Agrosaurus

Lore & Background

Members of an expedition from the British sloop-of-war HMS Fly supposedly collected two tibiae, a fibula, two foot claws, and some other fragments in 1844 while erecting a beacon on the coast of Cape York, Queensland in Australia. However, the context of the discovery is uncertain, as it is not mentioned in books by expedition naturalist John MacGallivray nor in a 1847 book on the voyage by geologist Joseph Beete-Jukes. The bones were probably instead collected during the autumn of 1834 in the Magnesian Conglomerate of Bristol by Henry Riley and Samuel Stutchbury. The original block was purchased by the British Museum of Natural History in 1879 from Edward Charlesworth and given the inventory number BMNH 49984, but the remains were not studied until 1891, when Harry Govier Seeley named it Agrosaurus macgillivrayi, not giving an etymology.

Reader's Guide

Agrosaurus is significant primarily as a case study in misidentification in paleontology. Originally hailed as the oldest dinosaur from Australia, later research—including preparation of the block in the late 1980s and comparison of the rock matrix—showed that the bones almost certainly came from the Magnesian Conglomerate of Bristol, England, not Australia. The matrix matched English beds where Thecodontosaurus remains have been found, and a jaw of a sphenodont identical to Diphydontosaurus avonis, a reptile common to the Bristol Triassic beds, was extracted from the same matrix. As a result, Agrosaurus is now generally considered a nomen dubium or a junior synonym of Thecodontosaurus. Its legacy lies in illustrating how provenance errors can distort the fossil record; if Agrosaurus is not from Australia, then Rhoetosaurus and Ozraptor, both from the Bajocian (Middle Jurassic), are the oldest known Australian dinosaurs.

Did You Know?

• Agrosaurus was originally believed to be a Triassic prosauropod from Australia, but the material actually appears to come from Thecodontosaurus or a Thecodontosaurus-like animal from Bristol, England.
• The bones were probably collected during the autumn of 1834 in the Magnesian Conglomerate of Bristol by Henry Riley and Samuel Stutchbury, not in Australia.
• A jaw of a sphenodont identical to Diphydontosaurus avonis, a lizard-like reptile common to the Bristol Triassic beds, was extracted from the same matrix as the holotype.
• If Agrosaurus is not from Australia, Rhoetosaurus and Ozraptor, both from the Bajocian (Middle Jurassic), are the oldest known Australian dinosaurs.