Protoceratops is the oldest of the horned dinosaur group, the suborder Ceratopsia in the order Ornithischia. Known from a great many skeletons collected in the Gobi Desert of Mongolia from late Cretaceous strata, about 90 million years old, it is one of the few dinosaurs whose very young stages are known. (The first dinosaur eggs to be discovered, in 1922, were once also attributed to Protoceratops but are now identified as those of Oviraptor.) Protoceratops, a herbivore, was about 2 m (6.5 ft) long and weighed 140 kg (300 lb) or more. It had a large turtle-beaked head, almost as long as the trunk of the body, and the flattened parietal and squamosal bones at the rear of the skull were flared out to form a crest, or frill. Unlike its descendants, it had no horns. Protoceratops has been found only in Asia, but all of its descendants are known only from North America.

Bibliography: Dixon, Dougal, Dougal Dixon's Dinosaurs (1994); Glut, Donald F., Dinosaurs: The Encyclopedia (1995); Hatcher, John B., The Ceratopsia (1980).