Dinosaur ankle points to Australia as stomping ground for ceratosaur

THE FOSSILISED ankle bone of a carnivorous dinosaur found on the Victorian coast in 2006 is the first evidence that a major group of dinosaurs called this part of the world home.

Until now, scientists thought the distribution of the ceratosaur group of dinosaurs was limited to western Gondwana - present day South America, Africa, India and Madagascar. However the fossil find in Victoria, outlined in the journal Naturwissenschaften this week, shows that eastern Gondwana - of which Australia was a part - was a melting-pot for dinosaur diversity during the cretaceous period.

''Until now there had been no record [of the ceratosaur group] from Australia so this discovery really plugs one of the biggest gaps in our dinosaur record,'' Museum Victoria palaeontologist Erich Fitzgerald said.

Dr Fitzgerald, the lead author on the paper, said the dinosaur group joins a growing and ''surprisingly varied'' list of predatory dinosaurs found in Australia compared to other southern continents.

''That diversity can perhaps only be explained, given our geographic isolation, by the probability that these predatory dinosaur groups made it to Australia early on in their history before the continents started to split apart.''

Other carnivorous dinosaurs known to have lived in Australia about 100 million to 125 million years ago include tyrannosaurs, spinosaurids and allosaurs. Each group can be traced as far back as 170 million years ago when all the globe's continents were still connected, meaning that dinosaurs could walk freely between them.

Dr Fitzgerald said this was important because it suggested the dinosaurs found in Australia may not have evolved in isolation. Instead they may represent dinosaurs which had evolved much further back in time.

''You could describe Australia as almost being like a Jurassic Park, in terms of its carnivorous dinosaurs because the groups of predatory dinosaurs we have are groups that have their origins in the Jurassic period,'' he said.

The fossilised left ankle bone was found in grey sandstone at San Remo, 87 kilometres south-east of Melbourne. Dr Fitzgerald said this indicated the adult animal had died near water about 125 million years ago, as that type of sandstone was typically found at the bottom of creeks and rivers.

He said features on the ankle bone - measuring six centimetres wide and five centimetres high - showed it belonged to a member of the ceratosaur group, three-toed dinosaurs which would have stood between one and two metres tall.