Protoceratops is a well known ceratopsian from a land that is now known as Mongolia; but 84 to 72 million years ago, when Protoceratops roamed, it did not have a name. This dinosaur was about the size of a pig, growing to 1.5 to 2 meters long with a mass of 60 to 180 kg. It did not grow horns, but did have an enlarged bump on the nose which may have been used in shoving matches. The head shield varied in size and shape between individuals, and some had a more arched nose than others. These may represent differences between the sexes or different growth stages. Its tail had a raised ridge that likely sported some sort of display, perhaps a mane of hair-like quills or bristles.
Protoceratops probably roamed in herds through a dry, sandy desert landscape occasionally scoured by monsoon rains. It was one of the most abundant dinosaurs of its time and place. It lived alongside Velociraptor, Oviraptor, and the giant Tarbosaurus.
Protoceratops is one of the only dinosaurs for which we have direct evidence of how it fought. A remarkable pair of skeletons has been found of a Protoceratops locked in very mortal combat with a Velocirpator. The Protoceratops was crushing the arm of Velocirpator in its powerful jaws while Velocirpator had one of its raptorial claws embedded in the Protoceratops when they both died.