Evidence that four-legged vertebrates walked on Earth some 10 million years earlier than previously believed could force a radical rethink of where they evolved, as well as when.

Tetrapod footprints dating back 397 million years have been discovered in the Świętokrzyskie mountains in southern Poland in what was, at the time they were made, a seashore. All previous fossil evidence for these earliest known four-limbed vertebrates has been found in river deltas and lakes.

"Our discovery suggests that the current scientific consensus is mistaken not only about when the first tetrapods evolved, but also about where they evolved," says Grzegorz Niedźwiedzki of the Department of Palaeobiology and Evolution at the University of Warsaw in Poland, who discovered the footprints in 2002 in an old quarry near the town of Kielce.(New Scientist)