Chaoyangsauridae is a family of small, basal ceratopsians representing some of the earliest known members of the horned-dinosaur lineage, predating the more familiar frilled and horned giants of the Late Cretaceous by tens of millions of years. Living during the Late Jurassic, roughly 150 million years ago, chaoyangsaurids were modest in size, with skulls only a few centimeters long, poorly developed cheek bosses suggesting horns had not yet evolved in any prominent form, and a beaked snout adapted for cropping vegetation, alongside dozens of small cheek teeth suited to basic plant processing.
The family is known from the type genus Chaoyangsaurus and the closely related Xuanhuaceratops, both recovered from Late Jurassic rock in northeastern China, in the same general region that later produced the spectacularly preserved Jehol Biota. Chaoyangsauridae, together with the genus Psittacosaurus, is thought to represent an early branch close to the base of Ceratopsia, making these fossils important for understanding how the group's later hallmark features -- neck frills, facial horns, and enlarged body size -- evolved gradually from small, unadorned ancestors over the course of the Jurassic and Cretaceous.