How Australia’s ancient giant animals went extinct

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Australia Once home to many gigantic animals – megafauna – whose existence likely coincided with the arrival of humans.

New research from Flinders University has now revealed how these animals could have gone extinct.

A rare fossil find in South Australia in particular has drawn attention to the plight of dromornithids, the “thunderbirds” (Genyornis newtoni).

Australia’s ancient “thunderbirds” became extinct tens of thousands of years ago. (Flinders University)

Research published in the journal Papers in Palaeontology revealed that several Genyornis fossils had severe bone infections.

Lead author Phoebe McInerney said the condition would have hampered the birds’ mobility and foraging.

“The fossils showing signs of infection are associated with the chest, legs and feet of four individuals,” she said.

“They were said to have been increasingly weakened, suffering from pain, making it difficult to find food and water.”

Megafauna
A new study has shown that a number of people suffer from severe bone disease. (Flinders University)

The remains were found in the salt beds of Lake Callabonna, about 600 km northeast of Adelaide.

The giant Genyornis weighed about 230 kg – five to six times that of an emu – and was about two meters tall.

The study found that about 11% of the birds suffered from osteomyelitis, a serious infection of the bones.

University of Adelaide co-author Associate Professor Lee Arnold dated the lake sediments in which Genyornis Was found. This linked the deaths of these individuals to a period of severe drought that began around 48,000 years ago.

During this drought, these giant birds, along with other megafauna species, including the ancient giant relatives of wombats and kangaroos, faced major environmental challenges.

Megafauna
Other megafauna have probably disappeared due to changes in the terrain. (Flinders University)

As the landscape dried up across Australia, the great inland lakes and forests began to disappear and central Australia became flat desert plains now covered with salt lakes.

“As the drought conditions worsened, food resources would have been reduced, which would have caused considerable stress to the animals,” says co-author, Associate Professor Trevor Worthy, of the Paleontology Laboratory at Flinders University. .

“From studies on live birds, we know that harsh environmental conditions can have negative physiological effects, so we infer that the Lake Callabonna population of Genyornis would have had a hard time going through such conditions. “

Without any conclusive evidence to suggest that Genyornis newtoni survived well beyond this time, it is likely that prolonged drought and high disease rates contributed to the eventual extinction of this species.

At another fossil site, the Naracoorte Caves in South Australia, modeling suggested that changes in Australian plant life, brought on by human land use and climate change, may have contributed to the extinction of ancient plant eaters such as Diprodoton.

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The study was published in the journal Ecoography.

“By modeling the ecological community using powerful computational methods, we can simulate the relative position of any extinct or modern species in the global food chain as it existed several millennia ago, and then estimate at what point these species were vulnerable to changes in the ecosystem, ”says Flinders University evolutionary ecologist and lead author Dr. John Llewelyn.

“Our models revealed that extinct species of megafauna, particularly large plant-eaters, were more vulnerable to these ‘upward’ cascades of co-extinction triggered by changes in plant species than species we still have today. . “

The analyzes also showed that species at the bottom of the food chain, such as herbivores which only specialized in a few plant species for food, were particularly vulnerable.


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