A new study based on fossilized footprints suggests a prehistoric relative of modern crocodiles walked on two hind legs.
The study, published Thursday in the journal Scientific Reports, describes how ancient fossilized footprints discovered in South Korea had originally been thought to belong to a pterosaur — a flying dinosaur — that had been walking on two legs.
But further analysis of the prints suggests that they actually belonged to a bipedal crocodile, a creature that walked on two legs because it was semi-adapted to land.
This is the first evidence from this time period of a bipedal crocodylomorph, a branching, diverse group of animals that includes crocodilians and their extinct relatives. The researchers named the new species Batrachopus grandis.
The footprints were 18 to 24 centimeters long, suggesting that the creatures’ bodies were almost 3 meters long. They seem to have been left only by the back limbs, showing a clear heel-to-toe walking pattern.
The well-preserved fossils, discovered in South Korea's Jinju Formation, date to the lower Cretaceous period, which spanned 145 million to 105 million years ago. A 2015 study describes at least one instance of a bipedal crocodylomorph believed to have lived in the southeastern U.S. state of North Carolina 230 million years ago.