I'm walking...



Big news in the vertebrate water-to-land arena. In the new issue of the journal Nature, researchers report the discovery of a Devonian trackway in a mountainous region in southern Poland. The tracks are those of a relatively large animal, with the 10" wide tracks indicating a body length of some 7-8 feet. There is no indication 0f "body drag", indicating an animal using it's forelimbs and hindlimbs to lift its body clear of the substrate. The find is very significant in our understanding of the transition of vertebrate life from strictly aquatic environments to a terrestrial existence. These fossil tracks, well preserved and securely dated, are from rocks 395 million years old, almost 20 million years earlier than the oldest known tetrapod fossils and are some 10 million years older than fossils of tetrapod-like fish such as the famous Tiktaalik. The tracks seem to have been made by an organism with front and hind limbs of similar size, walking in much the way that a modern salamander might. Also of interest is that the deposits indicate a marine environment, rather than fresh water. This runs counter of most current thought regarding tetrapod origins.

Nature provides a fascinating video, in which one of the researchers, Per Ahlberg of Uppsala University in Sweden, describes the find and discusses its significance. Ahlberg is one of leading researchers in the area of early tetrapod evolution, and calls the Nature paper the most important one that he has worked on. The take home message is that the find changes our perception of the type of animal that might have been making its way across a prehistoric mudflat almost 400 million years ago - instead of a fish using its lobed fins to drag its body along, we've got a walker.