A review of Australasian ichthyosaurs

Abstract

Ichthyosaur fossils have been recorded from four landmasses in the Australasian region—Australia, New Zealand, New Caledonia and Timor—and occur in all three systems of the Mesozoic. Most of the remains are non-diagnostic, but at least three genera have been identified: Mixosaurus, from the Middle Triassic of Timor; Shonisaurus, from the Upper Triassic of New Caledonia; and Platypterygius, from the Lower Cretaceous of Australia and New Zealand. Of these, Platypterygius contains the only material that can be diagnosed to species level. However, current taxonomy of the specimens is controversial, with two synonyms, P. australis and P. longmani, persisting in the literature. An examination of cranial traits in the 'quasi-holotype' of P. australis vs P. longmani demonstrates that they represent the same taxon. Thus, P. longmani should be regarded as the junior synonym. A neotype is also here designated for P. australis to replace the original, which is presumed lost.