BILLINGS, Mont. (AP) — Researchers have formally measured and described three dinosaur tracks embedded in sandstone near Glenrock in central Wyoming.

Sean Smith and Scott Persons have authored a research paper on the rare footprints that has now been published in the peer-reviewed journal.

The first three-toed track was noticed in the sandstone bed of a ravine in 2000. Two more tracks from the same dinosaur were revealed nearby.

The tracks were made about 66 million years ago.

Persons says the Glenrock site is particularly valuable because researchers can measure stride lengths.