Anchisaurus is a genus of basalsauropodomorphdinosaur.[1] It lived during the Early JurassicPeriod, and its fossils have been found in the red sandstone of the Upper Portland Formation, Northeastern United States, which was deposited from the Hettangian age into the Sinemurian age, between about 200 and 192 million years ago.[2] Until recently it was classed as a member of Prosauropoda. The genus name Anchisaurus comes from the Greek αγχι (agkhi) anchi-; "near, close" + Greek σαυρος (sauros); "lizard". Anchisaurus was coined as a replacement name for "Amphisaurus", which was itself a replacement name for Hitchcock's "Megadactylus", both of which had already been used for other animals.
Sauropodomorph remains were first documented in North America in 1818, when some bones nearly 1.8m (6ft) in length were uncovered by Mr. Solomon Ellsworth Jr. while excavating a well with gunpowder in East Windsor, Connecticut. At the time of their discovery it was thought that the bones might be those of a human,[3] but the presence of tail vertebrae falsified that idea. They are now recognized as those of an indeterminate sauropodomorph, possibly more closely related to the plateosaurian prosauropods.[4][5]
In 1855, the original type specimen of Anchisaurus polyzelus, AM 41/109, which is housed at the Amherst College Museum of Natural History, was found by William Smith in Springfield, Massachusetts during blasting a well for the waterhouse at the Springfield Armory.[6] Unfortunately, both the East Windsor and Springfield specimens were severely damaged due to the blasting at the construction sites where they were found, and many of the bones were either accidentally thrown away by the workmen or kept by interested onlookers. As a result, these dinosaurs were only known from incomplete remains.
In 1863, the son of the ichnologist Edward Hitchcock, Edward Hitchcock Jr, described the Springfield remains in a supplement to his father's work on fossil footprints, suggesting they could explain a certain mysterious kind of reptile tracks.[6][7] He then contacted the British paleontologist Richard Owen. Owen advised him to name the finds as a new genus. Owen suggested the name Megadactylus, "large finger" in Greek, in reference to the enormous thumb of the animal. Hitchcock Jr himself then chose the specific namepolyzelus, "much sought for" in Greek, referring to the fact that his father had for many years vainly sought to discover the identity of the track-maker.[8]
In 1877, Professor Othniel Charles Marsh had noted that the name Megadactylus had been preoccupied by Megadactylus Fitzinger 1843, a subgenus of the lizard genus Stellio. In 1882, he replaced the name with Amphisaurus, "near saurian", probably referring to Marsh's interpretation of it as intermediate between primitive dinosaurs—at the time the British Palaeosaurus was an example of what was thought to be a primitive dinosaur—and more derived dinosaurs.[9] In 1885, Marsh had discovered that this name also had been preoccupied, by the anthracosaurianAmphisaurus Barkas 1870, and again replaced it by Anchisaurus, with the same meaning.[10]
Meanwhile, nearly complete specimens had been found in Manchester, Connecticut. In 1884, a series of bridges was built over the Hop Creek. Sandstone blocks were sawed out of Wolcott's Quarry north of Buckland Station. On 20 October, an amateur paleontologist, Charles H. Owen, observed that a block had been removed containing the hind part of a skeleton. He warned Marsh who, using T. A. Bostwick as an intermediary, acquired the piece from the quarry owner, Charles O. Wolcott. Marsh tried to secure the front half of the skeleton but it had already been used in a bridge abutment. The specimen, YPM 208, was named Anchisaurus major, "the larger one", by Marsh in 1889.[11] Eventually, when the bridge was demolished in August 1969, John Ostrom would save the front block. Subsequently, two other dinosaur fossils were located in the quarry. Six metres south of the original find a second skeleton was visible in the quarry face. It was removed as a single block and given the inventory number YPM 1883. In Yale, the part containing the skull was split off and became specimen YPM 40313. In 1891, Marsh made Anchisaurus major a separate genus, Ammosaurus, the "sand saurian". In the same publication he named YPM 1883/YPM 40313 as a new species of Anchisaurus, Anchisaurus colurus, "the mangled one".[12] They served as the templates from which O. C. Marsh in 1893 restored the skeleton.[13] The Manchester specimens are now considered conspecific with Anchisaurus polyzelus.[14] The East Windsor and Manchester specimens are housed at the Peabody Museum of Natural History at Yale University.
The type species is Hitchcock's A. polyzelus. Marsh's A. major (also known as Ammosaurus), A. solus, and A. colurus (also known as Yaleosaurus), have since been recognized as synonyms of A. polyzelus, their supposed differences being due to misinterpretation and different stages of growth.[14] In 2015, the ICZN formally made the more complete type specimen of A. colurus the neotype of the genus Anchisaurus and the species A. polyzelus, rendering A. polyzelus and A. colurus objective synonyms (both names being based on exactly the same fossil).[15]
Broom named Gyposaurus capensis in 1911, from bones discovered in South Africa but Peter Galton renamed these Anchisaurus capensis in 1976. This species has since been reclassified again and is probably a juvenile of Massospondylus carinatus. G. sinensis was also referred here, but appears to be a distinct animal.
