Anchisaurus

Anchisaurus is a genus of basal sauropodomorph dinosaur.[1] It lived during the Early Jurassic Period, and its fossils have been found in the red sandstone of the Portland Formation, which was deposited from the Hettangian age into the Sinemurian age, between about 200 and 195 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.

Anchisaurus
Temporal range: Early Jurassic, 200–195 Ma
Anchisaurus NT
Life restoration
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Sauropodomorpha
Clade: Sauropodiformes
Clade: Anchisauria
Genus: Anchisaurus
Marsh, 1885
Species:
A. polyzelus
Binomial name
Anchisaurus polyzelus
(Hitchcock, 1865)
Synonyms
  • Megadactylus polyzelus
    Hitchcock, 1865 (preoccupied)
  • Amphisaurus polyzelus
    (Hitchcock, 1865) (preoccupied)
  • Anchisaurus major
    Marsh, 1889
  • Ammosaurus major
    (Marsh, 1889)
  • Anchisaurus colurus
    Marsh, 1891
  • Yaleosaurus colurus
    (Marsh, 1891)
  • Anchisaurus solus
    Marsh, 1892

Description

Anchisaurus SIZE
Size of Anchisaurus, compared to a human.

Anchisaurus was a rather small dinosaur, with a length of just over 2 metres (6.6 ft), which helps explain why it was once mistaken for human bones.[3] It probably weighed around 27 kilograms (60 lb). However, Marsh's species A. major (also known as Ammosaurus) was larger, from 2.5 to 4 metres (8 ft 2 in to 13 ft 1 in) and some estimates give it a weight of up to 70 pounds (32 kg). Gregory S. Paul estimated its length at 2.2 meters and its weight at 20 kg in 2010.[4] According to the presence of cf Otozum tracks on the Connecticut Valley the size of this animal can be even bigger.[5] Otozoum tracks were made by a semibipedal to quadrupedal sauropodomorph close to or on the line leading toward eusauropods. Anchisaurus is one of the 2 Sauropodomorphs recognised in the zone. Based on the four known specimens of Anchisaurus, Yates[6] estimated that this animal ranged up to 4.9 meters in length. 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,[7] exceptionally large individuals of Anchisaurus probably ranged up to 6.0 meters in length (0.442 m 13.5 ¼ 6.0 m).

Discovery and naming

Large marsh anchisaurus
Anchisaurus skeleton restoration by O.C. Marsh.

Sauropodomorph remains were first documented in North America in 1818, when some bones 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,[8] 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.[9][10]

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.[11] 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.[11][12] 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 name polyzelus, "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.[13]

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.[14] In 1885, Marsh had discovered that this name also had been preoccupied, by the athracosaurian Amphisaurus Barkas 1870, and again replaced it by Anchisaurus, with the same meaning.[15]

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.[16] 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".[17] They served as the templates from which O.C. Marsh in 1893 restored the skeleton.[18] The Manchester specimens are now considered conspecific with Anchisaurus polyzelus.[19] 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.[19] 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).[20]

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.[21] However, it is possible that these actually belong to the genus Massospondylus, otherwise known only from South Africa.[22]

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.[23] 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.[24]

Classification

Anchisaurus2
Restoration by Lancelot Speed from 1905

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.[19]

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.[19]

Paleobiology

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.[25] 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.[3] 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.

