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.”
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.
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