Cretaceous Parenting

By MICHAEL D. LEMONICK

Anyone who shuddered through Jurassic Park would never use the words motherly or nurturing to describe the movie's prehistoric villains -- especially not the vicious velociraptors and Tyrannosaurus rex that slashed their way across the screen. But those beasts may have had a softer side that moviegoers never saw.

In recent years, scientists have come to believe that on the evolutionary tree, dinosaurs are more closely linked to robins and sparrows than to lizards and crocodiles. Even the most ferocious dinosaurs may have been tender, caring parents, hovering like mother birds over their nests of hatchlings.

For many years the evidence of such motherly love applied only to peaceful, plant-eating dinosaurs. Now a dramatic discovery announced in the current Science suggests that the carnivores had a nesting instinct as well. Working with a U.S.-Mongolian team in the remote Gobi Desert, paleontologist Mark Norell of New York City's American Museum of Natural History found the nearly complete skeleton of a predatory-dinosaur embryo, the first ever discovered, fossilized just as it was about to hatch during the Cretaceous period, more than 70 million years ago. The embryo and its potato-size egg, found in a rocky nest along with at least eight other eggs, are from a kind of oviraptor, an ostrich-size cousin of both tyrannosaurs and velociraptors. And several aspects of the discovery make the parallels between dinosaurs and birds stronger than ever.

To start with, says Norell, the eggs he found are identical to eggs uncovered in 1923, also in the Gobi, by the famed fossil hunter Roy Chapman Andrews. Most of the bones in the area Andrews explored belonged to a vegetarian dinosaur called Protoceratops, so Andrews thought the eggs did too. Since a predator's remains were found lying on top of one clutch of eggs, scientists assumed that it had died in the act of eating them and named it Oviraptor, or egg stealer. But Norell's discovery makes it clear that the unfairly maligned "thief" was more likely a mother dinosaur incubating its own eggs.

Another clue to the monster's motherly instincts may come from two tiny skulls that Norell found in the nest. They belong to a different type of predatory dinosaur known as dromaeosaurs. While they could have been egg stealers themselves, they could also have been brought in by the mother oviraptor as food. Or they might have emerged from eggs sneaked into the nest by a mother dromaeosaur so her young could be raised by unsuspecting surrogate parents -- a strategy used by modern cuckoos.

Even if there had been no other fossils in the nest, the discovery of an embryonic oviraptor would have been important. Dinosaur embryos are rare -- fewer than a dozen kinds have ever been found. Juvenile animals often have features that vanish as the creatures grow, but which also exist in the embryos of their precursors or descendants (human fetuses, for example, start out with tiny tails). If researchers can find common traits in unhatched dinosaurs and birds, they will be able to establish stronger links between them.

Norell is planning a return next summer to the Gobi, where there are undoubtedly more surprises awaiting. Jurassic Park 2 may have to take into account the mounting evidence that Tyrannosaurus and its kin resembled nesting robins -- albeit big robins with sharp teeth and really bad tempers.

With reporting by Andrea Dorfman/New York