New dinosaur species found in Utah

SALT LAKE CITY — The fossilized bones of a creature the early Navajo called the "sand desert monster" have been confirmed as those of a new species of plant-eating dinosaur that scientists say roamed the red rock cliffs of southeastern Utah some 185 million years ago.

Seitaad ruessi (SAY-eet-AWD ROO-ess-EYE) is a rare and important find because of where it was found and because it fills a genealogical gap in the family history of the giant, long-necked, herbivorous sauropod dinosaurs that populated the later Jurassic, according to a report appearing in Wednesday's edition of PLoS ONE, the online open-access journal of the Public Library of Science.

Authors Joseph Sertich, a former University of Utah master's degree student, and Mark Loewen, a paleontologist at the Utah Museum of Natural History, report that Seitaad ruessi is a much smaller, much earlier member of the sauropodomorphs family that evolved into the giant and abundant herbivores that are well-documented elsewhere in Utah.

The animal had a body a little larger than a modern rangeland sheep but had a very long neck and tail and leaf-shaped teeth. It could walk on its hind legs as well as on all fours, Loewen said.

"We know from geologic evidence that seasonal rainstorms like today's summer monsoons in the tropics provided much of the moisture in what was a sand sea, filling ponds and other low spots between the dunes and providing plants the dinosaur lived on," Loewen said.

The mostly intact skeleton was discovered in 2004 by Joe Pachak, a local historian and artist, while hiking in the Comb Ridge area near Bluff, San Juan County. Prior to that, the sandstone had revealed only some footprints; a few fossil remains of relatively small animals, including a carnivorous dinosaur; crocodile relatives; and proto-mammals called tritylodonts. Seitaad was likely the largest herbivore during that time period, according to the study report.

The dinosaur was apparently buried in a sand dune that collapsed around it. The Navajo legend of how the world was created includes a monster in the desert ("Seit'aad") that swallowed its victims in sand dunes.

The missing parts of the skeleton, including the head, were lost to erosion during the past 1,000 years but were almost certainly visible to Native Americans living on the cliff just above where the fossilized remains were found, Loewen said.

The "ruessi" in the name comes from another legend, a more modern one about a biped human poet and explorer "swallowed" in the same area in 1934 at age 20, but whose remains have never been found: Everett Ruess.

There's much more likely to be found in Navajo sandstone, the rock that covers major portions of Utah and is exposed in many national parks and monuments throughout the Colorado Plateau, Sertich said.

e-mail: jthalman@desnews.com