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 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.