References

  1. ^ a b c Gaines, Richard M. (2001). Coelophysis. ABDO Publishing Company. p. 14. ISBN 1-57765-488-9.
  2. ^ a b Olsen, P.E. (2002). STRATIGRAPHY AND AGE OF THE EARLY JURASSIC PORTLAND FORMATION OF CONNECTICUT AND MASSACHUSETTS: A CONTRIBUTION TO THE TIME SCALE OF THE EARLY JURASSIC. Session No. 26 Studies of Depositional Systems and Sedimentary Rocks: In Honor of Edward Scudder Belt. 37th Annual Meeting (March 25–27, 2002).
  3. ^ a b "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. ISBN 0-7853-0443-6.
  4. ^ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 163
  5. ^ Robert E. Weems (2019): Evidence for Bipedal Prosauropods as the Likely Eubrontes Track-Makers, Ichnos, DOI: 10.1080/10420940.2018.1532902
  6. ^ Yates, A. 2010. A revision of the problematic sauropodomorph dinosaurs from Manchester, Connecticut and the status of Anchisaurus Marsh. Palaeontology 53(4):739–752
  7. ^ Weems, R. 1992. A re-evaluation of the taxonomy of Newark Supergroup Saurischian dinosaur tracks, using extensive statistical data from a recently exposed track site near Culpeper, Virginia. In Sweet, P.(ed.), 26th forum on the geology of industrial minerals. Virginia Division of Mineral Resources Publication 119:113–128
  8. ^ Smith, Nathan (1820). "Fossil bones found in red sandstones". American Journal of Science. 2: 146–147.
  9. ^ Galton, Peter (1976). "Prosauropod dinosaurs (Reptilia: Saurischia) of North America". Postilla. 169: 1–98.
  10. ^ Yates, Adam (2004). "Anchisaurus polyzelus (Hitchcock): The smallest known sauropod dinosaur and the evolution of gigantism among sauropodomorph dinosaurs". Postilla. 230: 1–57.
  11. ^ a b Hitchcock, Edward (1858). Ichnology of New England. Boston: William White.
  12. ^ 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.
  13. ^ 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
  14. ^ Marsh, O.C. 1882. "Classification of the Dinosauria". American Journal of Science, Series 3, 23: 81–86
  15. ^ O.C. Marsh. 1885. "Names of extinct reptiles". American Journal of Science 29: 169
  16. ^ Marsh, O.C. (1889). "Notice of New American dinosauria". American Journal of Science. 37 (220): 331–336. doi:10.2475/ajs.s3-37.220.331.
  17. ^ O.C. Marsh. 1891. "Notice of new vertebrate fossils". The American Journal of Science, series 3 42: 265-269
  18. ^ Marsh, O.C. (1893). "Restoration of Anchisaurus". American Journal of Science. 45 (266): 169–170. doi:10.2475/ajs.s3-45.266.169.
  19. ^ a b c d Yates, Adam M. (2010). "A revision of the problematic sauropodomorph dinosaurs from Manchester, Connecticut and the status of Anchisaurus Marsh". Palaeontology. 53 (4): 739–752. doi:10.1111/j.1475-4983.2010.00952.x.
  20. ^ 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 Nomenclature 72(2): 176-177
  21. ^ Galton, P.M. (1971).
  22. ^ Galton, P.M., Upchurch, P. (2004).
  23. ^ Shubin, N.H. et al. (1994).
  24. ^ Fedak, T.J. (2007).
  25. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 122. ISBN 1-84028-152-9.
1885 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1885.

1891 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1891.

Anchisauria

The Anchisauria were a clade of sauropodomorph dinosaurs that lived during the Late Triassic and Early Jurassic. The name Anchisauria was first used by Galton and Upchurch in the second edition of The Dinosauria. Galton and Upchurch assigned two families of dinosaurs to the Anchisauria: the Anchisauridae and the Melanorosauridae. The more common prosauropods Plateosaurus and Massospondylus were placed in the sister clade Plateosauria.

However, recent research indicates that Anchisaurus is closer to sauropods than traditional prosauropods; thus, Anchisauria would also include Sauropoda.The following cladogram simplified after an analysis presented by Blair McPhee and colleagues in 2014.

Averostra

Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.

Avetheropoda

Avetheropoda, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.

Chuxiongosaurus

Chuxiongosaurus is a genus of basal sauropodomorph dinosaur which lived during the Early Jurassic Period. Fossils of this genus have been found in the Lower Lufeng Formation, Yunnan Province, southern China. Identified from the holotype CMY LT9401 a nearly complete skull (including a lower jaw) with some similarities to Thecodontosaurus, it was described as the "first basal sauropod dinosaur from the Early Jurassic of China," more basal than Anchisaurus. It was named by Lü Junchang, Yoshitsugu Kobayashi, Li Tianguang and Zhong Shimin in 2010, and the type species is Chuxiongosaurus lufengensis.

Dinosaur classification

Dinosaur classification began in 1842 when Sir Richard Owen placed Iguanodon, Megalosaurus, and Hylaeosaurus in "a distinct tribe or suborder of Saurian Reptiles, for which I would propose the name of Dinosauria." In 1887 and 1888 Harry Seeley divided dinosaurs into the two orders Saurischia and Ornithischia, based on their hip structure. These divisions have proved remarkably enduring, even through several seismic changes in the taxonomy of dinosaurs.

The largest change was prompted by entomologist Willi Hennig's work in the 1950s, which evolved into modern cladistics. For specimens known only from fossils, the rigorous analysis of characters to determine evolutionary relationships between different groups of animals (clades) proved incredibly useful. When computer-based analysis using cladistics came into its own in the 1990s, paleontologists became among the first zoologists to almost wholeheartedly adopt the system. Progressive scrutiny and work upon dinosaurian interrelationships, with the aid of new discoveries that have shed light on previously uncertain relationships between taxa, have begun to yield a stabilizing classification since the mid-2000s. While cladistics is the predominant classificatory system among paleontology professionals, the Linnean system is still in use, especially in works intended for popular distribution.

Gryponyx

Gryponyx (meaning "hooked-claw") is an extinct genus of massopod sauropodomorph known from southern Free State, central South Africa.

