Chaoyangsaurus

Phylogeny: Dinosauria > Ornithischia > Genasauria > Neornithischia > Cerapoda > Marginocephalia > Ceratopsia > Chaoyangsauridae

Overview: Fossils of this small herbivore have been known to science since the mid-1970’s, but the find would go without a formal description for a couple decades. The bones would be mentioned in a few publications, informally referred to as “Chaoyoungosaurus”, but it wouldn’t be until 1999 that an official publication was released along with its current name – Chaoyangsaurus. Said name refers to the county of Chaoyang, in the Liaoning Province of northeastern China, where the fossils were first discovered. These fossils consisted of portions of the skull and jaws, neck vertebrae, and some bones from its forelimbs. Fairly early on, Chaoyangsaurus was recognized as ceratopsian. Its status as such was significant, as it was one of the first ceratopsians discovered within rocks dated to the Jurassic Period. Most of the well known ceratopsians originated from the Cretaceous.

Chaoyangsaurus would go on to become the namesake of its own family, the Chaoyangsauridae. It is to this family that many of the most basal and earliest known ceratopsids belonged, including the genus Yinlong. The most derived of the ceratopsians, such as Triceratops or Pachyrhinosaurus, grew to be quite enormous, were quadrupedal, and often had extravagant cranial ornamentation like large bony frills, spikes or horns. Chaoyangsaurus shows us that such animals evolved from mostly small, bipedal ancestors without horns or spiked frills. This genus did possess the very beginnings of a frill, taking on the form of a small ridge of bone at the back of the skull. All ceratopsians, both basal and derived, possessed sharp, parrot-like beaks. Lacking horns or armor, Chaoyangsaurus likely used its beak as its main defense. Said beak was also useful for snipping stems and twigs.