The Navajo Sandstone of Arizona is the same age as the Portland Formation, and has produced prosauropod remains that have been referred to as Ammosaurus.[16] However, it is possible that these actually belong to the genus Massospondylus, otherwise known only from South Africa.[17]
In the eastern Canadian province of Nova Scotia, scientists have unearthed prosauropods from the McCoy Brook Formation, which is about 200 to 197 million years old, from the Early Jurassic Hettangian stage. The Nova Scotia material provides clues about the diet of these animals. A large number of gastroliths, stones swallowed to grind up plant material in the gut, were found in the abdomen, as well as bone from the skull of a small sphenodont, Clevosaurus. This indicates that these dinosaurs were omnivorous, with a diet mainly consisting of plants but with an occasional supplement of meat.[18] However, these remains have never been fully described or illustrated and were only tentatively referred to Ammosaurus. A further study identified them as a new taxon of sauropodomorph, Fendusaurus eldoni.[19]
Description
Size of Anchisaurus, compared to a human.
Anchisaurus was a rather small dinosaur, with a length of just over 2 meters (6.6ft), which helps explain why it was once mistaken for human bones.[20] It probably weighed around 27 kilograms (60lb). However, Marsh's species A. major (also known as Ammosaurus) was larger, from 2.5 to 4 meters (8ft 2in to 13ft 1in) and some estimates give it a weight of up to 32 kilograms (70lb). Gregory S. Paul estimated its length at 2.2 meters (7.2ft) and its weight at 20 kilograms (44lb) in 2010.[21]
According to the presence of cf. Otozoum tracks on the Connecticut Valley, Anchisaurus could reach even greater sizes.[22]Otozoum tracks were made by a semibipedal to quadrupedal sauropodomorph close to or on the line leading toward eusauropods. Anchisaurus is one of the two sauropodomorphs recognized in the zone. Based on the four known specimens of Anchisaurus, Yates estimated that the animal measured up to 4.9 meters (16ft) in length.[14] This matches well with the estimated average size of the adult Eubrontes track-maker in the Hartford and Deerfield basins. Based on the largest known Eubrontes footprint, exceptionally large individuals of Anchisaurus probably measured up to 6 meters (20ft) in length.[22]
Due to its primitive appearance, Anchisaurus was previously classified as a prosauropod, a member of a group of animals related to or ancestral to the sauropods. Recent investigations show that a group of traditional prosauropods form a monophyletic sister-group to Sauropoda, and that Anchisaurus is instead closer to sauropods.[14]
The family Anchisauridae was first proposed by Othniel Charles Marsh in 1885 and later defined as a clade consisting of Anchisaurus and its nearest relatives. However, it is not clear which other genera are included in the family; many of the dinosaurs once included have since been moved elsewhere, and the group is not used in most current taxonomies.[14]
Right hind foot of Ammosaurus major, now known to have been a synonym of Anchisaurus polyzeus
Fossils of Anchisaurus were originally discovered in the Portland Formation of the Newark Supergroup in the Connecticut River Valley. This formation preserves an arid environment with strong wet and dry seasons, from the Hettangian age into the Sinemurian age, between about 200 and 195 million years ago.[2]
Digesting plant matter is a much more intensive biochemical process than digesting meat. This herbivore swallowed gastroliths (gizzard stones) to help break down the food in its stomach.[1] Herbivorous dinosaurs needed a huge gut. Since this had to be positioned in front of the pelvis, balancing on two legs became increasingly difficult, as dinosaurs became larger and they gradually evolved into the quadrupedal position that characterizes the later sauropods such as Diplodocus.[23] Prosauropods represented a middle phase between the earliest bipedal herbivores and the later giant sauropods. As a prosauropod, Anchisaurus was mostly typical of this group, which flourished briefly during the late Triassic and early Jurassic. Anchisaurus teeth, used to rip food, were shaped like spoons.[1] It had fewer and more widely spaced teeth than true prosauropods, and as Peter Galton and Michael Cluver observed, narrower feet.[20]Anchisaurus would have spent most of its time on four legs but could have reared up on its hind legs to reach higher plants.
As a facultative biped, Anchisaurus had to have multi-purpose front legs. As 'hands', they could be turned inwards and be used for grasping. It had a simple reversible first 'finger', similar to a 'thumb'. As feet, the five toes could be placed flat against the floor and were strong at the ankle. This unspecialized design is typical of the early dinosaurs.
