Tianyulong

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Tianyulong
Temporal range: Late Jurassic, 158.5  Ma
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Tianyulong.jpg
Specimen IVPP V17090, muzzle, hand, feet and tail framed in red
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Family: Heterodontosauridae
Genus: Tianyulong
Zheng et al., 2009
Species:
T. confuciusi
Binomial name
Tianyulong confuciusi
Zheng et al., 2009

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. [1]

Contents

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. [2]

Another specimen, IVPP V17090, was described in 2012. At least four other specimens remain undescribed. [3]

Description

The holotype skeleton, STMN 26-3 Tianyulong holotype.jpg
The holotype skeleton, STMN 26-3

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. [3]

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

Skull diagrams of Heterodontosaurus and Tianyulong Heterodontosaurus and Tianyulong.tif
Skull diagrams of Heterodontosaurus and Tianyulong

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: [4]

Heterodontosauridae 

Echinodon

Abrictosaurus

NHM RU A100

Heterodontosaurus

Lycorhinus

Fruitadens

Tianyulong

Paleobiology

Restoration Tianyulong BW.jpg
Restoration

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 [5] 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 [6] and Beipiaosaurus . [7] The estimated length of the integumentary structures on the tail is about 60 mm which is seven times the height of a caudal vertebra. Their length and hollow nature argue against of them being subdermal structures such as collagen fibers.

Restored skeleton Tianyulong confuciusi.jpg
Restored skeleton

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. If the homology is not supported, it would indicate that these filamentous dermal structures evolved independently in saurischians and ornithischians, as well as in other archosaurs such as the pterosaurs. The authors (in supplementary information to their primary article) noted that discovery of similar filamentous structures in the theropod Beipiaosaurus bolstered the idea that the structures on Tianyulong are homologous with feathers. Both the filaments of Tianyulong and the filaments of Beipiaosaurus were long, singular, and unbranched. In Beipiaosaurus, however, the filaments were flattened. In Tianyulong, the filaments were round in cross section, and therefore closer in structure to the earliest forms of feathers predicted by developmental models. [1]

Related Research Articles

Theropoda Clade of dinosaurs

Theropoda, whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three-toed limbs. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores, omnivores, piscivores, and insectivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago (Ma) and included the sole large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by about 10,500 living species.

Ornithischia Order of dinosaurs

Ornithischia is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name Ornithischia, or "bird-hipped", reflects this similarity and is derived from the Greek stem ornith- (ὀρνιθ-), meaning "of a bird", and ischion (ἴσχιον), plural ischia, meaning "hip joint". However, birds are only distantly related to this group as birds are theropod dinosaurs.

<i>Sinosauropteryx</i>

Sinosauropteryx is a compsognathid dinosaur. Described in 1996, it was the first dinosaur taxon outside of Avialae to be found with evidence of feathers. It was covered with a coat of very simple filament-like feathers. Structures that indicate colouration have also been preserved in some of its feathers, which makes Sinosauropteryx the first non-avialian dinosaurs where colouration has been determined. The colouration includes a reddish and light banded tail. Some contention has arisen with an alternative interpretation of the filamentous impression as remains of collagen fibres, but this has not been widely accepted.

Maniraptora

Maniraptora is a clade of coelurosaurian dinosaurs which includes the birds and the non-avian dinosaurs that were more closely related to them than to Ornithomimus velox. It contains the major subgroups Avialae, Deinonychosauria, Oviraptorosauria and Therizinosauria. Ornitholestes and the Alvarezsauroidea are also often included. Together with the next closest sister group, the Ornithomimosauria, Maniraptora comprises the more inclusive clade Maniraptoriformes. Maniraptorans first appear in the fossil record during the Jurassic Period, and are regarded as surviving today as living birds.

<i>Beipiaosaurus</i>

Beipiaosaurus is a genus of therizinosauroid theropod dinosaurs that lived in Asia during the Early Cretaceous in the Yixian Formation. The first remains were found in 1996 and formally described in 1999. Before the discovery of Yutyrannus, they were among the largest dinosaurs known from direct evidence to be feathered. Beipiaosaurus is known from three reported specimens preserving numerous impressions of feather structures that allowed to determine the feathering color which turned out to be brownish.

