''Yinlong'' (, meaning "hidden dragon") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of basal

ceratopsia Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurass ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the Late Jurassic Period of

central Asia Central Asia, also known as Middle Asia, is a region of Asia that stretches from the Caspian Sea in the west to western China and Mongolia in the east, and from Afghanistan and Iran in the south to Russia in the north. It includes the fo ...

. It was a small, primarily bipedal

herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

Discovery and species

A coalition of

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

and Chinese

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

s, including Xu Xing,

Catherine Forster Catherine Ann Forster is an American paleontologist, taxonomist and expert in ornithopod evolution and ''Triceratops ''Triceratops'' ( ; ) is a genus of herbivorous chasmosaurine ceratopsid dinosaur that first appeared during the late Maa ...

Jim Clark James Clark Jr. OBE (4 March 1936 – 7 April 1968) was a British Formula One racing driver from Scotland, who won two World Championships, in 1963 and 1965. A versatile driver, he competed in sports cars, touring cars and in the Indianap ...

, and Mo Jinyou, described and named ''Yinlong'' in 2006. The generic name is derived from the

Mandarin Chinese Mandarin (; ) is a group of Chinese (Sinitic) dialects that are natively spoken across most of northern and southwestern China. The group includes the Beijing dialect, the basis of the phonology of Standard Chinese, the official language ...

words 隱 (''yǐn'': "hidden") and 龍 (''lóng'': "dragon"), a reference to the movie ''

Crouching Tiger, Hidden Dragon ''Crouching Tiger, Hidden Dragon'' is a 2000 wuxia film directed by Ang Lee and written for the screen by Wang Hui-ling, James Schamus, and Tsai Kuo-jung . The film features a cast of actors of Chinese ethnicity, including Chow Yun-fat, ...

'', large portions of which were filmed in the western Chinese province of

Xinjiang Xinjiang, SASM/GNC: ''Xinjang''; zh, c=, p=Xīnjiāng; formerly romanized as Sinkiang (, ), officially the Xinjiang Uygur Autonomous Region (XUAR), is an autonomous region of the People's Republic of China (PRC), located in the northwes ...

, near the locality where this animal's

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

remains were discovered. ''Long'' is the word most often used in the Chinese media when referring to dinosaurs. The

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

was named after the American vertebrate paleontologist William Randall Downs III, a frequent participant in paleontological expeditions to China who died the year before ''Yinlong'' was discovered.Xu, X., Forster, C.A., Clark, J.M., and Mo, J. (2006).
A basal ceratopsian with transitional features from the Late Jurassic of northwestern China
" ''Proceedings of the Royal Society B: Biological Sciences'', 273(1598): 2135-2140. The known fossil material of ''Yinlong'' consists of many skeletons and skulls. The first specimen discovered was a single exceptionally well-preserved skeleton, complete with

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

, of a nearly adult animal, found in 2004 in the Middle-

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

strata of the Shishugou Formation located in Xinjiang Province, China. ''Yinlong'' was discovered in an upper section of this formation which dates to the Oxfordian stage of the Late Jurassic, or 161.2 to 155.7 million years ago.Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'
Winter 2010 Appendix.
/ref> Most other described ceratopsians are known from the later Cretaceous Period.

Description

''Yinlong'' was a relatively small dinosaur, reaching in length and in body mass. Despite a virtually frill-less and totally hornless skull, ''Yinlong'' is a ceratopsian. Its skull is deep and wide and relatively large compared to most ornithischians, but also proportionately smaller than most other ceratopsians. Long robust hindlimbs and shorter slender forelimbs with three-fingered hands suggests a bipedal lifestyle like many small ornithopods.

Classification

A small rostral bone on the end of the upper jaw clearly identifies ''Yinlong'' as a ceratopsian, although the skull displays several features, especially the ornamentation of the

squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...

bone of the skull roof, which were previously thought to be unique to pachycephalosaurians. The presence of these features in ''Yinlong'' indicates these as actual

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ha ...

(unique features) of the larger group Marginocephalia, which contains both the pachycephalosaurs and the ceratopsians, although these features have been lost in all known ceratopsians more

derived Derive may refer to: *Derive (computer algebra system), a commercial system made by Texas Instruments * ''Dérive'' (magazine), an Austrian science magazine on urbanism *Dérive, a psychogeographical concept See also * *Derivation (disambiguation ...

than ''Yinlong''. The addition of these characters further strengthens the support for Marginocephalia. ''Yinlong'' also preserves skull features reminiscent of the family

Heterodontosauridae Heterodontosauridae is a family of ornithischian dinosaurs that were likely among the most basal (primitive) members of the group. Their phylogenetic placement is uncertain but they are most commonly found to be primitive, outside of the group ...

, providing support for the

hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...

that heterodontosaurids are closely related to marginocephaliansZhao X., Cheng Z., & Xu X. 1999. "The earliest ceratopsian from the Tuchengzi Formation of Liaoning, China." ''Journal of Vertebrate Paleontology'' 19(4): 681-691.Cooper, M.R. 1985. "A revision of the ornithischian dinosaur ''Kangnasaurus coetzeei'' Haughton, with a classification of the Ornithischia." ''Annals of the South African Museum'' 95: 281-317.You H., Xu X. & Wang X. 2003. "A new genus of Psittacosauridae (Dinosauria: Ornithopoda) and the origin and early evolution of marginocephalian dinosaurs." ''Acta Geologica Sinica (English edition)'' 77: 15–20. The group containing Marginocephalia and Heterodontosauridae has been named Heterodontosauriformes. However, this hypothesis was not supported by a subsequent analysis of basal ornithischians that was carried out as part of a study on the postcranial anatomy of ''Yinlong'', which resolved the below phylogeny of Ceratopsia. Guanlong and Yinlong

Diet

''Yinlong'' was discovered with seven gastroliths preserved in the abdominal cavity. Gastroliths, stones stored in the

digestive tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...

and used to grind plant material, are also found in other ceratopsians such as '' Psittacosaurus'', and are also widely distributed in most other dinosaur groups, including

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

References

External links

GW News Center
featuring a link to the original paper, pictures, and a press release on the discovery of ''Yinlong'' (site operated by

George Washington University , mottoeng = "God is Our Trust" , established = , type = Private federally chartered research university , academic_affiliations = , endowment = $2.8 billion (2022) , presi ...

) {{Taxonbar, from=Q132877 Ceratopsians Ornithischian genera Oxfordian genera Late Jurassic dinosaurs of Asia Jurassic China Fossils of China Paleontology in Xinjiang Fossil taxa described in 2006 Taxa named by Catherine Forster