Related Research Articles
Stegosaurus is a genus of herbivorous, four-legged, armored dinosaur from the Late Jurassic, characterized by the distinctive kite-shaped upright plates along their backs and spikes on their tails. Fossils of the genus have been found in the western United States and in Portugal, where they are found in Kimmeridgian- to Tithonian-aged strata, dating to between 155 and 145 million years ago. Of the species that have been classified in the upper Morrison Formation of the western US, only three are universally recognized: S. stenops, S. ungulatus and S. sulcatus. The remains of over 80 individual animals of this genus have been found. Stegosaurus would have lived alongside dinosaurs such as Apatosaurus, Diplodocus, Camarasaurus and Allosaurus, the latter of which may have preyed on it.
Plateosaurus is a genus of plateosaurid dinosaur that lived during the Late Triassic period, around 214 to 204 million years ago, in what is now Central and Northern Europe. Plateosaurus is a basal (early) sauropodomorph dinosaur, a so-called "prosauropod". The type species is Plateosaurus trossingensis; before 2019, that honor was given to Plateosaurus engelhardti, but it was ruled as undiagnostic by the ICZN. Currently, there are three valid species; in addition to P. trossingensis, P. longiceps and P. gracilis are also known. However, others have been assigned in the past, and there is no broad consensus on the species taxonomy of plateosaurid dinosaurs. Similarly, there are a plethora of synonyms at the genus level.
Dryosaurus is a genus of an ornithopod dinosaur that lived in the Late Jurassic period. It was an iguanodont. Fossils have been found in the western United States and were first discovered in the late 19th century. Valdosaurus canaliculatus and Dysalotosaurus lettowvorbecki were both formerly considered to represent species of Dryosaurus.
Thecodontosaurus is a genus of herbivorous basal sauropodomorph dinosaur that lived during the late Triassic period.
Melanorosaurus is a genus of basal sauropodomorph dinosaur that lived during the Late Triassic period. An omnivore from South Africa, it had a large body and sturdy limbs, suggesting it moved quadrupedally. Its limb bones were massive and heavy like the limb bones of true sauropods.
Riojasaurus was a herbivorous sauropodomorph dinosaur named after La Rioja Province in Argentina where it was found in the Los Colorados Formation in the Ischigualasto-Villa Unión Basin by José Bonaparte. It lived during the Late Triassic and grew to about 6.6 metres (22 ft) long. Riojasaurus is the only known riojasaurid to live in South America.
Massospondylus was a genus of sauropodomorph dinosaur from the Early Jurassic. It was described by Sir Richard Owen in 1854 from remains discovered in South Africa, and is thus one of the first dinosaurs to have been named. Fossils have since been found at other locations in South Africa, Lesotho, and Zimbabwe. Material from Arizona's Kayenta Formation, India, and Argentina has been assigned to the genus at various times, but the Arizonan and Argentinian material are now assigned to other genera.
Isanosaurus is an extinct genus of sauropod dinosaur from Thailand. It was originally dated to approximately 210 million years ago during the Late Triassic, which would make it one of the oldest known sauropods. Its age was later considered uncertain, and may be Early Jurassic or even as young as Late Jurassic. The only species is Isanosaurus attavipachi. Though important for the understanding of sauropod origin and early evolution, Isanosaurus is poorly known. Exact relationships to other early sauropods remain unresolved.
Yunnanosaurus is an extinct genus of sauropodomorph dinosaur that lived approximately 199 to 183 million years ago in what is now the Yunnan Province, in China, for which it was named. Yunnanosaurus was a large sized, moderately-built, ground-dwelling, quadrupedal herbivore, that could also walk bipedally, and ranged in size from 7 meters (23 feet) long and 2 m (6.5 ft) high to 4 m (13 ft) high in the largest species.
Camelotia is a genus of sauropodomorph dinosaur from the Late Triassic or Early Jurassic in what is now England. Paleontologists are divided on which family it may belong to; in the past, Camelotia has generally been assigned to the prosauropods, but this group of primitive dinosaurs is in constant flux. The genus is now considered a member of the family Melanorosauridae, which includes the first true giant herbivorous dinosaurs.
Euskelosaurus is a sauropodomorph dinosaur from the Late Triassic of South Africa and Lesotho. Fossils have only been recovered from the lower Elliot Formation in South Africa and Lesotho, and in one locality in Zimbabwe.
Gryponyx is an extinct genus of massopod sauropodomorph known from southern Free State, central South Africa.
Efraasia is a genus of basal sauropodomorph dinosaur. It was a herbivore which lived during the middle Norian stage of the Late Triassic, around 210 million years ago, in what is now Germany. It was named in 1973 after Eberhard Fraas, who during the early twentieth century collected what were the original type specimens.
