The oldest recorded fossilized vertebrate tracks within Grand Canyon National Park were discovered following a cliff collapse, paleontological research has confirmed.
The tracks were discovered in 2016 when Norwegian geology professor, Allan Krill, was hiking with his students and noticed a boulder containing fossil footprints in plain view next to a trail.
Krill then sent photographs of the find to colleague Stephen Rowland, a paleontologist at the University of Nevada, Las Vegas.
“These are by far the oldest vertebrate tracks in the Grand Canyon, which is known for its abundant fossil tracks,” Rowland said in a press release.
“They are among the oldest tracks on Earth of shelled-egg-laying animals, such as reptiles, and the earliest evidence of vertebrate animals walking in sand dunes.”
The tracks recorded the passage of two separate animals; of particular interest to researchers is the gait displayed in one of the tracks.
The arrangement of footprints displays a lateral-sequence walk in which the legs on one side of the animal move in succession, the rear leg followed by the foreleg, alternating with the movement of the two legs on the opposite side.
“Living species of tetrapods, dogs and cats, for example, routinely use a lateral-sequence gait when they walk slowly,” Rowland said.
“The Bright Angel Trail tracks document the use of this gait very early in the history of vertebrate animals. We previously had no information about that.”
The footprints also document the earliest known utilization of sand dunes by vertebrate animals.
The boulder containing the historic find was determined to have fallen from a nearby cliff-exposure of the Manakacha Formation.
A research article of the fossilized tracks can be found online.