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Wednesday, 26 July 2006

A team led by University of Adelaide palaeontologist Dr Benjamin Kear has identified two new species of ancient marine reptiles that swam the shallow waters of an inland sea in Australia 115 million years ago.

Umoonasaurus and Opallionectes belonged to a group of animals called plesiosaurs, long-necked marine reptiles resembling the popular image of the Loch Ness monster, that lived during the time of the dinosaurs.

Dr Kear and his colleagues from the School of Earth and Environmental Sciences and the South Australian Museum identified the new species based on opalised fossils of 30 individuals found in old collections and recent excavations.

The team's findings were recently published in both the international journal Palaeontology, and the online edition of Biology Letters, a periodical published by the prestigious Royal Society of London.

Umoonasaurus was a rhomaleosaurid - a kind of plesiosaur that was the "killer whale equivalent of the Jurassic," according to Dr Kear. Distinguished by its relatively small size (around 2.4 metres) and three crest-like ridges on its skull, Umoonasaurus was also a "Cretaceous living fossil" outliving its giant predatory relatives by more than 100 million years.

"Imagine a compact body with four flippers, a reasonably long neck, small head and short tail - much like a reptilian seal."

The team named the reptile after Umoona, the Aboriginal name for the Coober Pedy region where the most complete skeletons have been found.

Opallionectes was also a plesiosaur but much larger - about six metres long with masses of fine, needle-like teeth for trapping small fish and squid. Its name means "the opal swimmer from Andamooka".

Both creatures lived in a freezing polar sea that covered what is now Australia 115 million years ago, when the continent was located much closer to Antarctica.

Dr Kear, an Australian Research Council Postdoctoral Fellow, identified the ancient aquatic reptiles with fellow team members Natalie Schroeder and Dr Michael Lee, from the School of Earth and Environmental Sciences. All three work out of the South Australian Museum.