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Utah Department of Natural Resources
Don DeBlieux, Utah Geological Survey, discovered the skeleton of Iguanacolossus at a site near the town of Green River.

SALT LAKE CITY — Utah can now add two more species of dinosaurs to its inventory — a pair of beaked herbivores that roamed along slow-moving rivers in southeastern Utah more than 124 million years ago.

Called "iguanodonts," the skeletons were discovered at a site near the town of Green River and at an area north of Arches National Park.

The skeletons of Hippodraco and Iguanacolossus were discovered by Andrew Milner (St. George Dinosaur Discovery Site) and Don DeBlieux (Utah Geological Survey), respectively. Both skeletons are part of the collections of the Utah Museum of Natural History and the skull of Hippodraco will be featured in the paleontology exhibit in the new museum next year.

Found all over the world, the fossils of iguanodonts are particularly abundant in Europe and east-central Asia. Until recently, their fossil record in North American was patchy.

Scientists say, however, that the Utah discovery of the two new specimens from the early cretaceous period offers new information.

The name of one of the new dinosaurs, Hippodraco scutodens, means horse-dragon, referencing the long, low shape of the animal's skull that resembles that of a horse.

The second part of the name references the oblong, shield-shaped tooth crowns in the animal's jaws. The skeleton comes from an animal that is about 15 feet long, although scientists do not believe it was fully grown. The dinosaur lived approximately 124 million years ago, the same time as the Utahraptor.

The other new iguanodont, Iguanacolossus fortis, received its name because its teeth resemble those of the iguana lizard.

The name Iguanacolossus combines "iguana" with the Latin colossus, which refers to immense statues such as the famous Colossus of Rhodes. The second part of the name, fortis, is a Latin word for "mighty". The name Iguanacolossus fortis describes the size of the dinosaur, which was about 30 feet in length.

The rocks in which the skeletons were entombed indicate the area in Utah at the time had a dry climate and landscape that featured small lakes and rivers.

Both sites were excavated by staff of the Utah Geological Survey and volunteers of the Utah Friends of Paleontology led by Utah State Paleontologist James Kirkland as part of his research on the Cedar Mountain Formation.

After years of meticulous work, the skeletons were removed from the rock for further study. The task of describing these new dinosaurs fell to Andrew McDonald, a doctoral candidate at the University of Pennsylvania, under the supervision of Peter Dodson.

McDonald's work was part of a broader project investigating the evolution of iguanodonts.

McDonald, Kirkland, and colleagues have published their findings in the online journal PLoS One, which can be accessed at dx.plos.org

e-mail: amyjoi@desnews.com