Tiny Footprints, Big Discovery

It might otherwise go unnoticed except for the 28 indentations — sloping footprints left behind by a small, reptile-like creature about 310 million years ago — that cover the rock’s expansive surface.

“It’s the oldest trackway ever discovered in the Grand Canyon in an interval of rocks that nobody thought would have trackways in it, and they’re among the earliest reptile tracks on earth,” said Steve Rowland, UNLV professor of geology who is studying the fossil trackways.

“One reason I’ve proposed is that the animal was walking in a very strong wind, and the wind was blowing it sideways,” he said.

Another possibility is that the slope was too steep, and the animal sidestepped as it climbed the sand dune. Or, Rowland said, the animal was fighting with another creature, or engaged in a mating ritual.

“I don’t know if we’ll be able to rigorously choose between those possibilities,” he said.

He plans to publish his findings along with geologist Mario Caputo of San Diego State University in January. Rowland also hopes that the boulder is soon placed in the geology museum at the Grand Canyon National Park for both scientific and interpretive purposes.

Meanwhile, Rowland said that the footprints could belong to a reptile species that has never yet been discovered.

“It absolutely could be that whoever was the trackmaker, his or her bones have never been recorded,” Rowland said.