Partial to escargot? This 15 million-year-old Aussie marsupial snacked on snails

An artist's impression of a Malleodectid crushing a snail in its teeth. Photo: Peter Schouten

Queensland's 24 million-year-old Riversleigh World Heritage fossil deposits have proffered some stupefying discoveries of extinct animals over the years.

There's been the 'fangaroo', a tusked kangaroo; tree-climbing crocodiles known as 'drop crocs', and the enormous 'demon duck of doom'.

Now we can add to that list of oddities a marsupial that feasted on snails.

Christened Malleodectides - or "wondrous hammer biter" - the furry creature was about the size of a ferret and had massive premolars (the teeth between incisors and molars) made for crunching and digesting whole snails.

It was likely related to other native carnivorous marsupials including the extinct Tasmanian Tiger, the endangered Tasmanian Devil, and the numbat.

Researchers had uncovered bits and pieces of Malleodectids before now, but didn't realise they were looking at an entirely new family until they discovered a 15 million-year-old skull from a young specimen, encased in the cave's limestone floor.

Its diet of escargot is believed to be unique among mammals.

"Malleodectes mirabilis was a bizarre mammal, as strange in its own way as a koala or kangaroo," the study's lead author, Professor Mike Archer from the University of NSW, said.

"Its most striking feature was a huge, extremely powerful, hammer-like premolar that would have been able to crack and then crush the strongest snail shells in the forest."

The young specimen was teething at the time it died. It still had its baby teeth; its adult teeth were beginning to emerge from its jaw.

The researchers believe it may have fallen off its mother's back while she was hunting for snails in the rocks around the cave's entrance, and fallen in.

Fifteen-million years ago, the Riversleigh region was covered with thick rainforest. Massive climate change is suspected to have killed off much flora and fauna during the period.

"This climate change-driven transformation in Australia's wildlife over the last 15 million years is a timely reminder of the probable outcome of the next cycle of climate change, one we appear to have triggered ourselves," Professor Archer said.

The cave at Riversleigh still contains bones from thousands of other animals.

The findings were published in the journal Scientific Reports.