Chile, Bolivia, Peru, and Ecuador. Locally, the relatives of the camel, the llama, and the alpaca continue to carry out important uses as pack animals, but this use has generally diminished in modern times. Donkeys, mules, and horses are also useful. |
Andes | Agriculture | Agriculture
thumb|Peruvian farmers sowing maize and beans
The ancient peoples of the Andes such as the Incas have practiced irrigation techniques for over 6,000 years. Because of the mountain slopes, terracing has been a common practice. Terracing, however, was only extensively employed after Incan imperial expansions to fuel their expanding realm. The potato holds a very important role as an internally consumed staple crop. Maize was also an important crop for these people, and was used for the production of chicha, important to Andean native people. Currently, tobacco, cotton, and coffee are the main export crops. Coca, despite eradication programs in some countries, remains an important crop for legal local use in a mildly stimulating herbal tea, and illegally for the production of cocaine. |
Andes | Irrigation | Irrigation
thumb|Irrigating land in the Peruvian Andes
In unirrigated land, pasture is the most common type of land use. In the rainy season (summer), part of the rangeland is used for cropping (mainly potatoes, barley, broad beans, and wheat).
Irrigation is helpful in advancing the sowing data of the summer crops, which guarantees an early yield in periods of food shortage. Also, by early sowing, maize can be cultivated higher up in the mountains (up to ). In addition, it makes cropping in the dry season (winter) possible and allows the cultivation of frost-resistant vegetable crops like onion and carrot.W. van Immerzeel, 1989. Irrigation and erosion/flood control at high altitudes in the Andes. Published in Annual Report 1989, pp. 8–24, International Institute for Land Reclamation and Improvement, Wageningen, The Netherlands. On line: |
Andes | Mining | Mining
thumb|left|Chilean huasos, 19th century
The Andes rose to fame for their mineral wealth during the Spanish conquest of South America. Although Andean Amerindian peoples crafted ceremonial jewelry of gold and other metals, the mineralizations of the Andes were first mined on a large scale after the Spanish arrival. Potosí in present-day Bolivia and Cerro de Pasco in Peru were among the principal mines of the Spanish Empire in the New World. Río de la Plata and Argentina derive their names from the silver of Potosí.
Currently, mining in the Andes of Chile and Peru places these countries as the first and second major producers of copper in the world. Peru also contains the 4th-largest goldmine in the world: the Yanacocha. The Bolivian Andes principally produce tin, although historically silver mining had a huge impact on the economy of 17th-century Europe.
There is a long history of mining in the Andes, from the Spanish silver mines in Potosí in the 16th century to the vast current porphyry copper deposits of Chuquicamata and Escondida in Chile and Toquepala in Peru. Other metals, including iron, gold, and tin, in addition to non-metallic resources are important. The Andes have a vast supply of lithium; Argentina, Bolivia, and Chile have the three largest reserves in the world respectively. |
Andes | Accion Andina's reforestation plan | Accion Andina's reforestation plan
Depending on the country, this species goes by different names. In Peru, it is known as queñual, queuña, or queñoa; in Bolivia, as kewiña; in Ecuador, as yagual; and in Argentina, tabaquillo. Regardless of the name, Polylepis is a high-Andean genus encompassing up to 45 species of trees and shrubs distributed across the South American Andes, from Venezuela to Patagonia, found up to 5,000 meters above sea level.
In 2000, biologist Constantino Aucca founded Ecoan, an NGO promoting conservation of threatened species and endangered Andean ecosystems. Since then, the organization has reforested 4.5 million plants across 16 protected areas, involving 37 Andean communities in the process.
Aucca's efforts caught the attention of Florent Kaiser, a Franco-German forest engineer. During a visit to Peru in 2018, Aucca invited Kaiser to the Queuña Raymi festival, where Cusco communities engage in queñual reforestation. |
Andes | Peaks | Peaks
This list contains some of the major peaks in the Andes mountain range. The highest peak is Aconcagua of Argentina. |
Andes | Argentina | Argentina
thumb|right|The Aconcagua, Argentina, the highest mountain in the Americas
Aconcagua,
Cerro Bonete,
Galán,
Mercedario,
Pissis, |
Andes | The border between Argentina and Chile | The border between Argentina and Chile
Cerro Bayo,
Cerro Fitz Roy, or 3,405 m, Patagonia, also known as Cerro Chaltén
Cerro Escorial,
Cordón del Azufre,
Falso Azufre,
Incahuasi,
Lastarria,
Llullaillaco,
Maipo,
Marmolejo,
Ojos del Salado,
Olca,
Sierra Nevada de Lagunas Bravas,
Socompa,
Nevado Tres Cruces, (south summit) (III Region)
Tronador,
Tupungato,
Nacimiento,
thumb|Huayna Potosí, Bolivia |
Andes | Bolivia | Bolivia
thumb|Sajama, Bolivia
Janq'u Uma,
Cabaraya,
Chacaltaya,
Chachacomani,
Chaupi Orco,
Huayna Potosí,
Illampu,
Illimani,
Laram Q'awa,
Macizo de Pacuni,
Mururata,
Nevado Anallajsi,
Nevado Charquini,
Nevado Sajama,
Patilla Pata,
Tata Sabaya,
Tunari,
Uturuncu,
Wayna Potosí, |
Andes | Border between Bolivia and Chile | Border between Bolivia and Chile
thumb|Parinacota, Bolivia/Chile
Acotango,
Aucanquilcha,
Michincha,
Iru Phutunqu,
Licancabur,
Olca,
Parinacota,
Paruma,
Pomerape, |
Andes | Chile | Chile
thumb|right|View of Cuernos del Paine in Torres del Paine National Park, Chile
Monte San Valentin,
Cerro Paine Grande,
Cerro Macá, c.
Monte Darwin, c.
Volcan Hudson, c.
Cerro Castillo Dynevor, c.
Mount Tarn, c.
Polleras, c.
Acamarachi, c. |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.