Eagle Like Raptor That Hunted Ancient Koala Bear Sized Prey 25 Million Years Ago Unearthed In Australia

Scientists have unearthed the remains of a 25-million-year old eagle like-raptor that soared above the Australian outback preying on animals the size of koala bears and flamingos with its enormous talons.

Researchers from Flinders University unearthed the Achaehierax sylvestris (‘ancient hawk of the forest’) at Lake Pinpa, 400 kilometres (248 miles) north of Adelaide in 2016 and the results of its analysis were released yesterday (27th September).

Archaeologists excavated 63 of the eagle-like raptor’s bones making it one of the most complete raptor fossils ever discovered from the late Oligocene period.

An illustration of the eagle that ruled the food chain of South Australia 25 million years ago. (Jacob Blokland/Newsflash )

The researchers suspect that it may be an entirely new species although they refrained from confirming this as more research will be needed.

Ellen Mather, a Flinders University PhD candidate and the first author of the paper, said: “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.

“The foot span was nearly 15 centimetres (5.9 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 was certainly ruling the roost.”

Skeleton of an osprey by Eyton (1867) with shaded sections indicating which bones are preserved in the fossil of Archaehierax sylvestris. (Historical Biology/Newsflash)

Study co-author and Associate Professor Trevor Worthy said: “With eagles at the top of the food chain, they are always few in number – and so are infrequently preserved as fossils.”

He added: “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.”

The remains of the 25-million-year old apex predator were found on the shore of a dry lake called Lake Pinpa which is now a desert.

Palaeontologists from Flinders University excavating fossils near Lake Pinpa, South Australia. L to R: Aaron Camens, Amy Tschirn, Jacob Blokland and Kailah Thorn. (Historical Biology/Newsflash)

However, Lake Pinpa was a very different place when the ‘hawk of the forest’ was soaring through the sky picking off small mammals for food.

The desert would have been covered in a thick forest with a huge spectrum of fauna and flora.

Mather said: “The fossil bones reveal that the wings of Archaehierax (pron. ah-kay-hi-rax) were short for its size, much like species of forest-dwelling eagles today. Its legs, in contrast, were relatively long and would have given it considerable reach.”

Left tarsometatarsus (lower leg bone) of the fossil raptor Archaehierax sylvestris, beside Aquila audax (Wedge-tailed Eagle). The fossil was distorted during burial so the top half is rotated 90 degrees to the lower half. (Historical Biology/Newsflash)

He added: “The combination of these traits suggest Archaehierax 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.”

According to the researchers, Archaehierax would have preyed on animals the size of koalas, flamingos and possums amongst other species that inhabited the trees around the lake.

Worthy said: “I have studied this system for many years now, and this is the most exquisite fossil we have found to date,”

Collection of fossilised bones from the 25-million-year-old ancient eagle-like raptor. (Historical Biology/Newsflash)

He added: “The completeness of the Archaehierax skeleton allowed us to determine where it fits on the eagle family tree. It shows a range of features unlike any seen among modern hawks and eagles.

“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.”

The researchers believe that the eagle is unlikely to be a direct ancestor of any species alive today.

Collection of fossilised bones from the 25-million-year-old ancient eagle-like raptor. (Historical Biology/Newsflash)

The study was published under the title ‘An exceptional partial skeleton of a new basal raptor (Aves: Accipitridae) from the late Oligocene Namba formation, South Australia’ in the journal Historical Biology on 27th September.

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