Chaoyangsauridae is a family of dinosaurs. They are the earliest known marginocephalian dinosaurs to appear on the planet, about 148 million years ago, in the Late Jurassic period. Members of this group had sharp beaks for snipping off leaves to eat, and a very small frill. There are disagreements that the chaoyangsaurids were part of the pachycephalosaurian group, ceratopsian group, or a different ancestral group. Two dinosaur genera, Chaoyangsaurus and Xuanhuaceratops, are included in Chaoyangsauridae. Both animals are more primitive (or basal) than Psittacosaurus, an early ceratopsian.