Fossil Pushes Back Date of Land-Animal Debut
A foot buried beneath Scottish soil for at least 345 million years pushes back the timeline for the appearance of the first four-legged creatures that spent their lives on dry land.
The specimen, 20 million years older than any known five-toed fossil, is just 10 millimeters across and comes from an unknown species. It’s one of a slew of new finds unearthed near rivers and coasts in Scotland and Canada helping to fill in a blank chapter in the evolution of life on land. Before about 360 million years ago, fishlike creatures could drag themselves along the shores of their watery homes. Then a massive extinction wiped out half of all vertebrate groups on the planet. But by about 345 million years ago, the planet teemed with a variety of creatures that lived on dry land. What happened to spur this exodus from water after the extinction has remained a mystery.