Fossil of earth's oldest footprints found

The oldest-known tracks of a creature apparently using legs have been discovered in rock dated to 570 million years ago in what was once a shallow sea in Nevada.

Scientists think land beasts evolved from ancient creatures that left the sea and evolved lungs and legs. If the new finding is real - the discoverer says will fuel skepticism - it pushes the advent of walking back 30 million years earlier than any previous solid finding.

The aquatic creature left its "footprints" as two parallel rows of small dots, each about 2 millimeters in diameter.

The tracks were made during what is called the Ediacaran period, which preceded the Cambrian period, the time when most major groups of animals first evolved. Scientists had once thought only microbes and simple multicellular animals that existed prior to the Cambrian, but that notion is changing, said Ohio State University Professor Loren Babcock.

Little can be gleaned about what sort of creature it was, but Babcock "reasonably certain - not 100 percent" that it was an arthropod, such as one resembling a centipede or millipede, or by a leg-bearing worm. It might have been about one as wide as a pencil and may have had multiple, spindly legs.

"I expect that there will be a lot of skepticism," 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."