Yinlong (, meaning "hidden dragon") is a genus of basal dinosaur from the Late Jurassic Period of China. By far the earliest known ceratopsian, it was a small, primarily herbivore.
Discovery and species
A coalition of
United States and Chinese
, including Xu Xing, Catherine Forster, Jim Clark, and
Mo Jinyou, 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, 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 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.[Holtz, Thomas R. Jr. (2011) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages, Winter 2010 Appendix.] 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.
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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 synapomorphy (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 Synapomorphy than Yinlong.[Zhao 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.
Paleobiology
Diet
Yinlong was discovered with seven 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 .
Growth
In 2024, bone histology based on specimens of various ontogenetic stage (1 early juvenile, 2 late juveniles, 4 subadults and 3 adults) suggested that Yinlong reached sexual maturity at 6 years old, much younger than the age of sexual maturity for Psittacosaurus but older than that for Ceratopsidae. The study also found evidence of growth rates higher than those of extant squamates and crocodiles but lower than those of large-sized dinosaurs and extant mammals and birds.
See also
-
Timeline of ceratopsian research
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)
