Paleontologists Find 25-Million-Year-Old Eagle-Like Bird Fossil in Australia

Wednesday, September 29, 2021

Life reconstruction of Archaehierax sylvestris. Image credit: Jacob Blokland / Taylor & Francis Online.

A new genus and species of extinct predatory bird has been identified from a fossilized partial skeleton unearthed in South Australia.

The newly-identified bird species lived during the Late Oligocene Epoch approximately 25 million years ago.

Dubbed Archaehierax sylvestris, it belongs to the family Accipitridae (eagles, hawks, and Old World vultures).

The ancient bird was larger than the living black-breasted buzzard (Hamirostra melanosternon), but smaller and more gracile than the living wedge-tailed eagle (Aquila audax).

Archaehierax sylvestris was slightly smaller and leaner than the wedge-tailed eagle, but it’s the largest eagle known from this time period in Australia,” said Ellen Mather, a Ph.D. candidate at Flinders University.

“The foot span was nearly 15 cm (6 inches) long, which would have allowed it to grasp large prey.”

“The largest marsupial predators at the time were about the size of a small dog or large cat, so Archaehierax sylvestris was certainly ruling the roost.”

The partial skeleton of Archaehierax sylvestris, which is comprised of 63 bones, was recovered from the Late Oligocene sediments of the Namba Formation at Lake Pinpa in South Australia.

“With eagles at the top of the food chain, they are always few in number — and so are infrequently preserved as fossils,” added Dr. Trevor Worthy, a paleontologist at Flinders University.

“It’s rare to find even one bone from a fossil eagle. To have most of the skeleton is pretty exciting, especially considering how old it is.”

Archaehierax sylvestris had short wings, and was adapted for flight within enclosed forests.

“The fossil bones reveal that the wings of Archaehierax sylvestris were short for its size, much like species of forest-dwelling eagles today,” Mather said.

“Its legs, in contrast, were relatively long and would have given it considerable reach.”

“The combination of these traits suggest Archaehierax sylvestris was an agile but not particularly fast flier and was most likely an ambush hunter.”

“It was one of the top terrestrial predators of the Late Oligocene, swooping upon birds and mammals that lived at the time.”

The discovery of Archaehierax sylvestris is described in a paper in the journal Historical Biology.


Ellen K. Mather et al. An exceptional partial skeleton of a new basal raptor (Aves: Accipitridae) from the late Oligocene Namba formation, South Australia. Historical Biology, published online September 27, 2021; doi: 10.1080/08912963.2021.1966777