Scientists have been stunned to discover that some ancient crocodiles may have moved on two feet.
The evidence comes from beautifully preserved fossil footprints in South Korea.
Almost a hundred of these 1
The international team behind the discovery says it will probably challenge our perception of crocodiles.
“People tend to think of crocodiles as animals that don’t do much; they just lie around all day on the Nile beach or next to rivers in Costa Rica. No one automatically thinks I’m wondering what this is [creature] would be as if it were twofold and could run like an ostrich or one T Rex, “Martin Lockley, an emeritus professor at the University of Colorado, USA, told BBC News.
The study will certainly provoke a lively debate. Not all researchers necessarily accept the team’s interpretation.
Prof Lockley and colleagues have assigned the name Batrachopus grandis to the animal that made the traces, although no physical remains of it have yet been revealed.
Recognition of the creature’s existence depends only on fossil pressure itself. These look very similar in shape, albeit much larger, to those made of Batrachopus crocs that lived tens of millions of years earlier in Jurassic. Except the older animals were obviously quadrupled – they went on four.
A two-fold interpretation of the new Korean trace fossils is the only explanation, says Prof Lockley.
“We can see all the numbers, all the ridges in the skin – just as if you were looking at your hands,” he explained. “They put one foot in front of another; they could pass a sobriety test that goes on a straight line. And there are no front footprints.”
The depth of the heel impression also supports the idea of a more upright position, says team leader Prof Kyung Soo Kim of South Korea’s Chinju National University of Education.
“Our paths are very narrow – more like a crocodile balancing on a tight rope,” he commented.
“When combined with the absence of tail markings, it became clear that these creatures were moving two-way.
“They moved in the same way as many dinosaurs, but the footprints were not made of dinosaurs. Dinosaurs and their offspring are on their toes.
“Crocodiles get on their feet and leave clear health impressions, as people do.”
For Prof Lockley, the new prints also help to interpret a South Korean runway that he and other colleagues described eight years ago. In 2012, this group believed that a set of less defined and slightly younger features could have been provided by giant versions of the flying reptiles known as pterosaurs.
These animals are widely recognized to have interfered with their feet and hands on the ground – rather like a bat. However, this enigmatic path had looked like bipedal – perhaps the result of a pterosaur that waded through water with only its feet in contact with the sediment.
Prof Lockley now believes that this course was also very likely a bipedal Batrachopus.
Prof Phil Manning from the University of Manchester, UK, was not part of the discovery team. As a fossil web specialist himself, he described the printouts as “very interesting” and welcomed their publication to begin a discussion – but he doubted the interpretation.
“For me, the tracks just don’t fit the overall geometry of a crocodilian and what it can produce,” he told BBC News.
“Watch all the videos of live hooks and rotation of their feet as they gallop: it’s outward, not inward toward the center line of the track. Just from their orientation, it looks more like a kind of dinosaur tracker to me But whether it’s a hook – unfortunately we do not have the fossil bones to tell. “
The tracks to Batrachopus grandis is reported in the journal Scientific Reports.