Anchisaurus

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

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. 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. 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.

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. 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.

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. 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". They served as the templates from which O.C. Marsh in 1893 restored the skeleton. The Manchester specimens are now considered conspecific with *Anchisaurus polyzelus*. 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. 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).

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

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. 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*.