Researchers at Flinders University may have discovered what ultimately led to the extinction of Australia’s last massive thunderbird, the genyornis newtoni.
The clue came with the discovery of a rare fossil. The discovery, by researchers at Flinders University, revealed serious bone infections in several dromornithid remains mired in the 160 km² of the Lake Callabonna fossil reserve, 600 km northeast of Adelaide.
At 230kg, the genyornis weighed about five or six times more than an emu and stood about two meters tall, but getting stuck in the dangerous mud of the lake wasn’t the giant birds’ only concern.
Some also appear to have had a painful illness, which lead researcher Phoebe McInerney says has hampered their mobility and foraging.
“The fossils showing signs of infection are associated with the chest, legs and feet of four individuals,” said the doctoral student.
“They were said to have been increasingly weakened, suffering from pain, making it difficult to access water and food.
“It is a rare thing in the fossil record to find one, let alone several well-preserved fossils with signs of infection. We now have a much better idea of the challenges in the life of these birds. “
The study found that about 11% of the birds suffered from osteomyelitis.
“We see foamy, woven bones, large abnormal growths and cavities in their fossil remains,” McInerney said.
The discovery of several individuals in the population with osteomyelitis suggests that a somewhat complex situation could have caused the phenomenon.
Study co-author, Associate Professor Lee Arnold, dated the salt lake sediments in which genyornis was found, linking them to a period of severe drought beginning around 48,000 years ago.
Back then, thunderbirds and other megafauna, including former parents of wombats and kangaroos, faced major environmental challenges.
As the continent dried up, large inland lakes and forests began to disappear and central Australia became a flat desert.
With the worsening conditions, associate professor Trevor Worthy believes food resources would have been reduced, causing considerable stress to the animals.
“From studies of live birds, we know that harsh environmental conditions can have negative physiological effects,” he said.
“We therefore infer that the Lake Callabonna genyornis population should have struggled with such conditions.”
It now appears that the effects of periods of severe drought included high rates of bone infection, with weakened individuals more likely to get stuck in deep mud and die.
In the absence of conclusive evidence to suggest that genyornis newtoni survived well beyond this period, it was likely a prolonged drought and high rates of disease contributed to its eventual extinction.
The research results have been published in Papers in Palaeontology.