They Walked! Prehistoric Crocodiles Were Bipedal

Tracks found in South Korea have been identified as belonging to ancient crocodylomorphs that walked on two legs. (Image: Screenshot / YouTube)

If crocodiles scare you already, then evidence of their ancient ancestors walking on two legs is guaranteed to terrify you.

In a recent paper published by Scientific Reports, crocodylomorph tracks were discussed. The analysis indicates a large possibility that the crocodile’s ancestors walked on their hind legs much like the T-rex.

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The large 10-foot-long crocodile relatives walked on Earth approximately 120 million years ago in what is now South Korea. Though no fossilized bones have been found, stones have been discovered with ancient footprints — one actually has a skin impression on it — at the Sacheon Jahye-ri track site, in the west of Sacheon City in South Gyeongsang Province.

Tracing the footprints

The footprints were seemingly left by the back limbs, strongly suggesting that the crocodile’s ancestors had a heel-to-toe walking pattern. With tracks sizing up to 9.5 inches long, the researchers think that these ancient crocodiles had legs about the same height as an adult human’s legs.

The measurement also had the researchers assume the size of the ancient animal to be nearly 10 feet long. The discovery dates back to the late cretaceous epoch, which covers 145 million to 105 million years ago.

Korean researchers transferred the trackways to a lab after the initial discovery. Then, lead paper author, Kyung Soo Kim, a paleoecologist at the Chinju National University of Education in South Korea, invited Martin Lockley, professor emeritus of geology at the University of Colorado Denver and co-researcher of the study, to examine the find and give his impressions of the discovery.

Analyzing the clues

The team initially speculated that these fossilized tracks belonged to a pterosaur, a flying dinosaur. But Lockley has worked on similar studies in the past — crocodile prints from the Jurassic period in particular.

(Image: Screenshot / YouTube)
The team initially speculated that the fossilized tracks belonged to a pterosaur, a flying dinosaur. (Image: Screenshot / YouTube)

In comparison with the prints at the Sacheon Jahye-ri track site, the size of the crocodile tracks that the researcher previously studied were minuscule: only about 1 inch. However, the similarities between those tracks and the new ones were striking. Lockley knew immediately that these ancient prints were of a Batrachopus specimen.

There were hints that these tracks were never really of the pterosaurs. For example, the flying dinosaurs, even with their wings, might have walked on all fours. Researchers found no handprints or wing prints at the track site.

Pads and joint impressions that seem to belong to crocodiles are evident, on the other hand. And finally, the skin impression of one of the heels allowed researchers to piece together the mystery. Further analysis later confirmed the current conclusion.

Martin Lockley told Live Science magazine that this is the first proof pointing to the existence of some bipedal giant crocodiles from the cretaceous period that were similar to carnivorous dinosaurs.

Crodcodylomorph is a group of archosaurs that includes crocodiles — large, semiaquatic, and carnivorous reptiles — and their extinct relatives. The researchers named the new species Batrachopus grandis.

(Image: Goutham89 via wikimedia CC BY-SA 4.0)
Crodcodylomorph is a group of archosaurs that includes crocodiles. (Image: Goutham89 via wikimedia CC BY-SA 4.0)

Reanalyzing previous discoveries

This new development calls for a possible re-examination of pterosaur footprints in Gain-ri, another South Korean site. There’s a possibility that the animals behind the Gain-ri tracks were smaller Batrachopus carefully treading mud.

In fact, University of Bristol pterosaur expert Liz Martin-Silverstone agrees that the prehistoric discovery at Sacheon Jahye-ri track site looks much more crocodilian than what would have been left by pterosaurs. And she noted that, upon reexamination, previously described bipedal pterosaur trackways have actually proven to have been made by the crocodile’s cretacean ancestors.

Mistaken identities can happen when it comes to prehistoric footprint analysis. “The tracks produced can change significantly, depending on things like what the animal was doing at the time the track was made, the nature of the substrate, where the center of gravity was, and what type of gait it had,” Martin-Silverstone explains (Scientific American).

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