Late Cretaceous dinosaur fossils were helicoptered out of The Grand

Staircase-Escalante National Monument in southern Utah this week. The bones transported from the site represent a Gryposaurus monumentensis, an

ankylosaur, a pterosaur, dinosaur-era turtles and a crocodile, along with other species that lived in Utah 75 million years ago.

“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


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


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