Dinosaur prints have U. scientists sorting clues

There's probably no extinct creatures as long gone as the dinosaurs, yet they're still regularly showing up in remnants of one version or another to provide scientists clues that usually lead to more clues that sometimes significantly alter what we think we know about them.

Since dinosaurs were first described by science in the 19th century and the discipline of paleontology was started, petrified bones show up now and then, tracks have been uncovered worldwide, as well as dino-doo. That's probably because the beasts didn't just walk the earth, they pretty much owned it, that is until the landmasses split, about the same time the dinosaurs also did.

Here we are 190 million years later, and no one's ever found a live one, but they certainly left a lot of tracks behind showing that they were alive and well at one time here in Utah. Another big collection of footprints — this one remarkably concentrated and appearing to be a collection of footprints on top of footprints — is adding more evidence that Utah's southeastern border area with Arizona was a veritable stomping ground or at least a regularly populated terrain that back then could have been a watering hole oasis in a desert bigger than today's Sahara.

The wilderness area where the three-quarter-acre tracks site is located is noticeably lacking in water. But that's just one of the changes the landscape has undergone over the eons, said Marjorie Chan, professor and chair of geology and geophysics at the University of Utah, in announcing the find.

The area is part of the Paria Canyon-Vermilion Cliffs National Monument today. In the early Jurassic period, it was a full-on desert, like the Sahara today, but with much larger dunes and sand that covered Utah, Wyoming, Colorado, New Mexico, Arizona and Nevada. The particular area is trampled with thousands of tracks, which look more like sandstone divots than footprints, indicating it was likely a watering hole.

Geologically, the trampled surface is more than a wet pond remnant of those days, "but possibly a record of global climate shift from dry to wetter conditions." The surface is a key factor in the find because the study is the first known publication to identify the impressions as dinosaur footprints on trample surface, Chan said.

After the dinosaurs left their prints, the surface was covered by shifting dunes, which eventually hardened into sandstone. The sandstone has eroded away, exposing the tracks, said Winston Seiler, who studied the site for a master's thesis. The trample surface "helps paint a picture of what it was like to live back then."