Feathered dinosaur

A feathered dinosaur is any species of dinosaur possessing feathers. While this includes all species of birds, recent evidence supports the hypothesis that many, if not all non-avian dinosaur species also possessed feathers in some shape or form. It has been suggested that feathers had originally evolved for the purposes of thermal insulation, as remains their purpose in the down feathers of infant birds today, prior to their eventual modification in birds into structures that support flight.

Therizinosauria

Therizinosaurs were small to giant-sized, mainly herbivorous, theropod dinosaurs that have been found across the Early to Late Cretaceous deposits in Mongolia, China and North America. Various features of the forelimbs, skull and pelvis unite these finds as both theropods and maniraptorans, close relatives to birds. The representative genus, Therizinosaurus, is derived from the Greek θερίζω and σαῦρος. The older representative, Segnosaurus, is derived from the Latin word segnis and the Greek σαῦρος.

<i>Psittacosaurus</i> Ceratopsian dinosaur genus from Early Cretaceous Asia

Psittacosaurus is a genus of extinct ceratopsian dinosaur from the Early Cretaceous of what is now Asia, existing between 126 and 101 million years ago. It is notable for being the most species-rich dinosaur genus. Up to 12 species are known, from across China, Mongolia, Siberia, and possibly Thailand and Laos. The species of Psittacosaurus were obligate bipeds at adulthood, with a high skull and a robust beak. One individual was found preserved with long filaments on the tail, similar to those of Tianyulong, and scales across the rest of the animal. Psittacosaurus probably had complex behaviours, based on the proportions and relative size of the brain. It may have been active for short periods of time during the day and night, and had well-developed senses of smell and vision.

<i>Juravenator</i>

Juravenator is a genus of small coelurosaurian theropod dinosaur, which lived in the area which would someday become the top of the Franconian Jura of Germany, about 151 or 152 million years ago. It is known from a single, juvenile specimen.

Heterodontosauridae

Heterodontosauridae is a family of early ornithischian dinosaurs that were likely among the most basal (primitive) members of the group. Although their fossils are relatively rare and their group small in numbers, they lived across all continents except Australia for approximately 100 million years, from the Late Triassic to the Early Cretaceous.

Compsognathidae

Compsognathidae is a family of coelurosaurian theropod dinosaurs. Compsognathids were small carnivores, generally conservative in form, hailing from the Jurassic and Cretaceous Periods. The bird-like features of these species, along with other dinosaurs such as Archaeopteryx inspired the idea for the connection between dinosaur reptiles and modern-day avian species. Compsognathid fossils preserve diverse integument — skin impressions are known from four genera commonly placed in the group, Compsognathus, Sinosauropteryx, Sinocalliopteryx, and Juravenator. While the latter three show evidence of a covering of some of the earliest primitive feathers over much of the body, Juravenator and Compsognathus also show evidence of scales on the tail or hind legs.

<i>Sinocalliopteryx</i>

Sinocalliopteryx is a genus of carnivorous compsognathid theropod dinosaurs from the Lower Cretaceous Yixian Formation of China.

Evolution of dinosaurs An outline and examples of dinosaur evolution

Dinosaurs evolved with single lineage of archosaurs 243-233 Ma from the Anisian to the Carnian ages, the latter part of the middle Triassic. Dinosauria is a well-supported clade, present in 98% of bootstraps. It is diagnosed by many features including loss of the postfrontal on the skull and an elongate deltopectoral crest on the humerus.

Avifilopluma

Avifilopluma is a clade containing all animals with feathers. Unlike most clades, which are defined based on relative relationships, Avifilopluma is defined based on an apomorphy, that is, a unique physical characteristic shared by one group and not found outside that group. It includes all coelurosaurs, some orionoides, and one or two basal tetanurans.

