The skull of a newly-discovered dinosaur species in Utah, Gryposaurus monumentensis, looked pretty amazing from the outside. Scientists call this different-looking dino a duck-billed dinosaur.

The strong bill was useful for ripping leaves from plants. But what’s inside the skull is even more amazing: for starters, some 300 teeth for grinding up the leaves it ate.

This dinosaur also had plenty of extra teeth ready to drop into place as some wore out from all that chewing.  “There are slots in their jaws for 40 to 50 rows of teeth, depending on their age,” says paleontologist Terry Gates of the Utah Museum of Natural History, one member of the research team studying the fossil skull.  “Each slot has four or five replacement teeth. So when you do the math—two hundred times four jaws—you’ll see that there are a total of 800 teeth.” The big dinosaur must have eaten a lot of leaves to fuel its huge body and wear out so many teeth.

A researcher found the skull at the Grand Staircase-Escalante National Monument in a remote part of Utah, where fossils from many species of dinosaurs have been discovered.

Additional bones turned up about three miles away, enabling paleontologists to figure out that this giant was at least 30 feet (9.14 meters) long. “The humerus, or upper arm bone, is longer than my leg—it comes up to my hip,” says Gates.

Gryposaurus monumentensis roamed this region looking for food during the Late Cretaceous Period, which was 75 million years ago. “We know the area was wet, humid, and swampy,” says Gates. “There were lots of plants, but we don’t know yet what they ate.”

Paleontologists are surprised that the duck-billed dinosaurs from Utah are different than duck-billed dinosaurs that lived in Alberta, Canada, in what is now Dinosaur Provincial Park.

“Why aren’t they the same?” wonders Gates. He says such a large dinosaur should have been able to travel long distances. “Maybe they ate special food and didn’t want to leave it. Or was there a river or mountain system blocking their way?”

“Paleontologists don’t just dig up fossils, name new species, and throw fossils in a museum,” he explains. “We use them to look at the evolution of life at that time in many parts of the world.”

Gates says new research will focus on nearby Colorado and Wyoming looking for clues. What they learn about Gryposaurus monumentensis will help our understanding of dinosaur evolution.