313-million-year-old track marks found in Grand Canyon

The fossilized tetrapod tracks, which came from the Manachaka Formation.
(Image: © Stephen Rowland/National Park Service)

Some 313 million years ago, a large lizard-like creature crawled up a coastal sand dune in what is now the Grand Canyon. Some time later, a light dew wetted the tracks cementing them in place and then a wind-blown sand buried them, preserving the animal’s clawed footprints for eons.

The paleontologists who studied the trackway say they are the oldest recorded vertebrate tracks in Grand Canyon National Park. Tetrapods, or four-legged beasts, left this set of tracks, along with another set imprinted a little later in time. The second set of footprints was laid down after some sand had accumulated in the first set, and the researchers said these prints could belong to the same species.

These ancestors of modern reptiles lived in the sand 250 million years before T. rexand they would have walked using a highly evolved gait.

Finding footprints

Allan Krill, a Norwegian geology professor, initially discovered the imprinted tracks in 2016 while leading his students along Bright Angel Trail on an annual field trip to the Grand Canyon. He noticed the fossilized footprints etched into a fallen boulder at the base of a canyon on the trail. Krill took photos of the prints and sent them to Steve Rowland, a geologist who often accompanied the Norwegian group on their trips.

Rowland and his team determined that the track-bearing boulder fell from a nearby cliff-exposure of the Manakacha Formation. “We were able to determine that it was from that area because we studied the nature of the rock, features such as its color and grain size,” he said. Knowing the origin of the rock also allowed researchers to date the tracks.

The size of the tracks suggest the creatures would have been about the size of a modern-day chuckwalla, 15 to 30 inches (or 40 to 80 centimeters) long, the researchers said.

A surprising gait

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