Sauropodomorph remains were first documented in North America in 1818, when some bones nearly 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, 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
anthracosaurian
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. 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. ==Description==