They were named oviraptors, meaning "egg thieves," because they were originally thought to prey on the dinosaur eggs near which their fossils were often found. More recent evidence suggests these eggs belonged to their own nests.
"Hagryphus wouldn't have been capable of attacking a large animal, so perhaps it took prey such as small mammals and small lizards and maybe supplemented its diet with fruits, seeds, and nuts," Zanno said.
Zanno and Sampson say the Utah fossil almost doubles the known range of oviraptors in North America.
Oviraptor fossils have been found throughout a large area of Asia. But they were thought to have inhabited only the northern region of North America. Their fossils have been found in Montana and South Dakota as well as Alberta, Canada.
At the time they lived, the central part of North America was flooded by rising sea levels caused by a warming climate.
The researchers say they're perplexed by the fact that the new species was twice the size of the other known oviraptors that lived on what was then an isolated landmass.
"We don't have any evidence of a huge mountain range or an ocean that separated the north and the south [of the landmass], so it's rather surprising to find different-sized dinosaurs up and down this strip of land," Zanno said.
It could be that these species were filling different ecological niches, Zanno added"in other words, eating something different or living in a different habitat. Or perhaps Hagryphus had access to more land to roam or live in."
The new dinosaur was found in the Grand Staircase-Escalante National Monument, a 1.9-million-acre (690,000-hectare) protected area in southern Utah managed by the U.S. Bureau of Land Management.
The area's remote and austere landscape boasts fossil-rich rock formations that researchers say preserve one of the world's most complete records of prehistoric life near the end of the dinosaur age.
"Due to the extremely rugged nature of the terrain, this region was the last major area within the lower 48 [United] States to be formally mapped," said Scott Sampson, chief curator at the Utah Museum of Natural History in Salt Lake City.
"For the same reason, it now represents an untappedand perhaps the last:major dinosaur graveyard in this country to be explored," he added.
Recent fossil hunts by University of Utah researchers have already uncovered three other previously unknown types of dinosaurs.
These include meat-eating tyrannosaurs, duckbilled dinosaurs, and horned dinosaurs that have yet to be named, Zanno says.
"The whole ecosystem appears to be new to sciencewe have three new species in the pipeline," she added.
"The region is a kind of last Eden of dinosaur paleontology in North America."
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