AsianScientist (Jun. 3, 2016) – Fossil remains of a previously unknown family of carnivorous Australian marsupials that lived 15 million years ago have been discovered at the Riversleigh World Heritage Fossil Site in Queensland. The research team, from the University of New South Wales, published details of the ferret-sized marsupials in Scientific Reports.
“Malleodectes mirabilis was a bizarre mammal, as strange in its own way as a koala or kangaroo,” said Professor Mike Archer, the lead author of the study.
“Uniquely among mammals, it appears to have had an insatiable appetite for escargot—snails in the whole shell. 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.”
Isolated teeth and partial dentitions of this unusual group, known as malleodectids, had been unearthed over the years at Riversleigh, where Archer and colleagues have excavated for almost four decades. But the profoundly different nature of the marsupials was not realized until a well-preserved portion of the skull of a juvenile was found in a Middle Miocene cave deposit at Riversleigh.
This juvenile specimen was only recently extracted from its limestone casing, which made it available for study with modern techniques including micro-computed tomography. The young animal still had its baby teeth, and was teething, with adult teeth that had been about to erupt when it was alive still embedded in its jaw.
“Details of the canine, premolar and molar teeth of this specimen have enabled its relationships to other Australian marsupials to be determined with reasonable confidence,” said Archer.
“Although it is very different from the others, it appears to have been related to the dasyures—marsupial carnivores such as Tasmanian devils and the extinct Tasmanian tigers that are unique to Australia and New Guinea.”
Nothing remains of the cave at Riversleigh except its limestone floor, which contains the bones of thousands of animals that fell into, or lived in, the ancient cave.
“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,” said team member, Professor Suzanne Hand.
According to Hand, many other animals that lived in this lush forest met a similar fate, with their skeletons accumulating one on top of another for perhaps thousands of years, until the cave became filled with paleontological treasures.
Over millions of years, the walls and ceiling of the cave were eroded away, leaving only the fossil-rich floor, which was discovered by Riversleigh Project team members in 1990.
The article can be found at: Archer et al. (2016) A New Family of Bizarre Durophagous Carnivorous Marsupials from Miocene Deposits in the Riversleigh World Heritage Area, Northwestern Queensland.
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Source: University of New South Wales; Photo: Peter Schouten.
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