[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 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".

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 also be considered a nomen nudum.

[8] The holotype, IGCAGS V371, has been found in a layer of the Tuchengzi Formation that was in 1999 dated to the late Tithonian.

Per side, the appending lower cutting edge of the rostral bone, in life probably covered by horn, bears four crenulations.