A rock tumble at the Grand Canyon revealed fossil footprints that researchers say are among the oldest in the park.

Fossilized animal tracks discovered in the Grand Canyon were likely left by a reptile some 313 million years ago, among the oldest found on Earth, a UNLV professor said.

Finding fossil footprints at the Grand Canyon isn’t particularly unusual. The expansive stretch of red rock is home to an array of formations containing preserved remains of the past.

Geologist Allan Krill was hiking along the Grand Canyon National Park’s Bright Angel Trail with a group of students in 2016 when he spotted it: a fallen boulder lying just off the side of the trail, with curious markings that resembled footprints. Krill, who was visiting the University of Nevada, Las Vegas (UNLV) from Norway, sent photos of his find to an old friend and colleague, Stephen Rowland, a UNLV paleontologist.

A new research paper led by paleontologist Steve Rowland at the University of Nevada, Las Vegas analyzes this chance find of two sets of footprints (also called trackways) on the same rock that are potentially both from the same unknown species.

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

A rock tumble at the Grand Canyon revealed fossil footprints that researchers say are among the oldest in the park.

Footprints found on a boulder which had stood in plain view of tourists in the Grand Canyon actually date from an astonishing 313 million years ago, researchers in America have confirmed.