Grand Canyon fossilized tracks suggest that reptile ancestors were adapted to the land

313 million years ago, a large lizard-like creature crawled on a coastal sand dune that is now Grand Canyon. After some time, a light dew moistened the tracks with cement in place and then the wind blowing sand buried them, preserving the animal’s claw marks for eons.

Paleontologists who study the trackway say they are the oldest recorded vertebrate tracks in Grand Canyon National Park. Tetrapods or four-legged animals left this set of tracks, with another set imprinted after a while. The second set of footprints was placed down after some sand deposited in the first set, and the researchers said that these prints may be of the same species.