Fossil Indicates Dinosaurs Nested on Eggs : Science: Discoverers say the find shows a behavioral link to birds.
In the sands of Mongolia’s Gobi Desert, scientists have discovered a unique fossil of a carnivorous dinosaur nesting on its eggs like a brooding bird, revealing for the first time how Earth’s most fearsome parents may have tenderly cared for their young.
The 80-million-year-old fossil is graphic testimony that the nesting behavior so common among birds today actually originated long before modern feathers and wings, reinforcing the intimate evolutionary link between birds and the long-extinct dinosaurs. It proves they share complex behavior, several dinosaur experts said, in addition to important anatomical features.
Indeed, the sandstone fossil of a 9-foot-long, beaked carnivorous dinosaur called an oviraptor, preserved with a nest and a brood of unhatched young, is the sole direct evidence of any dinosaur behavior, experts said.
Until now, scientist could only make educated guesses about parental care among dinosaurs, by studying fossil nests and juvenile dinosaurs. The fossil of the oviraptor on its eggs offers the first concrete proof that dinosaurs actively protected and cared for their young, said researchers from the American Museum of Natural History and the Mongolian Academy of Sciences who made their find public Wednesday.
“What makes this specimen so spectacular is that, while there is a lot said and a lot written about dinosaur behavior, there is very little real evidence,” said Mark A. Norell, associate curator of vertebrate paleontology at the American museum, who led the team that discovered the bones. “This is about the only piece of hard evidence we have.”
David B. Weishampel, a dinosaur expert at Johns Hopkins University, called the discovery “astonishing and incontrovertible evidence.” Jack Horner, curator of paleontology at the Museum of the Rockies in Bozeman, Mont., said it is “the strongest evidence of some kind of parental attention.” Jacques Gauthier, curator of reptiles at the California Academy of Science, said the find “opens all kinds of possibilities.”
Norell and his colleagues, like many dinosaur experts, are convinced that all modern birds are direct descendants of a group of meat-eating, bipedal dinosaurs called theropods, a group that includes the oviraptor, the rapacious velociraptors made famous in the novel “Jurassic Park” and the tyrannosaurus rex--the largest carnivore to walk the planet. Many ornithologists do not subscribe to that theory. Several said the new fossil is unconvincing, circumstantial evidence.
Alan Feducci, an authority at the University of North Carolina on bird evolution, said the fossil “makes no sense” and challenged the way its discoverers have linked their find to the development of birds.
“I have no faith in their conclusions whatsoever,” he said. “It is a stretch of credulity. There are numerous animals preserved in bizarre poses. Maybe it was laying an egg instead of brooding the eggs. That would make more sense.”
As presented by the American Museum of Natural History on Wednesday, however, the fossilized rock captures a moment more than 80 million years ago when a bipedal, meat-eating dinosaur roughly the size of an ostrich, with a whip tail and six-inch talons, warmed its clutch of about 15 large eggs. The eggs, shaped like baking potatoes, are neatly arranged in a circle.
Overtaken perhaps by a sudden sandstorm, the dinosaur was preserved as it sat on the eggs. Its arms are turned back to encircle the nest and its legs are tucked tightly against its body, identical to the nesting posture of birds, such as chickens and pigeons, living today.
It was the sight of a few daggerlike talons protruding from the earth at Ukhaa Tolgod, Mongolia, that first drew the scientists’ attention. They excavated only enough of the skeleton to identify the specimen and discover the nest. Then they bundled the fossil in a 400-pound plaster cast for shipment to New York. It was not until the fossil was examined at the museum in New York that the researchers realized the importance of what they had found.
Scientists do not know why the creature was sitting on the eggs. Perhaps, Gauthier suggested, it was incubating the eggs to warm them as birds do, shading them, or simply protecting them. The researchers do not know when the brooding behavior first developed, but suggested it was extremely ancient even among dinosaurs.
“Because oviraptors are so closely related to birds, our best bet is that it was present in the common ancestor of birds and oviraptors, so this behavior predates the origin of modern birds,” Norell said.
