Why megafauna southwest of Mackay went extinct
Dating back 40,000 years, they include a giant wombat, croc and a marsupial lion related to the koala
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PALAEONTOLOGISTS have explained why megafauna including giant wombats and marsupial lions found at a dig site southwest of Mackay went extinct.
Queensland Museum palaeontologist Dr Scott Hocknull and a team of scientists have spent more than a decade uncovering 16 megafauna species dating back 40,000 years at South Walker Creek, 40km west of Nebo.
The unearthed species now extinct included the half-tonne Diprotodon related to wombats, giant reptiles like a 7m long freshwater crocodile and the Thylacoleo or Marsupial Lion – a relative of koalas and possums, Dr Hocknull said.
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“(The Thylacoleo) is the size of a lion with meat-cleaving teeth and bone-crunching molars,” he said.
“It could essentially give you a bear hug and was potentially tree-dwelling as well – the first Australian instance of the drop bear.
“At 170kg in weight, it’s a huge animal and a nasty piece of work.”
Dr Hocknull said the “weird” species evolving over millions of years of isolation were discovered by chance during the Barada Barna people’s cultural heritage clearance at a BHP-operated site in 2008.
“It was a mind blow,” he said.
“I had just assumed, based on what we knew about the tropics, that there would be a handful of bones … (but) we saw literally hundreds of bones in the ground sticking out, some really well preserved.”
Teaming with other scientists, they were able to date the fossils and work out what type of environment the megafauna lived in.
Dr Hocknull said the site, now a dried-up creek, was once teeming with lush grasses and rivers.
And a reason so many fossils were found, usually “scarce as hen’s teeth” in the tropics, was because the “massive” crocodiles dragged their prey into the river and billabongs, he said.
But they had not found human remains, Dr Hocknull said, suggesting over-hunting could not explain the megafaunas’ extinction.
“If we had people arriving 65,000 years ago and our megafauna on the eastern coast of Australia are still quite happy 40,000 years ago … then clearly, they didn’t just disappear rapidly.
“Instead, we (found) their extinction (was) coincident with major climatic and environmental deterioration both locally and regionally, including increased fire, reduction in grasslands and loss of freshwater.
“Together, these sustained changes were simply too much for the largest of Australia’s animals to cope with.”
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Project Dig is an ongoing partnership between BHP Mitsui Coal and the Queensland Museum.
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