New dinosaur embryo rewrites history.

In 1923, at the Flaming Cliffs in Mongolia's Gobi desert, scientists from the American Museum of Natural History identified dinosaur eggs for the first time. They classified the eggs as belonging to Protoceratops, a small, plant-eating creature abundant in the area. Now, new evidence suggests that those investigators unknowingly mislabeled their find, researchers assert.

A member of the dinosaur family Oviraptoridae laid those eggs, report Mark A. Norell, also of the American Museum of Natural History in New York City, and his colleagues in the Nov. 4 SCIENCE. They are the first Western paleontologists allowed to search for fossils in Mongolia since 1930.

Norell and his colleagues compared their find -- a 70- to 80-million-year-old shell containing the nearly complete skeleton of an oviraptorid embryo -- to the empty eggshells discovered by the earlier scientists. Norell's team found the embryo last year several hundred kilometers from the Flaming Cliffs.

Researchers have uncovered only six or seven dinosaur embryos. This find marks the first discovery of a meat-eating dinosaur embryo, the team asserts.

The discovery "sort of cleared up this mystery of what the dinosaur eggs from the Flaming Cliffs were, which in paleontological circles has always been a pretty big thing," says Norell.

An oviraptorid dinosaur resembled a small ostrich with a tail, grew to about 6 feet in length, and sported a hornlike bump on the end of its beak. Identifying the embryo proved easy. The animal died right before it would have hatched and "looks like a little adult inside the egg," Norell says. Also, "the skulls of oviraptorids are so unusual that they can't be confused with anything [else]," he explains.

The new embryo clears up another mistake made by the earlier investigators. The scientists in 1923 gave the name Oviraptor philoceratops, or egg eater, to a dinosaur they found lying on top of a nest of what they thought were Protoceratop eggs, Norell says. However, the Oviraptor "was probably the parent of those eggs and was either incubating or guarding that nest," he speculates.

Scientists know little about how dinosaurs handled their eggs, but finding a parent so close to its nest suggests they didn't just leave them to hatch, he asserts. The eggs were arranged in a circular pattern, he adds. "This is the best association [ever found] of any adult dinosaur with a nest," says Paul C. Sereno of the University of Chicago.

In the nest with the oviraptorid embryo lay skulls of juvenile dromaeosaurid dinosaurs, which the oviraptorid parents may have brought to the nest to feed on, the researchers report. Or the dromaeosaurids may have gone to the nest in search of dinner, they suggest. This is the first time scientists have discovered juvenile dromaeosaurid skulls.

The study provides a host of valuable new evidence about dinosaurs, says Sereno. "It was a really great paper."