Tianyulong

Tianyulong
Credit: Unknown
Time Period:	Late Jurassic
Diet:	Presumably Omnivorous
Area:	Eastern Asia; Jianchang County, Western Liaoning Province, China
Scientific classifiation:	heterodontosaurid ornithischian dinosaur
Species:	Tianyulong confuciusi

Tianyulong (Chinese: 天宇龍; Pinyin: tiānyǔlóng; named for the Shandong Tianyu Museum of Nature where the holotype fossil is housed) was a genus of heterodontosaurid ornithischian dinosaur.

The only species was T. confuciusi, whose remains were discovered in Jianchang County, Western Liaoning Province, China.

Discovery

The fossil 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.

Description

A pair of fighting Toanyulongs

Toanyulong 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").

The holotype consists of an incomplete skeleton preserving a partial skull and mandible. 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.

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 USA, and possibly one additional genus (Echinodon) from the Early Cretaceous of England.

The cladogram below follows the analysis by Butler et al., 2011:

Heterodontosauridae	Echinodon Abrictosaurus NHM RU A100 Heterodontosaurus Lycorhinus Fruitadens Tianyulong

Paleobiology

The filamentous integumentary structures are preserved on three areas of the fossil: in one patch just below the neck, another one on the back, and the largest one above the tail. The hollow filaments are parallel to each other and are singular with no evidence of branching.

They also appear to be relatively rigid, making them more analogous to the integumentary structures found on the tail of Psittacosaurus than to the proto-feather structures found in avian and non-avian theropods. Among the theropods, the structures in Tianyulong are most similar to the singular unbranched proto-feathers of Sinosauropteryx and Beipiaosaurus. The estimated length of the integumentary structures on the tail is about 60mm which is seven times the height of a caudal vertebra.

• Such dermal structures have previously been reported only in derived theropods and ornithischians, and their discovery in Tianyulong extends the existence of such structures further down in the phylogenetic tree.

However, the homology between the ornithischian filaments and the theropods' proto-feathers is not obvious. If the homology is supported, the consequence is that the common ancestor of both saurischians and ornithischians were covered by feather-like structures, and that groups for which skin impression are known such as the sauropods were only secondarily featherless.

In Tianyulong, the filaments were round in cross section, and therefore closer in structure to the earliest forms of feathers predicted by developmental models.

Gallery

External links

• Ed Yong (March 18, 2009). "Tianyulong - a fuzzy dinosaur that makes the origin of feathers fuzzier". http://scienceblogs.com/notrocketscience/2009/03/tianyulong_-_a_fuzzy_dinosaur_that_makes_the_origin_of_feath.php.