Agrosaurus

Taxobox
name = "Agrosaurus"
regnum = Animalia
phylum = Chordata
classis = Sauropsida
superordo = Dinosauria
ordo = Saurischia
subordo = Sauropodomorpha
genus = "Agrosaurus"
genus_authority=Seeley, 1891
subdivision_ranks=Species
subdivision=
*"A. macgilivrayi" Seeley, 1891 (type)

"Agrosaurus" (Seeley, 1891; (pronEng|ˌægrəˈsɔrəs) meaning 'field lizard', referring to the place where it was supposedly discovered, (Greek "agros" meaning 'field' and "sauros" meaning 'lizard') 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".

Members of an expedition from the British ship HMS "Fly" supposedly collected a tibia, a claw and some other fragments in 1844 from Cape York, Queensland. The original block was purchased by the British Museum of Natural History in 1879, but the remains were not studied until 1891. Harry Seeley identified it in that year. The block was prepared in the late 1980s. Following the preparation, Ralph Molnar (1991) noticed similarities to the prosauropod "Massospondylus". Galton and Cluver (1976) see "Agrosaurus" as close to "Anchisaurus". Vickers-Rich, Rich, McNamara and Milner (1999) equate "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.' Remains of the jaw of a sphenodont identical to "Diphyodontosaurus avonis", a lizard-like reptile common to the Bristol Triassic beds has been extracted. This reinterpretation of "Agrosaurus" as a misidentified British specimen has been accepted in later works.cite book |last=Weishampel |first=David B. |authorlink=David B. Weishampel |coauthors=Barrett, Paul M.; Coria, Rodolfo A.; Le Loueff, Jean; Xu Xing; Zhao Xijin; Sahni, Ashok; Gomani, Elizabeth M.P.; and Noto, Christopher N. |editor=Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.)|title=The Dinosauria |edition=2nd |year= 2004|publisher=University of California Press |location=Berkeley |isbn=0-520-24209-2 |pages=517-606 |chapter=Dinosaur distribution ] cite journal |last=Galton |first=Peter |authorlink=Peter Galton |year=2007 |title=Notes on the remains of archosaurian reptiles, mostly basal sauropodomorph dinosaurs, from the 1834 fissure fill (Rhaetian, Upper Triassic) at Clifton in Bristol, southwest England |journal=Revue de Paléobiologie |volume=26 |issue=2 |pages=505–591]

From the scant remains the living animal would appear to have been about 3 metres long (10 ft), with a typically prosauropodan appearance: bulky body, long neck, small head and clawed feet. 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 "Agrosaurus" is not from Australia, which seems most probable, "Rhoetosaurus" and "Ozraptor", both from the Bajocian (Middle Jurassic) would be the oldest known Australian dinosaurs. Fortunately they are well documented.

See also

* "Thecodontosaurus"
*List of Australian dinosaurs

References

* John A. Long, Dinosaurs of Australia and New Zealand, UNSW Press 1998
* Vickers-Rich, P., T.H. Rich, G.C. McNamara and A. Milner 1999 "Agrosaurus": Australia's Oldest Dinosaur? Records of the Western Australian Museum Suppliment No.57: 191-200

External links

* [http://home.alphalink.com.au/~dannj/agrosaur.htm "Agrosaurus": the Australian Dinosaur that Wasn't]