An early relative of the wombat with a powerful bite and a possum with large teeth have been discovered in central Australia, helping to solve an evolutionary puzzle.

The fossils, deposited about 25 million years ago in the late Oligocene, were found by Flinders University paleontologists in 2014, 2020 and 2022 near the small Arrernte township of Pwerte Marnte Marnte in the southern Northern Territory.

They give key insights into the diet and lifestyle of long-extinct marsupials that lived in a once-lush forest landscape dominated by megafauna, including giant flightless birds and crocodiles.

“These curious beasts are members of marsupial lineages that went extinct long ago, leaving no modern descendants,” PhD candidate Arthur Crichton said.

“Learning about these animals helps put the wombat and possum groups that survive today in a broader evolutionary context.”

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The newly described possum species, called Chunia pledgei, had teeth with lots of bladed cusps that were positioned side by side.

“We know that these animals had a lemur-like short face, with particularly large forward-facing eyes, but until more complete skeletal material is known their ecology will likely remain mysterious,” Mr Crichton said.

The new species is named after South Australian paleontologist Neville Pledge, who discovered fossils in rocks east of Lake Eyre.

The other new species, called Mukupirna fortidentata, was a larger distant relative of wombats and had jaws and teeth shaped to suggest a powerful bite with large and steeply upturned incisors.

Weighing about 50 kilograms, it was among the largest marsupials of its time.

This species is thought to be part of an extinct evolutionary lineage, Mukupirnidae, that diverged from a common ancestor with wombats more than 25 million years ago.

“While wombats were very successful over the succeeding period, the mukupirnids seem to have gone extinct sometime before the end of the late Oligocene,” paleontologist Gavin Prideaux said.

“This is an interval in Australia’s climate that saw a steady increase in aridity and seasonally restricted rainfall, reshaping the environment.”

Evidence of the ancient wombat was compiled from 35 specimens from different individuals, including a partial skull and several lower jaws.

-AAP