Protoceratops andrewsi

It had a parrot-like beak and a bony neck frill but lacked the large brow and nasal horns of Triceratops. Some individuals developed small nasal bumps, and the frill changed noticeably as the animal matured.

Protoceratops was a relatively small, four-legged ceratopsian, commonly reconstructed at around 2 meters long. Its abundant fossils include juveniles and adults, making growth changes easier to study than in many dinosaurs.

The famous specimen preserves a Protoceratops locked in combat with Velociraptor mongoliensis. The Protoceratops clamps the predator's arm in its beak while the Velociraptor's sickle claw lies near its opponent's body.

Eggs found during the American Museum of Natural History expeditions were long attributed to Protoceratops because its skeletons were common nearby. Later discoveries showed that some of the best-known elongated eggs belonged instead to oviraptorid dinosaurs.