"It's one of the last groups of dinosaurs that we would expect to be that big," said Mark Norell, curator of paleontology at the American Museum of Natural History in New York City.

But Philip Currie, a paleontologist at the University of Alberta, said the size of the Gigantoraptor would be a natural step in the evolutionary process of the oviraptors.

"Almost every group that has evolved has tended to evolve giant forms," Currie said.

Animals tend to become bigger with evolution because larger creatures have an easier time getting food, impressing potential mates and avoiding predators.

But size has disadvantages, too. Bigger animals need more food and territory. They have fewer offspring and reproduce less frequently than smaller animals do. That means they are particularly vulnerable when environmental conditions change, as they abruptly did about 65 million years ago. Just a few million years after Gigantoraptor evolved, it and every other dinosaur species on Earth became extinct.

On Wednesday, reporters were given a look at the Gigantoraptor's remains ЎЄ two yellowing, rough-edged leg bones both a little over 3.2 feet long and believed to be those of a young adult.

It has not been determined whether the Gigantoraptor was a herbivore, which have small heads and long necks, or a carnivore, which have sharp claws. The dinosaur has both, Xu said.

Xu and his team, which discovered three other specimens in the fossil-rich Erlian Basin, were being interviewed by Japanese media in 2005 when they discovered the Gigantoraptor remains.

They had chosen a random site to illustrate how one of the previous fossils had been discovered and hit upon a bone while on camera, Xu said. The team originally thought that it belonged to a tyrannosaur because of its size, but realized upon examination that it was an oviraptor.

"It was an unexpected finding," Xu said.

Editor:Chen Ge