Dinosaur Fossils Helicoptered Out of Southern Utah

“It was one of the most robust duck-billed dinosaurs ever,” said Utah Museum of Natural History paleontologist Terry Gates of Gryposaurus, which means hook-beaked lizard. “It was a monster.”

Gryposaurus monumentensis

Art by Larry Felder

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

With its robust jaws, this dinosaur likely mowed down nearly every plant in its path.

Skull of Gryposaurus

(Credit: Utah Museum of Natural History)

Around 75 million years ago, southern Utah differed dramatically from today’s arid desert and redrock country. During much of the Late Cretaceous, a shallow sea split North America down the middle, dividing the continent into eastern and western landmasses.

G. monumentensis and its fellow dinosaurs lived in a narrow strip of land sandwiched between the seaway to the east and rising mountains to the west. Due in large part to the presence of the seaway, the climate was moist and humid, reaching a steamy 120 degrees at times.

Thanks to more than 100 years of fossil collection, scientists know more about the Cretaceous dinosaurs from North American than they do from any other time or continent on Earth.

While G. monumentensis gulped down its greens and tried to avoid predatory tyrannosaurs down in Utah, closely related but different species of duck-billed dinosaurs were doing the same thing farther north, in places like Montana and Alberta, Canada.

The new Utah species is proving crucial for determining patterns of duck-billed dinosaur evolution and ecology during the Late Cretaceous of North America, Gates said. He added that “this calls for a re-evaluation of previous ideas about the evolution of duck-billed dinosaurs across the world."

The Gryposaurus fossils are being reassembled into a skeleton that will go on display at the new Utah Museum of Natural History in Salt Lake City.