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

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

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 Jurassic. ...

n dinosaur from the Late Jurassic Period of central Asia. 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 mouthpart ...

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 paleontologists, including Xu Xing, Catherine Forster,

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 Indianapol ...

, and

Mo Jinyou Mo or MO may refer to: Arts and entertainment Fictional characters * Mo, a girl in the ''Horrible Histories'' TV series * Mo, also known as Mortimer, in the novel ''Inkheart'' by Cornelia Funke * Mo, in the webcomic '' Jesus and Mo'' * Mo, the ...

, described and named ''Yinlong'' in 2006. The generic name is derived from the Mandarin Chinese 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 people, Chinese ethnicity, including Ch ...

'', large portions of which were filmed in the western Chinese province of Xinjiang, near the locality where this animal's fossil remains were discovered. ''Long'' is the word most often used in the Chinese media when referring to dinosaurs. The species was named after the American

vertebrate paleontologist Vertebrate paleontology is the subfield of paleontology that seeks to discover, through the study of fossilized remains, the behavior, reproduction and appearance of extinct animals with vertebrae or a notochord. It also tries to connect, by u ...

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

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- Late Jurassic 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 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 have ...

(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 (disambiguatio ...

than ''Yinlong''. The addition of these characters further strengthens the support for Marginocephalia. ''Yinlong'' also preserves skull features reminiscent of the family Heterodontosauridae, providing support for the hypothesis 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 Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek ...

. 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 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 birds.

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) {{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