The first known embryo of a meat-eating dinosaur, found in the Gobi Desert still in its fossilized egg, gives further evidence to support the theory that has emerged in recent years that dinosaurs -- as big and clumsy as they may have been -- perhaps sat on nests and brooded their young like mother hens, scientists reported Friday.


The discovery of the 80 million-year-old embryo, curled up with its head between its knees, is likely to force a sharp change in the image of this dinosaur, researchers from the American Museum of Natural History reported in the journal Science.


Although the dinosaur, called Oviraptor, has always been considered a ruthless predator that raided the nests and killed the young of other dinosaur species, the new evidence suggests that it was, in addition, a nurturing parent.


The team of researchers also found two skulls of newborn dinosaurs, which are among the rarest fossils in the world. Both the Oviraptor embryo and the Velociraptor skulls have many birdlike characteristics, providing strong new support for the growing consensus among scientists that birds evolved from dinosaurs.


"It's really great to see this fossilized behavior," said Jacques Gauthier, curator of reptiles at the California Academy of Sciences in San Francisco. "It complements what we already know from the rest of anatomy. Birds are just barely modified dinosaurs, even down to their behavior."


The find also shows how one scientist's mistake can persist through subsequent generations of researchers.


The first example of Oviraptor was discovered in 1923 at a site called Flaming Cliffs, in the Gobi, lying sprawled over a nest of eggs, the apparent victim of a sudden sandstorm. The eggs were common in the area, and a plant-eating dinosaur called Protoceratops was also the most common species, so researchers believed that the eggs were also Protoceratops.


The researchers assumed the dinosaur, a 2-meter-tall, ostrich-like beast with long limbs and a vicious beak, was stealing eggs. They named it Oviraptor, or "egg seizer."


The discovery that the eggs were not Protoceratops but Oviraptor suggests that the original researchers jumped to a too-hasty conclusion. Since it turns out that adults and eggs were of the same species, Norrell said, the discovery was not of a predator laying waste to the nests of a different species but of a parent that probably died protecting its eggs from a desert storm, he said.


Another indication that Oviraptor was a nurturing parent was that the 15-centimeter-long eggs were not randomly jumbled in the nest, the way reptile eggs usually are, but were geometrically aligned in either concentric circles or in a precise spiral, with their narrow ends pointed toward the center of the nest. Many modern birds move their eggs around in the same way.


"This is another indication that the types of behaviors we see in living birds have very, very deep roots within dinosaurian history," Norrell said.