Belonging to the infraorder Ceratopsia, the Yinlong dinosaur (Yinlong downsi) is a small-bodied dinosaur that inhabited what is now China during the Early Jurassic period, approximately 200 million years ago. The name "Yinlong" translates to "hidden dragon". The fossil remains of Yinlong were first discovered in 2005 in the Yunnan Province, providing scientists with invaluable insights into the early evolution of dinosaurs.

Measuring around 1.2 meters in length, Yinlong is relatively small compared to its later relatives, such as Triceratops. Its unique skeletal features include a beak-like mouth, sharp teeth, and a crest on its skull. This cranial ornamentation, reminiscent of later ceratopsians, is thought to have played a role in species recognition, sexual display, or defense. Furthermore, Yinlong possessed long hind limbs, indicating its ability to move swiftly.