Around 395 million years ago, a group of four-legged animals strode across a Polish coast. These large, amphibious creatures were among the first invaders of the land, the first animals with true legs that could walk across solid ground. With sprawling gaits and tails held high, they took pioneering footsteps. Their tracks eventually fossilised and their recent discovery yields a big surprise that could rewrite what we know about the invasion of land. These animals were walking around 18 million years earlier than expected.

The evolution of four-legged creatures – tetrapods – is one of the most evocative in life’s history. It has been illustrated by a series of beautiful fossils that vividly show the transition from swimming with fins to