Australia's skies ruled by eagle-like raptor 25 million years ago

Sept. 27 (UPI) -- Paleontologists in Australia have recovered one of the oldest and best-preserved raptors in the world.

Researchers found the remains of the ancient bird of prey on a remote cattle ranch in the Outback.

The 25-million-year-old raptor bones -- detailed Monday in the journal Historical Biology -- belonged to Archaehierax sylvestris, an eagle-like species that ruled Australia's skies during the late Oligocene.

"This species was slightly smaller and leaner than the wedge-tailed eagle, but it's the largest eagle known from this time period in Australia," first study author Ellen Mather said in a press release.

"The foot span was nearly 15 centimeters 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 was certainly ruling the roost," said Mather, a doctoral candidate at Flinders University.

Because ancient raptors were at the top of the food chain, their population numbers remained relatively modest, making raptor fossils rare -- and well-preserved raptor fossils even rarer.

"It's rare to find even one bone from a fossil eagle," said co-author Trevor Worthy, an associate professor at Flinders. "To have most of the skeleton is pretty exciting, especially considering how old it is."

The raptor's remains were recovered from the banks of an ancient lake. Today, Australia's outback is a dry and desolate place, but the continent's interior was once much wetter and covered with dense forest.

Many birds of prey prefer to hunt grasslands and freshwater habitat, where they can soar and dive unencumbered. Navigating tree limbs while swooping down on prey requires special evolutionary adaptations.

Though Archaehierax was the largest flying predator of its time, its wings were relatively short, allowing the bird to make sharp turns and navigate tight quarters. Today, most forest-dwelling raptors also sport short wings.

While Archaehierax had shorter wings, it's stature, however, wasn't all that short. The bird's long legs and big talons extended its reach, allowing it to more easily snatch small mammals from tree limbs and the forest floor.

"The combination of these traits suggest Archaehierax was an agile but not particularly fast flier and was most likely an ambush hunter," Mather said. "It was one of the top terrestrial predators of the late Oligocene, swooping upon birds and mammals that lived at the time."

The neatly preserved remains of Archaehierax not only allowed researchers to better understand how the eagle-like raptor lived and hunted, but also helped scientists properly position the species on its family tree.

"We found that Archaehierax didn't belong to any of the living genera or families. It seems to have been its own unique branch of the eagle family," Mather said. "It's unlikely to be a direct ancestor to any species alive today."