of Chinese vertebrate paleontology. The holotype, IGCAGS V371, has been found in a layer of the Tuchengzi Formation that was in 1999 dated to the late Tithonian. It consists of a partial skeleton with skull. It contains the lower part and braincase of the skull, the lower jaws, seven neck vertebrae, the right shoulder blade and the right humerus. It represents an adult individual. The fossil was prepared by Ding Jinzhao and Wang Haijun. Description In 2010, Gregory S. Paul estimated the length of Chaoyangsaurus at one metre, the weight at six kilogrammes. The describing authors indicated some distinguishing traits. The boss on the jugal bone is only weakly developed and has a smooth surface. The convex quadratojugal bone overlaps the rear of the shaft of the quadrate bone. The quadrate lacks a wide side surface, not being expanded to the front. The rear lower edge of the quadrate is convex. The coronoid process of the lower jaw is low with a flat top. The planes of the side surface and the underside of the angular bone are separated by a ridge. The last five traits were considered autapomorphies. The skull is fourteen centimetres long. Per side, the appending lower cutting edge of the rostral bone, in life probably covered by horn, bears four crenulations. More to the rear, there are two conical premaxillary teeth, jutting out to below. The transversely flattened maxillary teeth number eight or nine, while there are eleven dentary teeth in the lower jaw for a maximal total of forty-four teeth for the head as a whole. The cheek teeth are imbricated and vertically rather long. Both inner and outer sides are covered by enamel. Phylogeny In 1999, Chaoyangosaurus was placed in the Ceratopsia, in a basal position. There were doubts whether it was outside or inside the Neoceratopia. In 2006, Zhao, et al defined a Chaoyangsauridae, as the most basal ceratopian clade. See also Timeline of ceratopsian research References Ceratopsians Ornithischian genera Tithonian genera Middle Jurassic dinosaurs of Asia Fossil taxa described in 1999 Taxa named by Xu Xing Taxa named by Zhao Xijin Paleontology in Liaoning