Nanosaurus is the name given to a genus of neornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic-age. Its fossils are known from the Morrison Formation of the south-western United States. The type and only species, Nanosaurus agilis, was described and named by Othniel Charles Marsh in 1877. The taxon has a complicated taxonomic history, largely the work of Marsh and Peter M. Galton, involving the genera Laosaurus, Hallopus, Drinker, Othnielia, and Othnielosaurus, the latter three now being considered to be synonyms of Nanosaurus. It had historically been classified as a hypsilophodont or fabrosaur, types of generalized small bipedal herbivore, but more recent research has abandoned these groupings as paraphyletic and Nanosaurus is today considered a basal member of Neornithischia.
Pantydraco is a genus of basal sauropodomorph dinosaur from the Late Triassic of the United Kingdom (Wales). It is based on a partial juvenile skeleton once thought to belong to Thecodontosaurus. Only one valid species of Pantydraco is recognised: P. caducus.
Anchisauria is an extinct clade of sauropodomorph dinosaurs that lived from the Late Triassic to the Late Cretaceous. The name Anchisauria was first used Haekel and defined by Galton and Upchurch in the second edition of The Dinosauria. It is a node-based taxon containing the most recent common ancestor of Anchisaurus polyzelus and Melanorosaurus readi, and all its descendants. Galton and Upchurch assigned a family of dinosaurs to the Anchisauria: the Melanorosauridae. The more common prosauropods Plateosaurus and Massospondylus were placed in the sister clade Plateosauria.
The Blackstone Formation is a geologic formation of the Ipswich Coal Measures Group in southeastern Queensland, Australia, dating to the Carnian to Norian stages of the Late Triassic. The shales, siltstones, coal and tuffs were deposited in a lacustrine environment. The Blackstone Formation contains the Denmark Hill Insect Bed.
Stegomosuchus is an extinct genus of small protosuchian crocodyliform. It is known from a single incomplete specimen discovered in the late 19th century in Lower Jurassic rocks of south-central Massachusetts, United States. It was originally thought to be a species of Stegomus, an aetosaur, but was eventually shown to be related to Protosuchus and thus closer to the ancestry of crocodilians. Stegomosuchus is also regarded as a candidate for the maker of at least some of the tracks named Batrachopus in the Connecticut River Valley.
Sarahsaurus is a genus of basal sauropodomorph dinosaur which lived during the Early Jurassic period in what is now northeastern Arizona, United States.
Paleontology in Connecticut refers to paleontological research occurring within or conducted by people from the U.S. state of Connecticut. Apart from its famous dinosaur tracks, the fossil record in Connecticut is relatively sparse. The oldest known fossils in Connecticut date back to the Triassic period. At the time, Pangaea was beginning to divide and local rift valleys became massive lakes. A wide variety of vegetation, invertebrates and reptiles are known from Triassic Connecticut. During the Early Jurassic local dinosaurs left behind an abundance of footprints that would later fossilize.
References
Wikimedia Commons has media related to Anchisaurus.
↑ Galton, Peter (1976). "Prosauropod dinosaurs (Reptilia: Saurischia) of North America". Postilla. 169: 1–98.
↑ Yates, Adam (2004). "Anchisaurus polyzelus (Hitchcock): The smallest known sauropod dinosaur and the evolution of gigantism among sauropodomorph dinosaurs". Postilla. 230: 1–57.
1 2 Hitchcock, Edward (1858). Ichnology of New England. Boston: William White.
↑ Hitchcock, Edward (1841). Final Report on the Geology of Massachusetts. Volume 2. Containing III Scientific Geology. IV Elementary Geology. Amherst and Northampton: J. S. & C. Adams, J. H. Butler.
↑ E. Hitchcock. 1865. Appendix [A]. Bones of Megadactylus polyzelus. Supplement to the Ichnology of New England. A Report to the Government of Massachusetts in 1863. Wright and Potter, Boston 39–40
↑ Marsh, O. C. 1882. "Classification of the Dinosauria". American Journal of Science, Series 3, 23: 81–86
↑ O. C. Marsh. 1885. "Names of extinct reptiles". American Journal of Science29: 169
↑ ICZN, 2015, "Opinion 2361 (Case 3561): Anchisaurus Marsh, 1885 (Dinosauria, Sauropodomorpha): usage conserved by designation of a neotype for its type species Megadactylus polyzelus Hitchcock, 1865", Bulletin of Zoological Nomenclature72(2): 176–177
1 2 "Anchisaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. The Age of Dinosaurs. Publications International, LTD. p. 27. ISBN0-7853-0443-6.
↑ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 163
↑ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p.122. ISBN1-84028-152-9.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
