"All therizinosaurs other than the new animal, Falcarius, have a lower jaw which is downturned at the front,” said Scott Sampson, a member of the research team and chief curator at the Utah Museum of Natural History.
"They also tend to have a shelf of bone on the lower jaw that causes the teeth to be inset from the side of the jaw. These features are absent in Falcarius, suggesting that it represents a primitive form."
The first dinosaurs were all light and fleet-footed carnivores before some groups evolved into plant eaters.
Falcarius shows signs of the dietary shift, as the dinosaur possessed an expanded gut capable of fermenting plant material. Its legs supported a semi-bulky body, and its teeth could either have shredded leaves or cut into extremely soft meat, such as carrion.
Falcarius might have been an omnivore or a vegetarian, since flowering plants evolved and spread approximately 125 million years ago during the Early Cretaceous period in which it lived.
"This could be coincidence, but may also be related," Sampson told Discovery News. "That is, the evolution of flowering plants resulted in a widespread, varied and easily digestible food source that may have allowed for new kinds of plant-eating animals."
No feathers were found with the fossils, but Sampson said, "a number of its close relatives found in China had feathers (preserved by unusual lake sediments) so the presumption is this animal too was feathered."
The dino stood 4.5 feet tall and had sharp, curved 4-inch-long claws. Its height may have allowed it to reach up and swipe at leafy plants, or it could have used its claws to dig for roots.
