https://apnews.com/b2a31410387fe8de3a97a120ec510907

FLAGSTAFF, Ariz. (AP) — It's something like a modern-day chuckwalla, side-stepping sand dunes on an island in what now is Grand Canyon National Park.

That's how Steve Rowland, a professor emeritus of geology at the University of Nevada, Las Vegas, interprets fossil footprints that were revealed in a rock fall near a popular Grand Canyon hiking trail. He estimates they're 313 million years old, give or take a half-million years.