The ancient koala discovered - with dimples!

A prehistoric species of koala has been discovered by experts studying fossils in an Australian museum.

The team noticed that the fossilised cheekbones at the Western Australian Museum were different to those of modern koalas because they had distinct dimple-like grooves.

They think the species vanished around 28,000 years ago after change in rainfall meant eucalyptus forests virtually disappeared - the main habitat and food for koalas.

It's big news because koalas are commonly found along Australia's east coast, but this is the first new koala species identified from Western Australia.

Fossils from more than a dozen cave sites show that this new species was once living across southern Western Australia.

The newly identified koala species has been given the latin name Phascolarctos sulcomaxilliaris.

Fossils like this have been found for more than a century but it had been assumed that they were Phascolarctos cinereus, the same species still found along the east-coast.

A study was led by Dr Kenny Travouillon, Curator of Mammals at the Western Australian Museum, after it was noticed that one of the fossils "displayed characteristics we don't see in modern koalas, which prompted further investigation."

Researchers did super detailed inspections of 98 bones from fossils in the Museum's collection, and found some major differences between the species.

Dr Travouillon said the deep grooves in the cheekbones suggest the animal may have had "unusually large, mobile lips, possibly for manipulating eucalyptus leaves, or maybe to flare its nostrils to enhance its sense of smell and detect food from greater distances".

The dimpled koala might have also spent less time chewing its food than the modern species.

That's because their wider teeth and different jaw angle allowed more efficient chewing.

But although they might have had some advantages when it came to eating, they could have been less skilled in other areas.

The team think that the skeleton of the newly identified koala species suggests that they were "less agile than modern koalas and may have spent less time moving between trees".

Dr Travouillon also said the dimpled koala may have had even less brain power than its east-coast cousin, which has one of the smallest brain-to-body ratios among mammals.

"Koalas are not famous for being smart, but these ones probably were not as smart again," he added.