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Fossil tracks push back the invasion of land by 18 million years

A set of 395 million year old fossil tracks suggest that four-legged animals – tetrapods – were walking the Earth 18 million years earlier than we thought. The discovery could radically change what we know about why, where and how animals invaded the land from the sea.

By Ed Yong

PUBLISHED January 6, 2010

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 walking on legs. These include Panderichthys, a fish with a large tetrapod-like head and a muscular pair of front fins. Tiktaalik expanded on these themes. Its head could turn about a solid neck. Its limbs had the fin rays of its fishy predecessors but clear wrist bones and basic fingers too. Tiktaalik could support itself on strong shoulder bones,...

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Fossil tracks push back the invasion of land by 18 million years

A set of 395 million year old fossil tracks suggest that four-legged animals – tetrapods – were walking the Earth 18 million years earlier than we thought. The discovery could radically change what we know about why, where and how animals invaded the land from the sea.

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