Health and Science Story

22 November 2008 18:30 BST

Scientists discover earliest animal footprints ever found

Scientists in the US have uncovered the footprints of animal from 570 million years ago.

The discovery pushes back the advent of more complex creatures on Earth by some 30 million years, a report published on Sunday claims.

The fossilised tracks, discovered in Nevada, show two parallel rows of small dots, each about 2mm in diameter, date from the Ediacaran period.

The Ediacaran preceded the Cambrian period, the time when most major groups of animals first evolved.

"We keep talking about the possibility of more complex animals in the Ediacaran -- soft corals, some arthropods, and flatworms - but the evidence has not been totally convincing," Loren Babcock, from the Ohio State University, said.

"But if you find evidence, like we did, of an animal with legs - an animal walking around - then that makes the possibility much more likely."

He added that he was "reasonably certain – not 100 per cent" that the fossil was made by a centipede-like arthropod of a leg-bearing worm.

"I expect that there will be a lot of scepticism," Mr Babcock said about the discovery.

"There should be. But I think it will cause some excitement. And it will probably cause some people to look harder at the rocks they already have. Sometimes it's just a matter of thinking differently about the same specimen."

In 2002, other researchers reported a similar fossil trail from Canada that dated back to the middle of the Cambrian period, about 520 million years ago. Another set of tracks found in south China date back to 540 million years ago.