Artist reconstruction of a malleodectid from 15 million years ago chomping down on what appears to have been its favorite food — snails. (Peter Schouten)

Australia's Riversleigh World Heritage site — a limestone cave filled with countless skeletons, remains of poor creatures that plummeted in over the course of millions of years — is a who's who of weird extinct animals.

From its depths, scientists have uncovered fossils of the Thingodonta, a woodpecker-like marsupial that used its teeth to gnaw bugs out of tree bark. They've found evidence of an extinct tusked kangaroo relative, whose scientific name is (I kid you not) Balbaroo fangaroo. They've excavated the remains of drop crocs, ancient crocodiles that attacked their prey by dropping out of trees. And they discovered the gigantic Dromornis, affectionately known as the "Demon Duck of Doom," which at 10 feet tall was among the biggest birds in the world.

Now, scientists say they have a small but appropriately strange new creature to add to the collection: The malleodectes mirabilis, or "wondrous hammer biter" — a ferret-sized relative of modern Tasmanian devils that subsisted on a diet of escargot.

"Malleodectes mirabilis was a bizarre mammal, as strange in its own way as a koala or kangaroo," University of New South Wales paleontologist Mike Archer, the lead author of a study on the fossil published in Scientific Reports, said in a statement.

These creatures were equipped with huge, hammer-like premolars that allowed them to eat snails whole — shell and all – the likes of which researchers have never seen in a mammal before.

In the four decades that Australian scientists have been excavating at Riversleigh, they've uncovered isolated bits and pieces of these strange snail eaters. But it didn't become clear that they were looking at an entirely distinct family of animals until they discovered the skull of a 15-million-year-old malleodectid baby encased in the cave's limestone floor.

"The juvenile malleodectid could have been clinging to the back of its mother while she was hunting for snails in the rocks around the cave's entrance, and may have fallen in and then been unable to climb back out," University of New South Wales paleontologist Suzanne Hand said in the statement.

From its jaw, Archer could tell that the animal was on the cusp of adulthood: just beneath its baby teeth, a row of adult teeth was waiting, about to emerge.

Teeth are some of paleontologists' best tools for identifying fossils, since they say so much about who a creature was: how large it grew, how old it was and, most importantly, what it liked to eat. So all those pearly whites gave Archer and his team a pretty good sense of how the creature fit into the larger marsupial family tree.

They decided that the malleodectids were their own family (in the taxonomical sense of the term), cousins of established groups like the dasyuridae (which include Tasmanian devils) and the myrmecobiidae (which comprises a single species, the numbat).

But the malleodectids have no hope of a family reunion. They went extinct not long after the juvenile from Archer's study died, thanks to a period of intense climate change that transformed Australia's rain forests into dry grasslands. If the baby malleodectid has any siblings, they're probably buried in the ground as well.

At a spot he calls "New Riversleigh," Archer thinks he might have found one. Whether or not that creature turns out to be a relative is a story for another study.

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