|Holotype specimen of Agrosaurus macgillivrayi|
| †Agrosaurus macgillivrayi|
Agrosaurus, meaning 'field lizard', referring to the place where it was supposedly discovered, is the name given to the remains of what was originally believed to be a Triassic prosauropod from Australia. Agrosaurus would thus be the oldest dinosaur from that country. However, this appears to have been an error, and the material actually appears to come from Thecodontosaurus or a Thecodontosaurus-like animal from Bristol, England. The type species is Agrosaurus macgillivrayi. Agrosaurus was first discovered in Australia. The information on this dinosaur is very inconclusive due to a major error in which the fossils for this, already named dinosaur, is thought to be actually from a Thecodontosaurus, or a creature from its family. Theocodotosaurus was a newer member of the sauropdomorph group, which did have a lot of common with the Agrosaurus.
There has not been a full fossil body found either. Its rumored that in 1844, a few members of the British ship HMS Fly found and collected a claw, a tibia, and a few other low profile fossils. The fossils were purchased by the British Museum of Natural History, but not studied until 1891.
In 1981 the fossil was being prepared by Harry Seeley identified the dinosaur. In 1991 a man named Ralph Molnar mentioned the Agrosaurus and the Massospondylus were very simalar. Not only that, but also the Anchisaurus as well. From the scant remains the living animal would appear to have been about 3 metres(9 ft) long.