Super-Sized Australian Animals Driven To Extinction 40,000 Years Ago By Climate Change, Not Humans

South Walker Creek was once the stomping ground of over 16 different super-sized megafauna. R. Bargiel, V. Konstantinov, A. Atuchin & S. Hocknull (2020), Queensland Museum.

Katy Pallister 20 May 2020, 11:58

South Walker Creek, located in northern Australia, was once home to a diverse group of colossal megafauna, new research has revealed. Seven-meter-long freshwater crocodiles, giant bucktoothed wombats, and the largest kangaroos to ever exist on Earth roamed the ancient flood plains between 60,000 to 40,000 years ago.

Some of these animals were previously thought to have been driven to extinction by the over-hunting of recently arrived humans, but the team’s decade-long excavation efforts support a different ending for at least 13 of the giant beasts; one of drought, fire, and vegetation loss.

“The megafauna at South Walker Creek were uniquely tropical, dominated by huge reptilian carnivores and mega-herbivores that went extinct around 40,000 years ago, well after humans arrived onto mainland Australia,” Dr Scott Hocknull, a Queensland museum palaeontologist who led this mammoth project, said in a statement. “We cannot place humans at this 40,000-year-old crime scene, we have no firm evidence… Instead, we do find that their extinction is coincident with major climatic and environmental deterioration…These sustained changes were simply too much for the largest of Australia’s animals to cope with.”

Yep, these were some pretty big beasties.

As documented in the team’s study, published in Nature Communications, the fossils of the Creek’s megafauna show that when thriving they were pretty badass creatures. At the top of the predatory chain were mostly giant reptiles, including the 7-meter-long (23-foot) freshwater crocodile and two other giant lizards – a 6-meter-long (20-foot) goanna, and another similar in size to the Komodo Dragon.

Their prey were megamammals. Giant wombats with continuously growing teeth, a strange “bear-sloth” marsupial, and the largest kangaroo ever discovered. Predicted to weigh 274 kilograms and have a height of 2.5 meters (8 feet), these yet-to-be-named kangaroos appear to only be found at South Walker Creek.

The jaw bone from the extinct giant marsupial Diprotodon, excavated at South Walker Creek. Queensland Museum

Trumping this kangaroo in the size category, however, was the 3-ton giant marsupial Diprotodon. But these plant-eating mammals had to beware of another predator amongst them – the deadly Thylacoleo. Boasting teeth that can cut flesh and crack bones, this marsupial “lion” would certainly not have been an animal you’d wish to cross paths with.

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The marsupial lion Thylacoleo. V. Konstantinov, A. Atuchin, R. Allen, S. Hocknull/ Queensland Museum.

South Walker Creek was first brought to the attention of researchers in 2008, when the Barada Barna people discovered a fossil during a cultural heritage clearance. In the excavations that have followed, researchers have unearthed a magnificent array of findings. From never-before-seen megafauna fossils, to fossilized seeds, leaves and insects, palaeontologists have been able to build up a picture of the site’s past landscape and inhabitants.

Yet, for three of the 16 giant species discovered at the Creek, researchers didn’t have to imagine them, as the emu, the red kangaroo, and the saltwater crocodile still exist today. But Hocknull says that the extinction of their past acquaintances should serve as a warning to help us prevent them from facing a similar fate.

“This research has significant bearing on how we see our current landscape and the impacts of climate change, fire, vegetation change and availability of water on the survival of our existing modern megafauna – both native and domestic,” Hocknell said.

“Not since the time of the dinosaurs has Australia been home to such magnificent giants, and yet within a geological instant, they were gone forever. There is a message in that for everyone.”

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