Yinlong, meaning “hidden dragon,” is a genus of ceratopsian dinosaur from the Late Jurassic Period of what is now central Asia. A team of American and Chinese paleontologists — Xu Xing, Catherine Forster, Jim Clark, and Mo Jinyou — described and named Yinlong in 2006. Its name is in fact a reference to the movie “˜Crouching Tiger, Hidden Dragon,’ large portions of which were filmed in Xinjiang, near the area where the fossil remains of Yinlong were discovered.

The type species, Y. downsi, is named after the late Will Downs, a frequent partaker in paleontological expeditions to China, who died the year before Yinlong was found.

Yinlong is known from a single well-preserved skeleton, complete with skull, of a nearly adult animal, discovered in 2004 in the Shishugou Formation located in Xinjiang Province, China. Yinlong was unearthed in an upper section of the formation which dates to the Oxfordian stage of the Late Jurassic (161 to 156 million years ago). All other known ceratopsians hail form the Cretaceous Period.

A small nasal bone on the end of the upper jaw identifies Yinlong clearly as a ceratopsian, although the skull displays several other features which were previously thought to be unique to pachycephalosaurians. The presence of the features indicated that the dinosaur was part of the larger group Marginocephalia, which contains both the pachycephalosaurs and ceratopsians, although the features have been lost in all known ceratopsians of the Cretaceous Period.

Yinlong also preserved skull features that resemble that of the family Heterodontosauridae, which could provide support for the theory that heterodontosaurids are closely related to marginocephalians. The group containing Marginocephalia and Heterodontosauridae has been named

Yinlong was a small mainly bipedal herbivore, about 4 feet long. It was discovered with seven gastroliths preserved in the abdominal cavity. Gastroliths are stones stored in the digestive tract to help grind plant material. They are also found in other ceratopsians such as Psittacosaurus, and are widely distributed in most other dinosaur groups. Gastroliths are also found in many bird groups of today.

Yinlong was featured in the National Geographic Channel documentary “Dino Death Trap” as a prey item of Guanlong.

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