Fossil shows a Wombat relative who weighed over 300 pounds

Wombats and koalas stand out as strange animals even on a continent famous for strange animals. They are also closer relatives to each other.

Koalas eat eucalyptus, resemble live teddy bears, and, like Australia’s other endangered native fauna, need occasional rescues. Wombats poop in cubes, yes, cubes, which they leave out and even stack to mark their territory. As for the animal itself, imagine the incarnate chonk, a ball of fluff and grease dug out by muscular little brawls.

Now multiply that five times. That’s the size of a long-lost new member of the same group of animals, Mukupirna nambensis, a mega-wombat that tipped the scales at over 300 pounds. Scientists believe it escaped into the soil of the Australian rain forest about 25 million years ago.

“I would compare it to a black bear,” said Robin Beck, a paleontologist at the University of Salford in England, who described the fossils of the wow-inducing wombat on Thursday in the journal Scientific Reports.

The strong species is the newest member of a large menagerie. For millions of years to this day, large and unique marsupials flourished in Australia and New Guinea, isolated from the rest of the world.

Koalas and wombats are the only surviving remnants of an extinct group called vombatiforms, “wombat-like” animals that were more diverse than any other type of marsupial.

Beyond the new Mukupirna., Other extinct vombatiforms became even larger, such as Diprotodon, a herbivore that weighed almost as much as a rhino. Or a mysterious horse-sized animal with a trunk. Or the “marsupial lion”, a carnivore comparable to today’s African lions.

“You’d think they could do anything, they could take over the world,” said Vera Weisbecker, an evolutionary biologist at Flinders University in Australia who was not part of the research team. “They didn’t, so that’s frustrating.”

Credit…Julien Louys / Griffith University and Robin Beck / University of Salford

Because so few high-quality fossil sites have been discovered on the continent, scientists have long struggled to learn about these lost animals.

Mukupirna, which means “big bones” in the diyari language spoken near where it was found, languished for decades before being studied. It was excavated in July 1973 by paleontologists working in the dry bed of Lake Pinpa in South Australia.

“We were all desperately eager to find ancient fossils of Australian animals, because they are so rare,” said Michael Archer, then a doctoral student on the expedition now working at the University of New South Wales in Australia.

The original team held a thin metal rod to lead into the clay. Sometimes it happened cleanly. Other times they heard a metallic sound of buried bone. Closer to the surface, they discovered and then published an alien ecosystem: lung teeth, possums, and freshwater dolphins; flamingo bones, kangaroos that galloped instead of jumping and a large koala, among others.

Large fossils like Mukupirna that echoed off the pole were wrapped in plaster and sent to the American Museum of Natural History in New York. He remained there for more than four decades, until Dr. Beck and his colleagues obtained high-resolution images and linked him to Dr. Archer.

From his skull, the team found teeth that looked like those of a baby wombat, allowing them to include Mukupirna. in a family tree of other large wombat relatives. They also discovered that the animal’s arms would have made it an efficient digger, allowing it to search for roots and tubers, although it probably couldn’t dig like modern wombats.

“That would be a great burrow,” said Dr. Archer.

Other teams are now excavating the same Pinpa Lake site, so more fossils can still be discovered. But as for whether Mukupirna shared the cubic poop of modern wombats, science has yet to offer a definitive answer.

“Unfortunately, neither the poop nor the intestines have been preserved,” said Dr. Beck. “I couldn’t rule this out.”