Chaoyangsaurus ("Chaoyang lizard") is a marginocephalian dinosaur from the Late Jurassic of China. It has been dated to between 150.8 and 145.5 million years ago.[1] Chaoyangsaurus belonged to the Ceratopsia (Greek for "horned faces"). Chaoyangsaurus, like all ceratopsians, was primarily a herbivore.[2][3]
In 1976, the remains of Chaoyangsaurus were found by Cheng Zhengwu at Ershijiazi, in the Chaoyang area of Liaoning Province in northeastern China. The fossil was added to a travelling exhibition.
Unlike many other dinosaurs, Chaoyangsaurus had been discussed in a number of sources before its official publication. As a result of this, several different spellings of its name have come and gone as invalid nomina nuda ("naked names", names with no formal description behind them). The first name to see print was Chaoyoungosaurus, which appeared in the guidebook to a Japanese museum exhibit, and was the result of an incorrect transliteration from the Chinese into the Latin alphabet. Zhao Xijin in 1983 also used this spelling when he first discussed the species,[4] again lacking a description so it is technically a nomen nudum. Two years later, Zhao again used this early spelling when he assigned a type specimen and species name, Chaoyoungosaurus liaosiensis.[5]
According to Dong Zhiming in 1992, the name Chaoyoungosaurus had been officially described in a separate paper by Zhao and Cheng in 1983, but no cite for this paper was given, and later Cheng and Zhao themselves did not treat this name as valid, perhaps because the paper had not actually been published. Dong, in his 1992 book on Chinese dinosaur faunae, also emended the name to the "correct" spelling of Chaoyangosaurus (note the extra letter "o").[6] However, since this renaming was not accompanied by a formal description of the dinosaur, Chaoyangosaurus must be considered a nomen nudum also.
It was not until 1999 that the dinosaur finally received an official name. Paul Sereno in 1999 used the name Chaoyangsaurus in an overview of dinosaurian evolution.[7] Once again, that name was a nomen nudum. However, in December of that year, Cheng, Zhao, and Xu Xing published an official description using the name Chaoyangsaurus youngi, and as the first name for this genus that is not a nomen nudum, it has official priority over all other spellings that have been used. The generic name refers to Chaoyang. The specific name honours the Chinese paleontologist Yang Zhongjian ("C. C. Young") as the founder of Chinese vertebrate paleontology.[8]
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.[8]