Australia: The Land Where Time Began

A biography of the Australian continent 

Lower Cretaceous Ichthyosaurs

In the Early Cretaceous of Australia Ichthyosaurs, fast pursuit predators, were a dominant component of the vertebrate assemblages, their remains being very common in deposits from this age. They have been found in the Birdrong Sandstone, Western Australia, of the Hauterivian-Barremian, the Bulldog Shale, South Australia, from the Aptian, the Darwin formation, Northern Territory. They are most prolific in the Toolebuc Formation and Allaru Mudstone (Rolling Downs Group) in Queensland. According to the authors¹ much of this fossil material, and possibly all of it, can be assigned to a single genus Platypterygius, a cosmopolitan opthalmosaurid that during the Cretaceous was the most widespread genus. There are hundreds of known skulls and skeletons of the Australian species Platypterygius australis. This Australian species had very large triangular pectoral fins that had up to 9 rows of tightly fitting finger bones. It has been suggested it had a shark-like swimming motion propelled by a powerful propulsive tail fin and is believed to have had a highly maneuverable lifestyle as a pursuit predator. In fossils of this species that have been found with what is believed to be associated gut contents show that it fed on small fish, hatchling turtles and cephalopods. It also had the remains of birds that have been suggested to have been eaten as scavenged carcasses.

With the exception of a fragmentary fossil from the Birdrong Sandstone of Western Australia that has a humerus structure that is slightly different, suggesting it might be of a different species, all the remains of Platypterygius appear to be virtually indistinguishable from each other.

Sources & Further reading

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