Sauropodomorph remains were first documented in North America in 1818, when some bones nearly 1.8 m (6 ft) in length were uncovered by Mr. Solomon Ellsworth Jr. while excavating a well with gunpowder in East Windsor, Connecticut.

[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.

Owen suggested the name Megadactylus, "large finger" in Greek, in reference to the enormous thumb of the animal.

On 20 October, an amateur paleontologist, Charles H. Owen, observed that a block had been removed containing the hind part of a skeleton.

[14] The East Windsor and Manchester specimens are housed at the Peabody Museum of Natural History at Yale University.

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.

[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.

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.

[19] Anchisaurus was a rather small dinosaur, with a length of just over 2 meters (6.6 ft), which helps explain why it was once mistaken for human bones.

Based on the four known specimens of Anchisaurus, Yates estimated that the animal measured up to 4.9 meters (16 ft) in length.

Based on the largest known Eubrontes footprint, exceptionally large individuals of Anchisaurus probably measured up to 6 meters (20 ft) 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.

[14] Fossils of Anchisaurus were originally discovered in the Portland Formation of the Newark Supergroup in the Connecticut River Valley.

[1] It had fewer and more widely spaced teeth than true prosauropods, and as Peter Galton and Michael Cluver observed, narrower feet.