Animals walked using legs at least 30 million years earlier than thought

October 6th, 2008 - 12:32 pm ICT by ANI  

Washington, Oct 6 (ANI): The fossilized trail of an aquatic creature has suggested that animals walked using legs at least 30 million years earlier than had been thought.

Scientists once thought that it was primarily microbes and simple multicellular animals that existed prior to the Cambrian, but that notion is changing, according to Loren Babcock, professor of earth sciences at Ohio State University.

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, he 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.

Babcock was surveying rocks in the mountains near Goldfield, Nevada, with Hollingsworth in 2000 when he found the tracks.

This was truly an accidental discovery. We came on an outcrop that looked like it crossed the Precambrian-Cambrian boundary, so we stopped to take a look at it. We just sat down and started flipping rocks over. We were there less than an hour when I saw it, he said.

The creature must have stepped lightly onto the soft marine sediment, because its legs only pressed shallow pinpoints into that long-ago sea bed.

But, when Babcock flipped over the rock containing those tracks, the low-angle sunlight cast the dots in crisp shadow.

He immediately suspected that the tracks were made by an arthropod, such as one resembling a centipede or millipede, or by a leg-bearing worm.

He couldnt be certain of the length of the creature, or the number of legs it had. But, judging from the tracks, he guessed that it carried its centimeter-wide body on many spindly legs.

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.

At approximately 570 million years old, this new fossil not only provides the earliest suggestion of animals walking on legs, but it also shows that complex animals were alive on earth before the Cambrian.

Not many macroscopic fossils exist from that time because soft-bodied creatures are not normally preserved.

The shallow sea covering western Nevada 570 million years ago would have been a good site for exceptional preservation.

The sediment surface was probably bound together by a microbial mat - a cohesive carpet of bacteria and sediment grains.

A creatures tracks could have been readily preserved when the animal pressed its legs into the sediment. (ANI)

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