Agrosaurus (/ˌæɡroʊˈsɔːrəs/; Greek agrosmeaning 'field' and sauros meaning 'lizard', "field lizard") is an extinct genus of thecodontosaurid sauropodomorph probably originating from England that 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 (Avon Fissure Fill?). The type species is Agrosaurus macgillivrayi.
History
Members of an expedition from the British sloop HMS Fly supposedly collected a tibia, a claw and some other fragments in 1844 from Cape York, Queensland in Australia, although the bones were probably instead collected during the autumn of 1834 in the Magnesian Conglomerate of Bristol by Henry Riley and Samuel Stutchbury.[1] The original block was purchased by the British Museum of Natural History in 1879, but the remains were not studied until 1891. Harry Govier Seeley in that year named it Agrosaurus macgillivrayi.[2] The block was prepared in the late 1980s. Following the preparation, Ralph Molnar (1991) noticed similarities to the prosauropod Massospondylus. Galton and Cluver (1976) saw Agrosaurus as close to Anchisaurus. Vickers-Rich, Rich, McNamara and Milner (1999) equated Agrosaurus and Thecodontosaurus antiquus, claiming that the British Museum remains were mislabelled. The difficulty in correctly identifying the source of the fossil lies in the fact that the log of the Fly does not record it. The matrix in which the prosauropod bones were preserved was tested with rocks of similar age in Cape York and Durdham Downs, the latter being beds where Thecodontosaurus remains have been found in the Bristol area of England. The English beds compared most favourably. In fact, as early as 1906 Friedrich von Huene had described the rock matrix as 'extremely reminiscent of the bone breccia at Durdham Downs near Bristol' and had renamed the species Thecodontosaurus macgillivrayi. Remains of the jaw of a sphenodont identical to Diphyodontosaurus avonis, a lizard-like reptile common to the Bristol Triassic beds have been extracted. This reinterpretation of Agrosaurus as a misidentified British specimen has been accepted in later works.[3][4]
From the scant remains the living animal would appear to have been about three metres long (10 ft), with a typical basal sauropodomorph appearance: bulky body, long neck, small head and clawed feet.[citation needed] Like other prosauropods, it was probably equally comfortable on all fours as well as on its elongated hind legs. It was herbivorous or may have been an omnivore.
The name Agrosaurus is now generally considered to be a nomen dubium or a junior synonym of Thecodontosaurus. If Agrosaurusis not from Australia, which seems most probable, Rhoetosaurus and Ozraptor, both from the Bajocian (Middle Jurassic) would be the oldest known Australian dinosaurs. They are well documented.
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