By Dan Whitcomb and Bob Mezan
LOS ANGELES (Reuters) - Fossils from the smallest dinosaur found in North America, a fleet-footed species only 28 inches long and weighing less than a rabbit, have gone on public display for the first time at a Los Angeles museum.
The bones were discovered in western Colorado in the late 1970s but only recently identified and named Fruitadens haagarorum by an international team of scientists.
The fossils represent the skulls, vertebrae, arms and legs of four individual dinosaurs and are housed at the Natural History Museum of Los Angeles County, which put them on display on Tuesday.
"We're really testing the limits of body size among dinosaurs," Luis Chiappe, director of the museum's Dinosaur Institute, told Reuters in an interview.
"Here's an animal that is estimated to have weighed about two pounds (0.91 kg) when it was full grown," he said. "So this is a really tiny dinosaur. It is the smallest known dinosaur from North America and one of the smallest dinosaurs ever."
Scientists say Fruitadens haagarorum lived about 150 million years ago, during the Late Jurassic period, probably darting between the legs of much larger dinosaurs such as Brachiosaurus, Allosaurus and Torvosaurus.
Unusual details in the skull, including a canine-like tooth at the front of the lower jaw and leaf-shaped teeth in the cheek region, along with the small body size, suggests it ate both plants and animals.
That would make Fruitadens haagarorum one of the latest surviving members of a group of dinosaurs called heterodontosaurids.
"We believe that that may be the secret for the very long life that this group of dinosaurs had," Chiappe said.
"They were in existence for about 100 million years and that's a very long time," he said. "Perhaps the fact that the later members of the group were generalists, they were not highly specialized in any particular niche, perhaps that gave them an edge and allowed them to live for so long as a group."
Chiappe said a species of dinosaur that lived in China and was thought to be closely related to the origin of birds may have been smaller than Fruitadens haagarorum but studies had not been conclusive.
(Editing by Jill Serjeant and John O'Callaghan)