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Skull of Yinlong

Skull of Yinlong

Temporal occurrence
Upper Jurassic ( Oxfordium )
163.5 to 157.3 million years
Dinosaur (dinosauria)
Pelvic dinosaur (Ornithischia)
Scientific name
Xu et al., 2006
Reconstruction of Yinlong

Yinlong is a genus of pelvic dinosaurs (Ornithischia) from the Ceratopsia group . He is the oldest and most primeval known representative of this group. But it also shows some features of the Pachycephalosauria and thus underpins the presumed close relationship between these two groups of dinosaurs. Yinlong lived in the Upper Jurassic in East Asia. The only species described is Y. downsi Xu et al., 2006.


Of Yinlong one, except for the tail complete specimen was found so far. It was four feet long, but it was probably not quite grown. The hind legs were strong and strong, the front legs, which were only 40% of the length of the hind limbs, thin and delicate. Yinlong was probably moving biped .

There was a rostral bone at the tip of the upper jaw , which clearly classifies this dinosaur as a representative of the Ceratopsia. The scaly bone (Squamosum) is characterized by a series of small bony bumps, which is also a feature of the Pachycephalosauria. It forms a narrow neck shield, in contrast to the later Ceratopsia, the parietal bone (parietal) is not involved in the neck shield.

On the intermaxillary bone (premaxillary) there are three teeth per side and on the upper jaw (maxilla) there are 13 teeth per side. The teeth of the intermaxillary bone are significantly larger, the second tooth is slightly jagged. The maxillary teeth are close together and are chisel-shaped. Due to the closed jaw, the teeth of the lower jaw can barely be seen, but the front ones are significantly smaller than the back ones.

Seven gastroliths , each 1 to 1.5 centimeters in diameter, were found in the area of ​​the trunk . Compared to the dimensions of the animal, these are strikingly large, similar to the Psittacosauridae .

Discovery and dating

The fossil remains of Yinlong were discovered in the Shishugou Formation in the Djungarian Basin in Xinjiang , China , and were first described by Xu Xing in 2006. The generic name is derived from the Chinese words Yǐn ( Chinese    /   - "hidden") and Lóng (  /   - "dragon"). This is an allusion to the movie Crouching Tiger, Hidden Dragon , which was partly shot near the place where it was found. Long (= "dragon") is also a common part of the name of dinosaurs found in China, such as Dilong or Guanlong . Type species and the only known species is Y. downsi , the specific epithet honors the paleontologist Will Downs, who died shortly before the name was given.

The finds are dated in the early Upper Jurassic in the Oxfordian to an age of about 163 to 157 million years. Yinlong is therefore the oldest known Ceratopsia , making this group around 20 million years older than previously assumed.


The Yinlong find secures the relationship between the Ceratopsia and the Pachycephalosauria .

Characteristics such as the rostral bone clearly classify Yinlong as a representative of the Ceratopsia . It differs from other Ceratopsia, however, among other things by a proportionally smaller head, the less protruding Jugale (a skull bone), the exclusion of the parietal bone from the neck shield and other features in the structure of the skull. The first descriptors therefore classify it as the most basic representative of this dinosaur group.

At the same time, however , Yinlong also shows features of the Pachycephalosauria , a group of stubborn dinosaurs that are predominantly found in the Upper Cretaceous. Even before Yinlong was discovered , ceratopsia and pachycephalosauria were considered closely related and were grouped together as marginocephalia . Due to the high specialization of both groups of dinosaurs, this relationship was so far only weakly secured by morphological features. According to the first descriptions, the discovery of Yinlong clearly confirms the monophyly of Marginocephalia.

Another, albeit surprising, conclusion of the first description is that Yinlong also has similarities with the Heterodontosauridae . In most of the more recent classifications, including Weishampel et al. (2004), the Heterodontosauridae are assigned to the Ornithopoda , a group of dinosaurs with a large number of shapes, including the Iguanodon and the Hadrosauridae . According to these classifications, Ornithopoda and Marginocephalia are considered sister groups . Xu et al. however, summarize the Marginocephalia and the Heterodontosauridae as Heterodontosauriformes and list cranial features (the temporal region and the region in front of the eye) and features in the structure of the teeth (such as the enlarged teeth of the intermaxillary bone ) as similarities. Xu et al. present a phylogenetic investigation, according to which the Heterodontosauriformes are embedded in the Ornithopoda. That would make the Ornithopoda in the traditional sense (excluding the Marginocephalia) a paraphyletic group. It remains to be seen whether this view will prevail.


Web links

Commons : Yinlong  - collection of images, videos and audio files

Individual evidence

  1. ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , p. 244, online .