Carnivorous bilby fossil unearthed

An ancient predatory bilby has been discovered by Australian scientists.

AUSTRALIA'S BILBIES AND BANDICOOTS  are gentle little marsupials. But the discovery of a 20-million-year-old skull of a carnivorous marsupial shows they had a fearsome ancestor.

The skull was unearthed at the Riversleigh World Heritage Area fossil site in northern Queensland. Based on a study of its features, palaeontologist Kenny Travoullion from the University of New South Wales (UNSW) and his colleagues conclude that it was an ancestor of modern bilbies and other bandicoots and represents a new species. They have dubbed it Galadi speciosus - Galadi from the local Wanyi Aboriginal word meaning bandicoot or possum, speciosus in latin meaning "beautiful in appearance", in reference to its excellent preservation 

Kenny and colleagues describe the powerfully built, short-headed animal as the pit-bull of the bandicoot world. "It was a slasher and a killer - there's no doubt about that," adds Mike Archer, a palaeontologist at UNSW who wasn't involved in the study.

This ancestral bandicoot would have weighed between 800 g and 1kg - almost half the size of a bilby. In some ways its skull looks like that of modern carnivorous marsupials, like quolls, so the team thinks it probably hunted similar prey. "It would have probably eaten small possums, small bandicoots, small birds, lizards, frogs and large insects," Kenny says.

This isn't the only ferocious bandicoot ancestor to be unearthed at Riversleigh. In July, Kenny and colleagues reported finding an 18-million-year-old fossilised bandicoot with large canines. At the time, it was reported as a sabre-toothed bandicoot, but the canines are a little small for this title, Kenny admits. The skull is still encased in limestone, and it will be a few months before it can be fully studied,

Piecing together ancient Australia

It's not clear why the ancient predatory and carnivorous bandicoots died out. But a period of major climate change, which made Australia drier, started about 15 million years ago. It was then that the rainforest homes of these ancestral bandicoots diminished.

"This was a time of massive change not just here but all around the world," says Mike. "It's also the time when the ancestors of human beings began to take a look at the grasslands of Africa and wonder if that wasn't a better place to be."

This new work is crucial for helping to piece together what happened in Australia, he says. "We're not surprised to see profound changes of this kind happening in Australia, but we haven't understood them before. We didn't have the fossil record that told us what happened."

The work on Galadi speciosus will be published in the Journal of Vertebrate Palaeontology.