''Chaoyangsaurus'' ("
Chaoyang lizard") is a
marginocephalian
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
from the Late
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
of
China
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...
. It has been dated to between 150.8 and 145.5 million years ago.
''Chaoyangsaurus'' belonged to the
Ceratopsia
Ceratopsia or Ceratopia ( or ; Ancient Greek, Greek: "horned faces") is a group of herbivore, herbivorous, beaked dinosaurs that thrived in what are now North America, Asia and Europe, during the Cretaceous Period (geology), Period, although ance ...
(
Greek
Greek may refer to:
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group
*Greek language, a branch of the Indo-European language family
**Proto-Greek language, the assumed last common ancestor of all kno ...
for "horned faces"). ''Chaoyangsaurus'', like all ceratopsians, was primarily a
herbivore
A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat ...
.
Discovery and naming

In 1976, the remains of ''Chaoyangsaurus'' were found by Cheng Zhengwu at Ershijiazi, in the
Chaoyang area of
Liaoning Province
)
, image_skyline =
, image_alt =
, image_caption = Clockwise: Mukden Palace in Shenyang, Xinghai Square in Dalian, Dalian coast, Yalu River at Dandong
, image_map = Liaoning in China (+all claims hatched).svg
, ...
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
Nomen may refer to:
*Nomen gentilicium, the middle part of Ancient Roman names
** ''Nomen est omen'', a Latin quote about nominative determinism
*Nomen (ancient Egypt), the personal name of Ancient Egyptian pharaohs
*Jaume Nomen (born 1960), Catal ...
'' ("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
Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
alphabet
An alphabet is a standard set of letter (alphabet), letters written to represent particular sounds in a spoken language. Specifically, letters largely correspond to phonemes as the smallest sound segments that can distinguish one word from a ...
.
Zhao Xijin in 1983 also used this spelling when he first discussed the species, 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".
According to
Dong Zhiming
Dong Zhiming (Chinese language, Chinese: 董枝明, Pinyin: ''Dǒng Zhimíng''; January 1937 – 20 October 2024) was a Chinese vertebrate paleontologist formerly employed at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) ...
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"). However, since this renaming was not accompanied by a formal description of the dinosaur, "Chaoyangosaurus" must also be considered a ''nomen nudum''.
It was not until 1999 that the dinosaur finally received an official name.
Paul Sereno
Paul Callistus Sereno (born October 11, 1957) is a professor of paleontology at the University of Chicago who has discovered several new dinosaur species on several continents, including at sites in Inner Mongolia, Argentina, Morocco and Niger. ...
in 1999 used the name "Chaoyangsaurus" in an overview of dinosaurian evolution. 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 Specific name may refer to:
* in Database management systems, a system-assigned name that is unique within a particular database
In taxonomy, either of these two meanings, each with its own set of rules:
* Specific name (botany), the two-part (bino ...
honours the Chinese paleontologist
Yang Zhongjian
Yang Zhongjian, also Yang Chung-chien (; 1 June 1897 – 15 January 1979), courtesy name Keqiang (), also known as C.C. (Chung Chien) Young, was a Chinese paleontologist and zoologist. He was one of China's foremost vertebrate paleontologists. ...
("C. C. Young") as the founder of Chinese vertebrate paleontology.
The
holotype
A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
, IGCAGS V371, has been found in a layer of the
Tuchengzi Formation that was in 1999 dated to the late
Tithonian
In the geological timescale, the Tithonian is the latest age (geology), age of the Late Jurassic Epoch and the uppermost stage (stratigraphy), stage of the Upper Jurassic Series. It spans the time between 149.2 ±0.7 annum, Ma and 143.1 ±0.6 (mi ...
. 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
Gregory Scott Paul (born December 24, 1954) is an American freelance researcher, author and illustrator who works in paleontology. He is best known for his work and research on theropoda, theropod dinosaurs and his detailed illustrations, both l ...
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
In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
.
See also
*
Timeline of ceratopsian research
References
{{Taxonbar, from=Q133276
Chaoyangsauridae
Dinosaur genera
Tithonian dinosaurs
Taxa named by Zhao Xijin
Taxa named by Xu Xing
Fossil taxa described in 1999
Dinosaurs of China