Gyposaurus

Gyposaurus (meaning "vulture lizard", referring to the outdated hypothesis that prosauropods were carnivores) is a genus of basal sauropodomorph dinosaur from the early Jurassic of South Africa. It is usually considered to represent juveniles of other prosauropods, but "G." sinensis is regarded as a possibly valid species in recent reviews of the prosauropods (Galton and Upchurch, 2004).

Leonerasaurus

Leonerasaurus is a basal genus of sauropodomorph dinosaur. Currently, there is only one species known, named L. taquetrensis by Diego Pol, Alberto Garrido and Ignacio A. Cerda in 2011. The fossil, an incomplete subadult individual, was found in the Las Leoneras Formation in Argentina. This formation is probably Early Jurassic in age. Leonerasaurus was a small non-sauropod sauropodomorph, showing an unusual combination of basal and derived characters. This indicates that the evolution of early sauropodomorphs witnessed a great degree of convergent evolution.

List of dinosaur genera

This list of dinosaurs is a comprehensive listing of all genera that have ever been included in the superorder Dinosauria, excluding class Aves (birds, both living and those known only from fossils) and purely vernacular terms.

The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (nomen dubium), or were not formally published (nomen nudum), as well as junior synonyms of more established names, and genera that are no longer considered dinosaurs. Many listed names have been reclassified as everything from birds to crocodilians to petrified wood. The list contains 1559 names, of which approximately 1192 are considered either valid dinosaur genera or nomina dubia.

List of the prehistoric life of Connecticut

This list of the prehistoric life of Connecticut contains the various prehistoric life-forms whose fossilized remains have been reported from within the US state of Connecticut.

Massospondylidae

Massospondylidae is a family of early massopod dinosaurs that existed in Asia, Africa, South America and Antarctica during the Late Triassic to the Early Jurassic periods. Several dinosaurs have been classified as massospondylids over the years. The largest cladistic analysis of early sauropodomorphs, which was presented by Apaldetti and colleagues in November 2011, found Adeopapposaurus, Coloradisaurus, Glacialisaurus, Massospondylus, Leyesaurus and Lufengosaurus to be massospondylids. This result supports many previous analyses that tested fewer taxa. However, this analysis found the two recently described North American massopods, Sarahsaurus and Seitaad, and the South African Ignavusaurus to nest outside Massospondylidae, as opposed to some provisional proposals. Earlier in 2011, Pradhania, a sauropodomorph from India, was tested for the first time in a large cladistic analysis and was found to be a relatively basal massospondylid. Mussaurus and Xixiposaurus may also be included within Massospondylidae. In 2019, a specimen previously assigned to Massospondylus from South Africa was re-examined and found to belong to a separate genus that was named Ngwevu.

Mussaurus

Mussaurus (meaning "mouse lizard") is a genus of herbivorous sauropodomorph dinosaur that lived in southern Argentina during the Late Triassic, about 215 million years ago. It receives its name from the small size of the skeletons of juvenile and infant individuals, which were once the only known specimens of the genus. However, since Mussaurus is now known from adult specimens, the name is something of a misnomer; adults possibly reached 6 metres (20 ft) in length and weighed more than 1,000 kilograms (2,200 lb). Mussaurus possesses anatomical features suggesting a close, possibly transitional evolutionary relationship with true sauropods.

Orionides

Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.

Paleontology in Connecticut

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.

The first scientifically verified dinosaur bones discovered in North America were uncovered during the 1818 excavation of a well in Connecticut. Other notable finds include the aetosaur Stegomus, the phytosaur Clepsysaurus, and the prosauropod dinosaur Anchisaurus. The Jurassic dinosaur track Eubrontes giganteus is the Connecticut state fossil.

Pulanesaura

Pulanesaura is an extinct genus of basal sauropod known from the Early Jurassic (late Hettangian to Sinemurian) Upper Elliot Formation of the Free State, South Africa. It contains a single species, Pulanesaura eocollum, known from partial remains of at least two subadult to adult individuals.

When Dinosaurs Roamed America

When Dinosaurs Roamed America (shortened to When Dinosaurs Roamed outside of the U.S.) is a two-hour American television program (produced in the style of a traditional nature documentary) that first aired on the Discovery Channel on July 15, 2001. The show features the reign of the dinosaurs in America over the course of more than 160 million years, through five different segments, each with their own variety of flora and fauna. Unlike Walking with Dinosaurs, the show's creatures are almost entirely composed of computer-generated imagery, and is also one of the first documentaries to depict dromaeosaurs and therizinosaurs with nearly full coats of feathers.

When Dinosaurs Roamed America premiered to 5 million viewers and was released on VHS and DVD a few months after its initial airing. Dinosaur Planet, which aired in December 2003, followed the success of the 2001 program using the same cast, crew, and techniques as its predecessor.

Yunnanosaurus

Yunnanosaurus ( YOO-nan-o-SAWR-əs) is an extinct genus of sauropodomorph dinosaur that lived approximately 201 to 168 million years ago in what is now the Yunnan Province, in China. 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.

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