New Research Suggests That Early Amphibians Could Not Walk Properly

The CT reconstruction of Ichthyostega

In 1932, a team of palaeontologists excavating in East Greenland recovered some fossils of a strange tetrapod. Analysis revealed that it was an amphibian, and at the time, was the oldest known specimen. Fossils of tetrapod-like fish had been found as early as the 19th century. Yet this find caused a stir in the scientific community when its importance came to light: palaeontologists had a link from the other end of the chain, detailing its origins on land.

The creature in question, which was named Ichthyostega, looked rather like a cross between a newt and a crocodile. It was no more than a metre in length, had a set of heavy jaws filled with sharp teeth, a squat body and thick legs. While its feet where small and webbed, and had a long phlange along the length of its tail, many thought that it had the ability to walk on the land, as well as navigate through reed beds, swamps and flooded marshes where its ancestors dwelled.

Yet early models of Ichthyostega, made from wax and plastic, were based on speculation. Now, Dr Jenny Clack, professor at the University of Cambridge and arguably the most well-known, early tetrapod palaeontologist, and Professor John. R. Hutchinson from the UK's Royal Veterinary College, believe that these early interpretations were wrong. They took well preserved fossils of Ichthyostega and, using computed tomography (CT) scans, built up new 3D manipulable models of the creature.

As the scans were able to reconstruct accurately even the tiniest bones of the 360 million year old fossils, these new models gave Clack and Hutchinson the best idea yet as to how this creature moved, how far it could move its limbs and with what kind of muscle power. They concluded that Ichthyostega would have been unable to rotate its limbs sufficiently to walk actively across dry land, but would have been able to drag itself along enough to cross from one water-way to another.