Australia: The Land Where Time Began

A biography of the Australian continent 

Triassic Early Archosaurs of Australia

It was during the Triassic that archosauromorphs - that includes dinosaurs, pterosaurs, crocodilians and birds - became globally distributed, and in many continental faunas they were the top predators. Archosauromorphs have been found in deposits such as the Arcadia Formation and the Knocklofty Formation in the Tasmania Basin that is of Induan-Olenekian age. Kalisuchus rewanensis, of which a number of fragmentary bones have been recovered from the Arcadia Formation, such as skull components, vertebrae, elements of the limb and girdle. From the Knocklofty Formation an almost complete skeleton of Tasmaniosaurus triassicus has been recovered. Allied with the Proterosuchidae, Kalisuchus, and Tasmaniosaurus, the family that is known best from Russia, South Africa, India and China that is comprised of primitive archosauromorphs that grew up to 3 m in length. According to the authors¹ Proterosuchids are believed to have been crocodile-like predators that were semiaquatic, feeding on fish, small amphibians and reptiles. An indication of their possible prey is seen in the presence of a small temnospondyl associated with the body cavity of Tasmaniosaurus, possibly being the animal's last meal.

The authors¹ have pointed out a number of distinctive proterosuchian features, such as teeth set in shallow sockets that are within a continuous groove, a neck that was long and ankle joints that were crocodile-like are present in the skeleton of Kalisuchus. There are about 16 teeth in the long curved snout of Tasmaniosaurus, and as in proterosuchians such as Proterosuchus, vertebral centra that are characteristic of large aquatic Proterosuchians from South Africa and China. In the Bulgo Sandstone, Narrabeen Group, of Olenekian age, at Long Reef in northern suburban Sydney, proterosuchian vertebrae have been found that are up to 150 mm in height. the authors¹ suggest that it is shown by these remains that more archosauromorph taxa are still to be discovered, though these remains are non-diagnostic.

Sources & Further reading

1. Kear, B.P. & Hamilton-Bruce, R.J., 2011, Dinosaurs in Australia, Mesozoic life from the southern continent, CSIRO Publishing