<i>Concavenator</i> Carcharodontosaurid dinosaur genus from the early Cretaceous period

Concavenator is a genus of theropod dinosaur that lived approximately 130 million years ago during the early Cretaceous period. The type species is C. corcovatus; Concavenator corcovatus means "Cuenca hunter with a hump". The fossil was discovered in the Las Hoyas fossil site of Spain by paleontologists José Luis Sanz, Francisco Ortega and Fernando Escaso from the Autonomous University of Madrid and the National University of Distance Education.

<i>Manidens</i>

Manidens is a genus of heterodontosaurid dinosaur from the Middle Jurassic of Patagonia. Fossils have been found in the Cañadón Asfalto Formation in Chubut Province, Argentina, dating to the Bajocian.

<i>Yutyrannus</i>

Yutyrannus is a genus of proceratosaurid tyrannosauroid dinosaur which contains a single known species, Yutyrannus huali. This species lived during the early Cretaceous period in what is now northeastern China. Three fossils of Yutyrannus huali—all found in the rock beds of Liaoning Province—are currently the largest-known dinosaur specimens that preserve direct evidence of feathers.

<i>Sciurumimus</i>

Sciurumimus is an extinct genus of tetanuran theropod from the Late Jurassic of Germany. It is known from a single juvenile specimen representing the type species, Sciurumimus albersdoerferi, which was found in a limestone quarry close to Painten in Lower Bavaria. The specimen was preserved with traces of feather-like filaments.

<i>Kulindadromeus</i>

Kulindadromeus was a herbivorous dinosaur, a basal neornithischian from the Jurassic. The first Kulindadromeus fossil was found in Russia. Its feather-like integument is evidence for protofeathers being basal to Ornithischia and possibly Dinosauria as a whole, rather than just to Coelurosauria, as previously suspected.

References

  1. 1 2 Zheng, Xiao-Ting; You, Hai-Lu; Xu, Xing; Dong, Zhi-Ming (19 March 2009). "An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures". Nature . 458 (7236): 333–336. doi:10.1038/nature07856. PMID   19295609.
  2. Liu Y.-Q. Kuang H.-W., Jiang X.-J., Peng N., Xu H. & Sun H.-Y. (2012). "Timing of the earliest known feathered dinosaurs and transitional pterosaurs older than the Jehol Biota." Palaeogeography, Palaeoclimatology, Palaeoecology (advance online publication).
  3. 1 2 Sereno, Paul (2012-03-10). "Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs". ZooKeys. 226: 1–225. doi:10.3897/zookeys.226.2840. ISSN   1313-2970. PMC   3491919 . PMID   23166462.
  4. Richard J. Butler, Jin Liyong, Chen Jun, Pascal Godefroit (2011). "The postcranial osteology and phylogenetic position of the small ornithischian dinosaur Changchunsaurus parvus from the Quantou Formation (Cretaceous: Aptian–Cenomanian) of Jilin Province, north-eastern China". Palaeontology. 54 (3): 667–683. doi:10.1111/j.1475-4983.2011.01046.x.CS1 maint: multiple names: authors list (link)
  5. Mayr, Gerald; Peters, D. Stephan; Plodowski, Gerhard; Vogel, Olaf (August 2002). "Bristle-like integumentary structures at the tail of the horned dinosaur Psittacosaurus". Naturwissenschaften . Heidelberg: Springer Berlin. 89 (8): 361–365. doi:10.1007/s00114-002-0339-6. PMID   12435037.
  6. Currie, Philip J.; Pei-ji Chen (2001). "Anatomy of Sinosauropteryx prima from Liaoning, northeastern China". Canadian Journal of Earth Sciences . NRC Canada. 38 (12): 1705–1727. doi:10.1139/cjes-38-12-1705.
  7. Xu, Xing; Zheng Xiao-ting; You, Hai-lu (20 January 2009). "A new feather type in a nonavian theropod and the early evolution of feathers". Proceedings of the National Academy of Sciences . 106 (3): 832–4. doi:10.1073/pnas.0810055106. PMC   2630069 . PMID   19139401.