Fossilised footprints hold clue to 'first steps'
The fossilised tracks of one of the first four-legged creatures to walk on land have been discovered in a disused quarry in southern Poland. The footprints date back 395 million years and are about 18 million years older than the oldest known "tetrapod" fossil.
Scientists said that the discovery sheds new light on one of the most important transitions in evolution: the point when fish with gills became air-breathing, terrestrial animals that walked on four legs.
The researchers have found several kinds of tracks made by animals of different sizes as they walked across the muddy floor of a marine lagoon, as well as individual footprints, some as large as 26cm wide, indicating a four-legged creature about 2.5 metres long.
According to a report in the journal 'Nature', the tracks have distinctive "hand" and "foot" prints and are arranged in a diagonal sequence with no evidence of the body being dragged along the ground, showing that the animal walked by flexing its raised body much like a modern-day lizard.
The tracks were found at the disused Zachelmie quarry in the Lysogory region of the Holy Cross Mountains in south-eastern Poland.
"The age is much earlier than any known tetrapods," said Professor Marek Narkiewicz of the Polish Geological Institute. The trackways were first discovered in 2004.
"It appeared so improbable that until 2007 nothing happened," Prof Narkiewicz said. With his wife, he worked out a more precise age for the rock formation using microscopic fossils, which suggested the trackways were made 395 million years ago, in the middle of the Devonian Period.
Some of the tracks are so detailed that they still have the imprints of toe-like digits. The diagonal stride indicates they could not have been made by the fins of a fish or any other animals known to be living at the time, the scientists said.(© Independent News Service)