Psittacosaurus was a small ceratopsian dinosaur from the Lower Cretaceous of what is now Asia, about 130 to 100 million years ago. It was more basal than other members of the Ceratopsia: it was bipedal, and had no horns or frill on its head. What made it a ceratopsian was its beak.
It is notable for being the most species-rich dinosaur genus, but there is no general agreement on these species. Nine to eleven species are named for fossils found in different regions of China, Mongolia and Russia, with a possible additional species from Thailand.
All species of Psittacosaurus were gazelle-sized bipedal herbivores with a high, powerful beak on the upper jaw. At least one species had long, quill-like structures on its tail and lower back, possibly with a display function. Psittacosaurs were early ceratopsians. They developed adaptations of their own, but they also shared features with later ceratopsians, such as Protoceratops and the elephant-sized Triceratops.