MEDIA ALERT

January 25, 2007

Ancient Nullarbor megafauna thrived in dry climate

Dr Gavin Prideaux with the skulls of ancient kangaroos found in the Nullarbor fossil caves.

Thylacoleo skeleton lies as it was found on the cave floor.

The article’s authors track the story of the chance discovery of the three caves, the contents of which palaeontologists describe as the find of the century.

Small holes in the surface of the Nullarbor led a team of exploring cavers into a series of caverns containing the remains of an array of now-extinct animals including giant wombats, short-faced kangaroos and thylacines.

Eight of the 23 kangaroo species identified are entirely new to science, including an unusual wallaby with large ‘brow ridges’ and two tree-kangaroos, the modern relatives of which, ironically, now inhabit dense rain forests in tropical Australia and New Guinea.

The caves also yielded the first complete skeleton of the extinct marsupial lion, Thylacoleo carnifex

Fossils from what have been dubbed the Thylacoleo Caves show that the Nullarbor was once home to at least 69 species of mammals, birds and reptiles, including kangaroos ranging from pint-sized bettongs to three metre giants.

Dr Prideaux, lead author of the Nature article, said researchers reconstructed the ancient Nullarbor environment from oxygen and carbon isotopes contained in the enamel of kangaroo and wombat teeth as well as from the modern geographic ranges of species in the fossil fauna still living today.

“Surprisingly, the climate 500,000 years ago was very similar to that of today, although the region must have had substantially more tree cover to support such a high diversity of herbivores,” Dr Prideaux said.

“Some time during the last 400,000 years, the Nullarbor vegetation changed from the fire-sensitive woodland to the shrub-grass mosaic we see today.”

“We think that an increase in wildfires best explains the shift, given that climate change was not a significant factor.”

Dr Prideaux said the study had significant implications for the debate over what finally drove the megafauna to extinction about 40,000 years ago.

The authors argue that if the Nullarbor animals were well adapted to dry conditions for at least 400,000 years before they disappeared, then it is unlikely they succumbed to Ice Age aridity.

“Our work removes another pillar of support from the idea that the megafauna were driven to extinction by climate change, especially given that most of the large species were not Nullarbor specialists – they were widespread across much of Australia,” Dr Prideaux said.

“Whether or not increased landscape burning on the Nullarbor is correlated with the arrival of humans, as previous researchers have shown for other parts of Australia, remains to be determined.”

The discovery of the Thylacoleo Caves and the first complete Thylacoleo skeleton attracted sustained international media interest and sent a shock wave of excitement through the palaeontological community.

Computer generated graphic showing what Thylacoleo may have looked like.