Tianyulong (named for the Shandong Tianyu Museum of Nature where the holotype fossil (STMN 26-3) is housed) is a genus of basal heterodontosaurid ornithischian dinosaur. The fossil represents a sub-adult individual, approximately 1 meter long. It is notable for the row of long, filamentous integumentary structures apparent on the back, tail and neck of the fossil. The similarity of these structures with those found on some derived theropods suggests their homology with feathers and raises the possibility that the earliest dinosaurs and their ancestors were covered with analogous dermal filamentous structures that can be considered as primitive feathers (proto-feathers). The only species is T. confuciusi, whose remains were discovered in Jianchang County, Western Liaoning Province, China, f