Utah scientists have discovered one near the Arizona border that's even more threatening.
"It really is like the Arnold Schwarzenegger of dinosaurs - it's all pumped up," said Scott Sampson, curator of the Utah Museum of Natural History.
The newly named Gryposaurus monumentensis, or hook-beaked lizard from the monument, was discovered in the Grand Staircase-Escalante National Monument in 2002 by a Pennsylvania furniture maker who volunteered to work at the site. Details about the dinosaur, including its name were published in the Oct. 3 edition of Zoological Journal of the Linnean Society.
At least 30 feet long and 10 feet tall with a robust jaw and thick bones, the 75-million-year old animal was like a duck-billed dinosaur on steroids, said paleontologist Terry Gates.
"It's basically the Cretaceous version of a weed-whacker," he said. "You have a very formidable herbivore."
Although paleontologists said Wednesday that the dinosaur could eat just about any plant it wanted, scientists still aren't sure what it dined on.
Southern Utah is a rocky desert with few trees today, but it was a much different place 75 million years ago.
At the time, North America was divided down the middle by an ocean and southern Utah looked similar to Louisiana, Gates said.
"It's very humid and wet, with lots of ponds and lots of rivers and creeks flowing through it. It was very lush," he said.
The area was a haven for dinosaurs. Gryposaurus monumentensis is one of several new species found in Grand Staircase in recent years.
"I knew this thing would be an important piece of a much larger puzzle we're trying to solve. Grand Staircase is one of the last untapped treasure troves," Sampson said.
The discovery of new species, including Gryposaurus monumentensis, will help scientists understand more about what the earth was like millions of years ago, he said.
Sampson said duck-billed dinosaurs can be found throughout the northwestern part of North America, just like many other animals such as deer. But he said scientists don't find different species of deer close together as they have with the duck-billed dinosaur. The new version of the dinosaur has a smaller skull that allowed it to apply more force to what it was eating.
"By shortening the skull, you can get more power per bite. The shrinking of the skull and the robustness of the jaw and snout all lead me to think this guy was made to eat," Gates said.
However, the duck-billed dinosaur's teeth and size would not have been much of a defense against area predators such as the tyrannosaur. Scientists also aren't sure if the new dinosaur was a loner or traveled in herds for protection because so few skeletal remains have been found.
It's one of several questions scientists are hoping to answer, along with how and why different species of the duck-billed dinosaur developed.
"To find an animal so closely related to something up in Montana and so close by, we would've expected it to be same type of Gryposaurus. The fact it isn't raises some eyebrows," he said.
"This animal, it answered a number of questions. It also poses a number of others."