oct 3, 2007
The Gryposaurus, discovered in southern Utah, had a distinct duck-like bill and a powerful, strengthened jaw.
The two-legged creature, described in the Zoological Journal of the Linnean Society, was more than 10m (30ft) long.
Analysis suggests that the dinosaur, which lived in the Cretaceous forests of North America about 65-80 million years ago, was a successful herbivore.
"When you combine the 800 teeth with the very large, strong jaw and beak you have a very formidable plant eater," said Dr Terry Gates of the Utah Museum of Natural History, one of the authors on the paper.
Gryposaurus monumentensis was found in Grand Staircase-Escalante National Monument in Utah.
The park is a favoured destination for palaeontologists, who have previously found other new species in the area including a Velociraptor-like carnivore called Hagryphus and a species of tyrannosaur.
"We also have several other types of herbivores, including three new species of horned dinosaur, some domed dinosaurs and armoured dinosaurs," Dr Gates told the BBC World Service's Science in Action programme.
"There were lots of animals living in the ecosystem."
At the time, North America was thought to be split by a shallow sea, dividing the continent into two.
The new species is believed to have lived on the western landmass on a strip of land running between the waterway and a range of mountains to the west.
The recently described specimen was probably fossilised when it was covered by river sediments that now make up a series of sandstones and mudstones known as the Kaiparowits Formation.
It was discovered in 2004 and analysis of its skull began in 2005.
The specimen is the fourth species of Gryposaurus known today. The other three species were discovered in rocks of a similar age in Alberta, Canada and Montana in the US.
"This is a brand new and extremely important window into the world of dinosaurs," said Dr Scott Sampson, also of the Utah Museum of Natural History.
Although the new specimen is similar to other members of the genus, there are crucial differences.
"The snout is very robust indeed - it is much larger and much stronger-looking than any other duck-billed dinosaur," said Dr Gates.
"In addition, the angle of the snout is more vertical, which initially leads to a hypothesis that it had a stronger bite."
Combined with 300 teeth inside its beak, with a further 500 in its jaw ready to grow as replacements, the creature could have sliced through large amounts of fibrous or woody plant material, the researchers believe.
However, Dr Gates admits that researchers are still uncertain about the specifics of the creature's diet.
"We just don't know what this dinosaur ate," he said.
But whilst the food preferences of the toothy Gryposaurus monumentensis remain a mystery, the diet of other creatures alive at the time do not.
"We have duck-billed dinosaur bones with both raptor and tyrannosaur teeth marks on them, so we know they were getting eaten by the predators."