The Central Asiatic Expeditions, led by AMNH's Roy Chapman Andrews and Walter Granger, discovered some of the earliest, well-preserved dinosaur eggs in Mongolia during the 1920s. The oval-shaped eggs, about 20 cm long, were thought to belong to the most commonly found dinosaur at the Flaming Cliffs, Protoceratops. However, AMNH expeditions in the 1990s discovered identical eggs, one of which contained the embryo of an Oviraptor-like dinosaur, which altered our view of which dinosaur laid these eggs. Also, skeletons of Oviraptor were discovered squatting on top of clusters of eggs, with their arms folded back against their body, just like many living birds brood on their nests.