[1][2] A coalition of American and Chinese paleontologists, including Xu Xing, Catherine Forster, Jim Clark, and Mo Jinyou, described and named Yinlong in 2006.

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.

[2] The first specimen discovered was a single exceptionally well-preserved skeleton, complete with skull, of a nearly adult animal, found in 2004 in the Middle-Late Jurassic strata of the Shishugou Formation located in Xinjiang Province, China.

[7] Albalophosaurus Psittacosaurus lujiatunensis Psittacosaurus mongoliensis Stenopelix valdensis Yinlong downsi Chaoyangsaurus youngi Xuanhuaceratops niei Hualianceratops wucaiwanensis Liaoceratops yanzigouensis Archaeoceratops oshimai Koreaceratops hwaseongensis Yamaceratops dorngobiensis Aquilops americanus Auroraceratops rugosus Mosaiceratops azumai Leptoceratops gracilis Bagaceratops rozhdestvenskyi Protoceratops andrewsi 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.