Paleontologists have uncovered the fossilized remains of a new species of the Pleistocene eagle genus Dynatoaetus in Victoria Fossil Cave at Naracoorte, Australia.
A reconstruction of a flock of Cryptogyps lacertosus (left side) and several individuals of Dynatoaetus pachyosteus (right side) feeding on a carcass of Diprotodon optatum in the Late Pleistocene Naracoorte landscape. Image credit: John Barrie.
The newly-described species lived during the Pleistocene period more than 50,000 years ago.
The bird was similar size to the living wedge-tailed eagle (Aquila audax) and the extinct Australian vulture (Cryptogyps lacertosus).
Named Dynatoaetus pachyosteus, it had short, stout wing bones and very large and robust leg bones.
“This new eagle species would have been similar in wingspan to a wedge-tailed eagle, now Australia’s largest living eagle of prey, but its bones seem much more robust — especially its leg bones, suggesting it was even more powerful and heavily built,” said Flinders University paleontologist Ellen Mather.
“The Dynatoaetus genus was endemic to Australia, meaning it was found nowhere else in the world.”
“Now we have found two species and know this genus is not particularly closely related to any eagles outside Australia, we suggest that this group of raptors must have been in Australia for quite some time, rather than being a relatively recent arrival.”
“However, our analyses suggest they may be related to the large crested serpent eagle (Spilornis cheela) and the Philippine eagle (Pithecophaga jefferyi), top predators in the tropical jungles Southeast Asia and New Guinea.”
Cryptogyps lacertosus was the size of a modern-day wedge-tailed eagle. Its bones — including an almost complete pair of wings from a single individual — were recovered from an underwater cave, known as the Green Waterhole or Fossil Cave, near Mount Gambier.
In the new study, Dr. Mather and colleagues connect these specimens to the bones they studied from a Nullarbor cave in Western Australia — suggesting Cryptogyps lacertosus was more a primitive vulture than previously thought.
“Most vultures in the Aegypiinae subfamily (Old World vultures related to the griffon vulture) have extremely light wing bones filled with air cavities, thought to help with long periods of soaring flight,” Dr. Mather said.
“But Cryptogyps lacertosus seems to have lacked this adaptation. This could indicate that this bird was not as efficient a soarer compared to its living relatives.”
Both species of Dynatoaetus — Dynatoaetus pachyosteus and the recently-described Dynatoaetus gaffae — were found in Victoria Fossil Cave deposits and so lived in the area between 500,000 and 200,000 years ago.
Eagle fossils are rare, so precisely when these birds went extinct is unknown.
However, the researchers were able to place a date on Cryptogyps lacertosus from Green Waterhole Cave.
They suggest that this bird was alive around 60,000 years ago. This means it had survived right up to Australia’s megafaunal mass extinction.
“It is quite likely that the extinction of the large marsupials played a key role in the demise of Cryptogyps lacertosus, and possibly the giant eagles as well,” Dr. Mather said.
“Whatever caused the extinction of at least the vulture and two other eagles, the result is that Australia has only one largish raptor in its inland fauna today.”
“This is unusual in the world, as most continents have several eagles and vultures.”
“We now know that the extinction not only removed large groups from the mammal fauna but that the absence of vultures is a recent loss and that Australia had two other eagles — both able to take rather larger prey than the wedge-tailed eagle.”
The study was published in the Alcheringa, an Australasian Journal of Palaeontology.
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Ellen K. Mather et al. 2023. Pleistocene raptors from cave deposits of South Australia, with a description of a new species of Dynatoaetus (Accipitridae: Aves): morphology, systematics and palaeoecological implications. Alcheringa, in press; doi: 10.1080/03115518.2023.2268780