Ancient “toothy” wombat cousin found near Alice Springs sheds light on how today’s marsupials evolved

Remains of a previously unknown ancient wombat, which lived 25 million years ago, have been discovered in central Australia.

Called Mukupirna fortidentata, the animal is thought to share a common ancestor with modern wombats, but has been described as a cross between a wombat and the extinct Thylacoleo, also known as the “marsupial lion”.

Flinders University palaeontologists uncovered 35 different Mukupirna specimens after digging the hard limestone of Pwerte Marnte Marnte in the Northern Territory for over 2,000 hours. The fossil site is in the central Australian desert about 75 kilometres south of Alice Springs.

Twenty-five million years ago, during the late Oligocene, Australia’s centre would have looked very different. For one, it was much wetter and covered in forest. In fact, there were vast freshwater lakes which were home to flamingos and freshwater dolphins.

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Another species of Mukupirna discovered in 2020, Mukupirna nambensis, was found dating back to around the same time at Lake Pinpa in what is now northeastern South Australia. It was probably twice the size of its close relative Mukupirna fortidentata.

“They are a bit of an evolutionary intermediate between wombats and their more koala-like relatives,” says Flinders PhD candidate Arthur Crichton in a BBC article.

“It’s not really correct to say that Mukupirna is an ancestral wombat either. It seems to have gone off on its own evolutionary tangent that is very much unique in the context of marsupial evolution,” Crichton says in an ABC article.

By measuring its teeth and limb bones, the scientists were able to work out that M. fortidentata would have weighed up to 50 kilograms. This would still have made it one of the largest marsupials alive at the time.

It had molars similar to those of some monkeys, like macaques. But its front teeth are huge and spike-shaped, like a rodent. It would have had a powerful bite, says Crichton.

But Crichton says that the animals teeth “pretty much confirm it’s not a carnivore,” adding that its striking dentition was “really quite specialised for processing hard foods like tough fruits, nuts and tubers.”

The team also found the remains of Chunia pledgei, likely an ancient relative of possums.

There is precious little in the fossil record about Australia’s animals between 55 and 25 million years ago. This means every new find from earlier in Australia’s prehistory will help us better understand how modern Australian fauna evolved.

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“These are some of the oldest marsupials known from Australia and are really important for understanding how our iconic marsupials came to be,” Crichton says.

Crichton is first author on a paper about the find published in Alcheringa: An Australasian Journal of Palaeontology and also appearing in the Journal of Vertebrate Paleontology.