Tianyulong (Chinese: 天宇龍; Pinyin: tiānyǔlóng; named for the Shandong Tianyu Museum of Nature where the holotype fossil is housed) is an extinct genus of heterodontosaurid ornithischian dinosaur. The only species is T. confuciusi, whose remains were discovered in Jianchang County, Western Liaoning Province, China.
History
The holotype of Tianyulong, STMN 26-3 was initially reported as being from the Early Cretaceous Jehol group. The fossil was collected at a locality transliterated as Linglengta or Linglongta. Lu et al., 2010, reported that these beds were actually part of the Tiaojishan Formation, dating from the late Jurassic period at least 158.5 million years ago.
Another specimen, IVPP V17090, was described in 2012. At least four other specimens remain undescribed.
Description
STMN 26-3 consists of an incomplete skeleton preserving a partial skull and mandible, partial presacral vertebrae, proximal–middle caudal vertebrae, nearly complete right scapula, both humeri, the proximal end of the left ulna, partial pubes, both ischia, both femora, the right tibia and fibula and pes, as well as remains of long, singular and unbranched filamentous integumentary structures. The holotype is from a subadult individual that probably measured 70 cm in length based on the proportions of the related South African species Heterodontosaurus tucki. However, Tianyulong had unusual proportions compared to other heterodontosaurids. The head was large and the legs and tail were long, but the neck and forelimbs were short.
Tianyulong has a row of long, filamentous integumentary structures on the back, tail and neck of the specimen. The similarity of these structures with those found on some theropods suggests their homology with feathers and raises the possibility that the earliest dinosaurs and their ancestors were covered with homologous dermal filamentous structures that can be considered primitive feathers ("proto-feathers").
Classification
Tianyulong is classified as a heterodontosaurid, a group of small ornithischian dinosaur characterized by a slender body, long tail and a pair of enlarged canine-like tusks. They were herbivorous or possibly omnivorous. Until the discovery of Tianyulong, known members of the group were restricted to the Early Jurassic of South Africa, with one genus (Fruitadens) from the Late Jurassic of the US, and possibly one additional genus (Echinodon) from the Early Cretaceous of England.
The cladogram below follows the analysis by Butler et al., 2011: