There’s a lot to love about wombats. They’re sturdy creatures, surprisingly fast runners for their size and, believe it or not, they poop in cubes. Literal cubes. But that’s not all that’s interesting about them — they also have a vast history.
In a new study, published Thursday in the journal Scientific Reports, a team of international palaeontologists detail their discovery of a partial animal skull, more than four times the size of any living wombats today.
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The fossil, originally unearthed in 1973 in Lake Pinpa — a remote, dry salt lake in South Australia — has since been attributed to an ancestor of the common wombat from the Oligocene era, though different enough in characteristics that it’s earned its own marsupial family classification.
Mike Archer, a professor for UNSW Science and co-author of the paper, said in a press release that due to the animal’s encasement in clay, they were unsure what it was when they first examined it.
“We found it by probing the dry flat surface of the Lake with a thin metal pole, like acupuncturing the skin of Mother Earth. We only excavated downwards into the clay if the pole contacted something hard below the surface — and in this case it turned out to be the articulated skeleton of a most mysterious new creature.”
Dubbed Mukupirna, which means “big bones” in the Dieri and Malyangapa languages spoken by Indigenous Australians, the skeleton’s remains indicate the animal would’ve been roughly the size of a bear, with teeth that suggest a plant-based diet and powerful limbs for digging. The study’s authors suggest, however, that it may not have been the burrowing type, like contemporary wombats.
According to Robin Beck, co-author on the paper, “Mukupirna clearly was an impressive, powerful beast, at least three times larger than modern wombats.”
“Koalas and wombats are amazing animals,” he said, “but animals like Mukupirna show that their extinct relatives were even more extraordinary and many of them were giants.”
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Scientists have been stunned to find that some ancient crocodiles might have moved around on two feet.
The evidence comes from beautifully preserved fossil tracks in South Korea.
Nearly a hundred of these 18-24cm-long indentations were left in what were likely the muddy sediments that surrounded a lake in the Early Cretaceous, 110-120 million years ago.
The international team behind the discovery says it will probably challenge our perception of crocodiles.
“People tend to think of crocodiles as animals that don’t do very much; that they just laze around all day on the banks of the Nile or next to rivers in Costa Rica. Nobody automatically thinks I wonder what this [creature] would be like if it was bipedal and could run like an ostrich or a T. rex,” Martin Lockley, an emeritus professor at the University of Colorado, US, told BBC News.
The study is sure to provoke a lively debate. Not all researchers will necessarily accept the team’s interpretation.
Prof Lockley and colleagues have assigned the name Batrachopus grandis to the animal that made the tracks, although no physical remains of it have yet been uncovered.
The acknowledgement of the creature’s existence rests solely on the fossil prints themselves. These look very similar in shape, albeit much larger, to those made by Batrachopus crocs that lived tens of millions of years earlier in the Jurassic. Except those older beasts very evidently were quadrupeds – they did walk on all fours.
A bipedal interpretation for the new Korean trace fossils is the only explanation, claims Prof Lockley.
“We can see all the digits, all the ridges in the skin – just as if you were looking at your hands,” he explained. “They put one foot in front of another; they could pass a sobriety test walking on a straight line. And there are no front footprints.”
The depth of the impressions made by the heel also supports the idea of a more upright posture, said team-leader Prof Kyung Soo Kim from South Korea’s Chinju National University of Education.
“Our trackways are very narrow-looking – more like a crocodile balancing on a tight-rope,” he remarked.
“When combined with the lack of any tail-drag marks, it became clear that these creatures were moving bipedally.
“They were moving in the same way as many dinosaurs, but the footprints were not made by dinosaurs. Dinosaurs and their bird descendants walk on their toes.
“Crocodiles walk on the flat of their feet leaving clear heel impressions, like humans do.”
For Prof Lockley, the new prints also help re-interpret a South Korean trackway he and other colleagues described eight years ago. In 2012, this group thought a set of less-well defined and slightly younger indentations might have been left by giant versions of the flying reptiles known as pterosaurs.
These animals are broadly recognised to have shuffled forwards when on the ground using their feet and hands – rather like a bat. This enigmatic trackway, however, had looked bipedal – perhaps the consequence of a pterosaur wading through water with just its feet in contact with the sediment.
Prof Lockley now believes this trackway was also very probably a bipedal Batrachopus.
Prof Phil Manning from the University of Manchester, UK, was not part of the discovery team. As a fossil trackway specialist himself, he described the prints as “very interesting” and welcomed their publication to begin a discussion – but he doubted the interpretation.
“For me, the tracks just don’t fit the overall geometry a crocodilian and what it’s capable of producing,” he told BBC News.
“Look at any videos of living crocs and the rotation of their feet when they’re galloping: it’s outwards, not inwards towards the midline of the trackway. Just from their orientation, it looks more like some kind of dinosaurian track-maker to me. But whether it’s a croc – unfortunately, we just don’t have the fossil bones to tell us.”