Scientists have confirmed the discovery of a rare fossil belonging to a 25-million-year-old eagle known to prey on koalas.
The Archaehierax sylvestris was one of the first eagles, according to a study published on Monday in the peer-reviewed journal Historical Biology. It dates back to the Oligocene period, 33.9 million to 23 million years ago.
The fossil was found in March 2016 during a research trip by paleontologists from Adelaide's Flinders University to Lake Pinpa in South Australia.
"Lake Pinpa, as a whole, is the most rich fossil site for this time period in South Australia," Trevor Worthy, a vertebrate paleontologist and associate professor at Flinders University, told Live Science.
The earliest known ancestors of modern marsupials, such as bandicoots, possums, kangaroos and wombats, have all been found at the site, along with many plant eating birds such as ducks and cormorants.
But even in this treasure trove of ancient Australian fossils, hawk and eagle specimens have been few and far between, Mr Worthy said.
The newly discovered species is a smaller version of Australia's largest bird of prey, the study showed. It was slender than the wedge-tailed eagle, according to the Western Australia Museum.
The Archaehierax eagle would have had the ability to grasp large prey, given it was nearly 15 centimetres long.
The koalas the eagle was said to have hunted are also extinct, but would probably have been the same size as the koalas today.