World's Oldest Footprints Found in Nevada?

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"It's like taking a dull pencil point and poking it into sediment," he said, noting that such a description may not be so far from how the marks were actually made.

About 570 million years ago, the area was covered by a shallow sea. The water had a mat-like surface made of sediment grains that were held together by a cohesive network of bacteria and fungi, which would have easily preserved animal tracks.

The tracks were determined to have been made in the Ediacaran period by comparing the "footprints" layer to previously dated layers with similar features.

"There is nothing we can use to [directly] obtain numerical age date," said Babcock, who acknowledges the findings could be hard for some to swallow.

"If everyone accepted it right off the bat, I'd be shocked," he said.

"Paired Rows of Dots"

Precambrian paleontologist Nick Butterfield said he was "deeply skeptical," about the conclusions drawn.

"From the description—paired rows of dots—it just doesn't sound like a trackway," the University of Cambridge scientist said in email.

"Centipedes and their ilk shuffle along and leave continuous traces in soft (sub-aerially exposed) sediments—they don't carefully step ahead, lifting each foot out of the mud to place it exactly in a previously made footprint," he said.

The probability the tracks were made in an underwater environment is even lower, he said.

"With a specific gravity essentially the same as water/mud, small aquatic invertebrates simply don't sink into the mud and don't leave footprints."

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