This painting shows what these dinosaurs may have looked like roaming the sand dunes of what is now Utah.Eleanor Kish, reproduced courtesy of the Canadian Museum of Nature
- A new sauropodomorph dinosaur has been discovered at Utah's red rocks.
- The dinosaur was buried, possibly while it was still alive, by a collapsing sand dune.
- The buried remains represent Utah's oldest most complete dinosaur.
During the Early Jurassic Period, a sand dune collapsed at Utah's red rocks with such force that it might have buried alive a plant-eating dinosaur, entombing and preserving the dinosaur upside-down for 185 million years, according to a new study published in the journal PLoS ONE.
The buried remains represent Utah's oldest most complete dinosaur. It has been named Seitaad ruessi, with the first word referring to a Navajo creation legend sand-desert monster that swallowed individuals in the dunes. The second honors artist and explorer Everett Ruess, who mysteriously disappeared at age 20 in the same region during the 1930s.
Ruess' body has never been found, but the fossils of the new dinosaur froze the animal's final moments. A CT scan reveals the dinosaur was missing a single toe and a lower leg bone, suggesting that it either died and was shortly thereafter engulfed by a collapsing sand dune, or was buried alive.
"If Seitaad were alive when the sand dune collapsed, it would have felt itself sliding, followed by darkness and a crushing weight, knocking the wind out of it, pressing in on its chest and not allowing it to take another breath," co-author Mark Loewen, a paleontologist at the Utah Museum of Natural History and an instructor in the Department of Geology and Geophysics at the University of Utah, told Discovery News. "It would be a rough way to die with a mouth full of sand in the darkness."
He and colleague Joseph Sertich analyzed the fossils and determined that the dinosaur was one of the first sauropodomorphs from North America. It was related to dinosaurs from southern South America and southern Africa. Sauropodomorphs later evolved to become enormous sauropods.
"Presumably, the sauropods evolved large body size as a strategy to deter predators," Loewen said. "No one will mess with a healthy animal that weighs 35 tons."
Seitaad was a more modestly sized dinosaur, however, standing about 4 feet tall at the hips and measuring 15 feet long. It weighed around 200 pounds, possessed a large, curved "thumb" claw. Seitaad also had a long neck and tail, and could walk on two or four legs.
All animals previously found at the site, near Bluff, Utah, were relatively small, probably because the desert habitat didn't support much vegetation. Those animals include relatives of modern crocodiles, mammalian ancestors called tritylodonts and two carnivorous dinosaurs, both of which probably preyed upon the sauropodomorph.
Seitaad was remarkably well preserved in the Navajo Sandstone, but its head and parts of its neck and tail were lost due to erosion over time. The researchers, however, believe Native Americans living 500 feet above in an ancestral Puebloan (Anasazi) cliff dwelling 1,000 years ago could see the now-missing dinosaur bones.
"Native Americans living in the region would certainly have recognized the bones of Seitaad as animal bones," Loewen explained. "Many people who eat meat off the bone, rather than processed and packaged in a grocery store, have a basic knowledge of the skeleton of animals."
"(The bones) were a beautiful white in the pink sandstone when we first saw them," he noted. Loewen added that the early Native American cliff dwellers even had "a slab with a dinosaur track incorporated into the window sill, perfectly centered."
"I'm confident that the person who built this dwelling had awareness and appreciation for the fossils preserved in the Four Corners region," he said.
Sudden avalanches of sand are thought to have buried dinosaurs elsewhere, such as at the Gobi Desert. David Loope of the University of Nebraska and his colleagues discovered remains there of numerous dinosaurs and other animals that were killed swiftly and buried before their bones could be scavenged or destroyed by the elements.