Field Guide
Evolutionary History
The Egg Thieves: A Case of Mistaken Identity

The first known oviraptorosaur skeleton, discovered in Mongolia in 1923, was found atop a clutch of dinosaur eggs thought to belong to the early horned dinosaur Protoceratops. Paleontologists therefore concluded that this theropod had died in the act of raiding a Protoceratops nest. This led to its being named Oviraptor philoceratops – literally, “egg thief who prefers horned dinosaurs.” It is from this dinosaur that the entire oviraptorosaur group takes its name.

In the 1990s, further expeditions to Mongolia turned up many more dinosaur fossils. However, paleontologists were shocked by what they found: a supposed “Protoceratops” egg with a baby oviraptorosaur inside! So the eggs that paleontologists originally thought belonged to horned dinosaurs actually belonged to oviraptorosaurs.

At the same time, a spectacular oviraptorosaur skeleton was discovered with its arms outstretched around a nest. The 22 eggs in this nest were the same kind as those that contained the baby oviraptorosaur...they were oviraptorosaur eggs! Since it’s not very likely that a parent would raid the nest of its own species, that adult appears to have died guarding its nest.

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