U.S. scientists have identified a new dinosaur species found to have populated the Grand Staircase-Escalante National Monument area in Utah.

"It was one of the most robust duck-billed dinosaurs ever," said Utah Museum of Natural History paleontologist Terry Gates. "It was a monster."

Researchers from the museum, the national monument and California's Raymond Alf Museum of Paleontology unearthed fossils of the ancient plant-eater from the rocks of the Kaiparowits Formation.

The creature -- named Gryposaurus monumentensis -- was a duck-billed dinosaur dating to the Late Cretaceous Period 75 million years ago.

"Gryposaurus monumentensis is probably the largest dinosaur in the 75-million-year-old Kaiparowits fossil ecosystem," said Alan Titus, paleontologist for the national monument.

Scott Sampson, another museum paleontologist, emphasized the massively built skull and skeleton by referring to the animal as the "Arnold Schwarzenegger of duck-billed dinosaurs."

The scientists said the dinosaur had more than 300 teeth available, but with numerous replacement teeth stored in its jawbone it might may have carried more than 800 teeth. It is estimated to have grown to about 30 feet in length.

The discovery is reported in the Zoological Journal of the Linnean Society.