Batrachopus trackmaker to human scale. Credit: Anthony Romilio, The University of Queensland, Brisbane, Australia.

Ancient crocodiles walked on two legs like dinosaurs

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Ancient footprints found in South Korea might have belonged to a two-legged croc, according to Aussie and international researchers, and this finding might reshape previous research into ancient reptiles. The well-preserved 18-24cm footprints were previously thought to have been made by giant pterosaurs walking on two legs to protect their wings, but the authors argue they are more likely from crocodylomorphs, ancestors to modern-day crocodiles and alligators. The size of the footprints indicate a body length of up to three metres, while the skin traces and clear impressions suggest heel-toe walking, researchers say.

Journal/conference: Scientific Reports

Link to research (DOI): 10.1038/s41598-020-66008-7

Organisation/s: The University of Queensland

Funder: No information provided.

Media release

From: The University of Queensland

An international research team has been stunned to discover that some species of ancient crocodiles walked on their two hind legs like dinosaurs and measured over three metres in length.

University of Queensland palaeontologist Dr Anthony Romilio said the researchers first thought the similar-shaped fossilised footprints were from another ancient animal known as the pterosaurs.

“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,” Dr Romilio said.

“The footprints measure around 24 centimetres, suggesting the track-makers had legs about the same height as human adult legs.

“These were long animals that we estimate were over three metres in length.

“And while footprints were everywhere on the site, there were no handprints.”

The research team, led by Professor Kyung Soo Kim from Chinju National University of Education, soon found clues as to why there were no handprints.

“Typical crocodiles walk in a squat stance and create trackways that are wide,” Professor Kim said.

“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.

“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 footprints dated between 110–120 million years ago and were discovered after analysing animal track sites in what is now known as South Korea.

Researchers 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,” Dr Romilio said.

“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.

“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.”

This research has been published in Scientific Reports (DOI: 10.1038/s41598-020-66008-7).

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    Trackways at the Sacheon Jahye-ri site.

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    Attribution: Kyung Soo Kim, Chinju National University of Education, Kyungnam, South Korea.

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    Trackways at the Sacheon Jahye-ri site.

    File size: 2.1 MB

    Attribution: Kyung Soo Kim, Chinju National University of Education, Kyungnam, South Korea.

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    Image 3:

    Batrachopus trackmaker to human scale.

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    Attribution: Anthony Romilio, The University of Queensland, Brisbane, Australia.

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    Reconstruction of Batrachopus trackmaker from the Lower Cretaceous Jinju Formation of South Korea .

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    Attribution: Anthony Romilio, The University of Queensland, Brisbane, Australia.

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    Photographs of well-preserved in situ Batrachopus grandis ichnosp. nov. track impressions.

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    Attribution: Kyung Soo Kim, Chinju National University of Education, Kyungnam, South Korea.

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    Photos and 3D images of track casts.

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    Attribution: Kyung Soo Kim, Chinju Natioal University of Education, Kyungnam, South Korea.

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