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Ancient marsupial tougher than Tassie tiger

Punching above its weight Australia was once home to a carnivore that was powerful enough to bring down prey larger than itself, a new study has found.

The finding, published in the journal PLOS ONE, compared the meat-eating Miocene era marsupial Nimbacinus dicksoni to its closest relative, the recently extinct Tasmanian tiger (Thylacinus cynocephalus) and its cousins, the Tasmanian devil, the spotted-tailed quoll and the Northern quoll.

"We wanted to know if it hunted small or large prey, relative to its size, and if it had similar feeding ecology to its more recently extinct relative, the Tasmanian tiger," says the study's lead author, Dr Marie Attard of the University of New England.

N. dicksoni was part of a now extinct family of Australian and New Guinean marsupial carnivores known as Thylacinidaes.

Most information about species in this family comes from a few scattered fragments of skull.

The recent discovery of a particularly well-preserved N. dicksoni skull from Miocene deposits at Riversleigh in north-western Queensland, provided Attard and colleagues with an opportunity for biomechanical and ecological species studies.

The authors digitally scanned the skull, which included the cranium and part of the mandible, and reconstructed it as a 3D model, which could be compared to similar models of the Tasmanian tiger, and the three living marsupial carnivores.

"This allowed us to do different simulations in the computer, such as shaking, twisting the head, pulling back, and chomping down, all of which reflect different eating behaviours in life," says Attard.

"We could see how well each would bite down and with how much muscle force, and also what sort of stresses each could withstand."

'Opportunistic marsupial'

The authors found the mechanical performance of the skull of N. dicksoni was most similar to that of the spotted-tailed quoll.

"We found that N. dicksoni had quite a powerful bite for its size, showing lower levels of stress in its skull, compared to the thylacine," says Attard.

By comparison, its close relation, the Tasmanian tiger, was showing very high levels of stress along the snout compared to all the other species tested.

"Although only about five kilograms in size, N. dicksoni was a highly opportunistic carnivore, which was able to eat anything from a small marsupial, bird, frog, lizard or snake, to something as big as a bandicoot," says Attard.

The findings provide further support for Attard's earlier study, which showed the Tasmanian tiger could only hunt small prey relative to its size.

"And since it wasn't able to eat a wide variety of species, it was quite vulnerable to extinction. It was much more specialised and limited in the range of prey it could capture," says Attard.