Ancient crocs walked on two legs the size of ours

A reconstruction of the ancient landscape of South Korea with crocodile track-makers. (Credit: Anthony Romilio)

Some species of ancient crocodiles walked on their two hind legs like dinosaurs, report researchers.

They measured over three meters (9.8 feet) in length, the findings indicate.

The researchers first thought the similar-shaped fossilized footprints were from another ancient animal known as the pterosaurs, says Anthony Romilio, a paleontologist at the University of Queensland.

“The footprints measure around 24 centimeters [9.4 inches], suggesting the track-makers had legs about the same height as human adult legs.”

“At one site, the footprints were initially thought to be made by a giant bipedal pterosaur walking on the mudflat, we now understand that these were bipedal crocodile prints,” Romilio says.

“The footprints measure around 24 centimeters [9.4 inches], suggesting the track-makers had legs about the same height as human adult legs. These were long animals that we estimate were over three meters in length. And while footprints were everywhere on the site, there were no handprints.”

Soon, however, they soon found clues as to why there were no handprints.

Feet fossils from ancient bipedal crocodiles
Fossilized trackways made by ancient South Korean bipedal crocodiles. (Credit: Seul Mi Bae)

“Typical crocodiles walk in a squat stance and create trackways that are wide,” says Kyung Soo Kim, a professor from Chinju National University of Education.

“Oddly, our trackways are very narrow looking—more like a crocodile balancing on a tight-rope. When combined with the lack of any tail-drag marks, it became clear that these creatures were moving bipedally. They were moving in the same way as many dinosaurs, but the footprints were not made by dinosaurs,” Kim says.

A person stands near the ancient bipedal crocodile, it's body coming up to the person's waist
A reconstruction of ancient South Korean crocodile track-makers. (Credit: Anthony Romilio)

“Dinosaurs and their bird descendants walk on their toes. Crocodiles walk on the flat of their feet leaving clear heel impressions, like humans do.”

The researchers discovered the footprints, dated between 110-120 million years ago, after analyzing animal track sites in what is now known as South Korea.

They initially questioned the absence of hand impressions from the trackways, given that today’s typical crocodiles are “four-legged” or quadrupedal.

“Fossil crocodile tracks are quite rare in Asia, so finding an abundance of nearly one hundred footprints was extraordinary,” Romilio says.

“As an animal walks, the hind feet have the potential of stepping into the impression made by the hand and ‘over-printing’ it, but we find no evidence of this at these Korean sites,” he says.

“It isn’t due to poor preservation either, because these fossils are spectacular, they even have the fine details of the toe-pads and scales on their soles preserved.”

The research appears in Scientific Reports.

Source: University of Queensland