‘Gentle giant’: Scientists announce new species of ancient Aussie marsupial

Scientists have revealed details of a wombat-like marsupial as big as a bear that roamed prehistoric Australia 25 million years ago. 

The ancient marsupial, named Mukupirna nambensis, is one of the oldest Australian marsupials discovered so far and one of the best preserved to date. 

The creature’s body mass is estimated to have been between 143 to 171 kilograms, roughly five times larger than living wombats, and more similar in size to a panda. 

But despite its impressive size, the creature has was a ‘gentle giant’ that probably stuck to eating plants.  

Researchers describe the remains of the prehistoric mammal’s skull and partial skeleton from the Lake Eyre Basin of South Australia.

The fossils date back to the late Oligocene period, somewhere between 25 million and 26 million years ago, when continents were closer together than they are today. 

‘Mukupirna clearly was an impressive, powerful beast, at least three times larger than modern wombats,’ said study lead Dr Robin Beck from the University of Salford. 

‘It probably lived in an open forest environment without grasses, and developed teeth that would have allowed it to feed on sedges, roots, and tubers that it could have dug up with its powerful front legs.’

The palaeontologists made the discovery back in 1973 in the clay floor of Lake Pinpa, a remote, dry salt lake east of the Flinders Ranges in South Australia.

The discovery of Mukupirna was partly due to good luck after an unusual change in local conditions exposed the fossil on the floor of the dry salt lake.

‘It was an extremely serendipitous discovery because in most years the surface of this dry lake is covered by sands blown or washed in from the surrounding hills,’ said study co-author Professor Mike Archer at the University of New South Wales. 

‘But because of rare environmental conditions prior to our arrival that year, the fossil-rich clay deposits were fully exposed to view – and this unexpected view was breathtaking.’

The team conducted analysis based on 79 cranium and teeth samples and 20 postcranial samples – bits of skeleton that aren’t from the skull. 

Mukupirna’s teeth, which were housed within its 7.8-inch skull, indicate that it subsisted only on plants, while its powerful limbs suggest it was probably a strong digger. 

Anatomical features identified in the skeleton are indicative of digging behaviour, such as adaptations to the forearms commonly seen in burrowing animals of today. 

However, evidence from previous fossils dated to a later time suggest the new species was less well-adapted to burrowing than its later relatives. 

Mukupirna nambensis may not have been capable of the true burrowing behaviour seen in modern wombats, but may have used scratch-digging to access food items below the surface, such as roots and tubers.   

One particular characteristic that’s present in modern wombat species – specialised molars capable of continuous growth – was notably absent in Mukupirna.  

Due to its distinctiveness, researchers christened it as a new family altogether, called Mukupirnidae, of which it is the only genus and species. 

Mukupirna nambensis comes from the words muku (‘bones’) and pirna (‘big’) of the Aboriginal languages spoken in the surrounding areas. 

Mukupirna is however, part of the vombatiform taxonomic group, which also includes wombats, koalas and their fossil relatives. 

It’s also not the largest of this group – the largest known vombatifom marsupial was the relatively recent Diprotodon, which weighed over 2 tonnes (2,000kg) and survived until at least 50,000 years ago.

‘Koalas and wombats are amazing animals, but animals like Mukupirna show that their extinct relatives were even more extraordinary, and many of them were giants,’ said Dr Beck.  

‘The description of this new family adds a huge new piece to the puzzle about the diversity of ancient, and often seriously strange marsupials that preceded those that rule the continent today,’ added co-author Julien Louys, an associate professor at Griffith University. 

Also found around the fossil deposits at the time of the discovery were the remains of stiff-tailed ducks and flamingos.

‘On the surface, and just below we found skulls, teeth, bones and in some cases, articulated skeletons of many new and exotic kinds of mammals,’ said Professor Archer.

‘As well, there were the teeth of extinct lungfish, skeletons of bony fish and the bones of many kinds of water birds including flamingos and ducks.

‘These animals ranged from tiny carnivorous marsupials about the size of a mouse right up to Mukupirna which was similar in size to a living black bear. 

‘It was an amazingly rich fossil deposit full of extinct animals that we’d never seen before.’

The species and genus is described further in the journal Scientific Reports.