Fossilized footprints discovered in Grand Canyon National Park were confirmed by paleontologists on Friday to be the oldest recorded tracks of their kind.
The tracks were first found inside a boulder by Norwegian geology professor Allan Krill and his students in 2016, but now researchers have found that they're the oldest in existence — around 313 million years old, give or take half a million years.
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"These are by far the oldest vertebrate tracks in Grand Canyon, which is known for its abundant fossil tracks," said Stephen Rowland, a paleontologist at the University of Nevada, Las Vegas. "They are among the oldest tracks on Earth of shelled-egg-laying animals, such as reptiles.
They're also the earliest evidence of vertebrates walking on sand dunes.
The tracks show two animals walking in a "lateral sequence walk" — meaning the two legs on each side move in succession, with the rear leg first and the front leg following (the same way cats and dogs walk).
"[The] tracks document the use of this gait very early in the history of vertebrate animals. We previously had no information about that," Rowland said.
The research was published in the PLoS ONE journal.
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