Tianyuraptor

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Tianyuraptor
Temporal range: Early Cretaceous, 122  Ma
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Tianyuraptor.jpg
Holotype specimen
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Dromaeosauridae
Clade: Microraptoria
Genus: Tianyuraptor
Zheng et al. 2009
Species:
T. ostromi
Binomial name
Tianyuraptor ostromi
Zheng et al., 2009

Tianyuraptor is a genus of short-armed dromaeosaurid dinosaur ('running lizard'; a type of small dinosaur considered to be closely related to birds) that lived during the Early Cretaceous, about 122 million years ago. Its remains have been found in western Liaoning, China. It was similar to other dromaeosaurids found in Liaoning, with the exception of being somewhat more primitive. The type specimen, formally named in 2009, shows features not seen in previously known Northern Hemisphere (Laurasian) dromaeosaurids, but present in Southern Hemisphere (Gondwanan) species and early birds. Because of this, the scientists who first studied Tianyuraptor described it as a "transitional species", bridging the gap between northern and southern types of dromaeosaurid. Tianyuraptor also differs from previously known dromaeosaurids in that it possesses a relatively small furcula ("wishbone"), and unusually short forelimbs. [1]

A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.

Dromaeosauridae family of reptiles (fossil)

Dromaeosauridae is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek δρομεῦς meaning 'runner' and σαῦρος meaning 'lizard'. In informal usage they are often called raptors, a term popularized by the film Jurassic Park; a few types include the term "raptor" directly in their name and have come to emphasize their bird-like appearance and speculated bird-like behavior.

Dinosaur Superorder of reptiles (fossil)

Dinosaurs were a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201 million years ago; their dominance continued through the Jurassic and Cretaceous periods. The fossil record demonstrates that birds are modern feathered dinosaurs, having evolved from earlier theropods during the late Jurassic Period. As such, birds were the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event 66 million years ago. Dinosaurs can therefore be divided into avian dinosaurs, or birds; and non-avian dinosaurs, which are all dinosaurs other than birds. This article deals primarily with non-avian dinosaurs.

Contents

Etymology

The generic name of Tianyuraptor combines Tianyu, referring to the Shandong Tianyu Museum of Nature where the holotype specimen is stored, with raptor, the Latin word for 'robber', referring to the action of grabbing prey, often used in naming dromaeosaurids. The specific epithet, ostromi, is in honor of John Ostrom, [1] who contributed greatly to the study of dromaeosaurid fossils, including Deinonychus and feathered dinosaurs. [2] [3]

Holotype The example of an organism used to describe its species

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype. Under the International Code of Zoological Nomenclature (ICZN), a holotype is one of several kinds of name-bearing types. In the International Code of Nomenclature for algae, fungi, and plants (ICN) and ICZN the definitions of types are similar in intent but not identical in terminology or underlying concept.

In zoological nomenclature, the specific name is the second part within the scientific name of a species. The first part of the name of a species is the name of the genus or the generic name. The rules and regulations governing the giving of a new species name are explained in the article species description.

John Ostrom American paleontologist

John Harold Ostrom was an American paleontologist who revolutionized modern understanding of dinosaurs in the 1960s.

Description

Artist's life restoration Tianyuraptor restoration.png
Artist's life restoration

Tianyuraptor is a medium-sized dromaeosaurid that has several derived features that separate it from other dromaeosaurids. These include the length of the middle caudal (tail) vertebrae being more than twice that of the dorsal (back) vertebrae, a small and extremely slender furcula, and an unusually long hindlimb that is roughly three times as long as the entire series of dorsal vertebrae. As in other dromaeosaurid fossils discovered in Liaoning, [4] the tail is relatively long at 960 millimetres (38 in), nearly 4.8 times as long as the femur. [1]

Furcula

The furcula or wishbone is a forked bone found in birds and some dinosaurs, and is formed by the fusion of the two clavicles. In birds, its primary function is in the strengthening of the thoracic skeleton to withstand the rigors of flight.

The type specimen is STM1–3, a nearly complete and fully articulated skeleton that is only missing the extreme distal end of the tail. A total of 25 fully articulated caudal vertebrae are preserved and at the end three at most are estimated to be missing. The fossil was discovered in the Dawangzhangzi Bed of the Yixian Formation (Jehol Group), located in Lingyuan in western Liaoning, China. [1] The Yixian Formation is an Early Cretaceous rock unit, dated to between approximately 129.7 and 122.1 million years old, in the Barremian and Aptian faunal stages. [5] The Dawangzhangzi Bed specifically has been dated to about 122 million years ago. [6] STM1–3 is believed to be a sub-adult, with features including the incomplete fusion of skeletal parts during ontogeny. The holotype of Tianyuraptor preserves no soft tissues, unlike many other theropod specimens from the Jehol Group. [1]

Fossil Preserved remains or traces of organisms from a past geological age

A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood, oil, coal, and DNA remnants. The totality of fossils is known as the fossil record.

Yixian Formation Rock formation

The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period. It is known for its exquisitely preserved fossils, and is mainly composed of basalts interspersed with siliciclastic sediments.

Liaoning Province

Liaoning is a northern coastal province in Northeast China on the shore of Yellow Sea, being the smallest but the most populous province in the region. The modern Liaoning province was established in 1907 as Fengtian or Fengtien province and was renamed Liaoning in 1929, also known as Mukden Province at the time for the Manchu pronunciation of Shengjing, the former name of the provincial capital Shenyang. Under the Japanese-puppet Manchukuo regime, the province reverted to its 1907 name, but the name Liaoning was restored in 1945 and again in 1954.

Limbs

The forelimbs are comparatively short, being only 53% of the hindlimbs' length. This differs greatly from the known skeletal elements of other dromaeosaurids, most of which have relatively long forelimbs that are more than 70% of the hindlimbs' length. [1]

While Tianyuraptor is larger in size than all other known microraptorines, it also has relatively elongated lower hindlimbs, like other microraptorines. In this regard, it is different from most other dromaeosaurids, which have relatively short lower legs. [7] For example, Tianyuraptor has a tibiotarsus/femur length ratio of greater than 1.30, while Velociraptor mongoliensis , a creature of similar size, exhibits a ratio of less than 1.10. [8] Aside from elongate hind limbs, Tianyuraptor is different from other members of Microraptorinae in regards to the relative lengths of the forelimb elements. The forelimbs of Tianyuraptor are proportionally much shorter than those of larger dromaeosaurids. For example, a similar-sized Velociraptor specimen shows an arm/leg length ratio of approximately 0.75., while Tianyuraptor has an arm/leg ratio of 0.53. [1]

Tibiotarsus

The tibiotarsus is the large bone between the femur and the tarsometatarsus in the leg of a bird. It is the fusion of the proximal part of the tarsus with the tibia.

<i>Velociraptor</i> genus of reptiles (fossil)

Velociraptor is a genus of dromaeosaurid theropod dinosaur that lived approximately 75 to 71 million years ago during the latter part of the Cretaceous Period. Two species are currently recognized, although others have been assigned in the past. The type species is V. mongoliensis; fossils of this species have been discovered in Mongolia. A second species, V. osmolskae, was named in 2008 for skull material from Inner Mongolia, China.

Paleobiology

The stark difference in arm length compared to other dromaeosaurids implies that the function of the arms in Tianyuraptor was different from that of other dromaeosaurs. Members of the subfamily Microraptorinae, such as Microraptor , have been suggested to have been aerodynamic and may have glided. [9] [10] Microraptorines are usually noted for their long and robust forelimbs and large, asymmetrical flight feathers. However, the shortened forelimbs, small furcula, and the transversely wide coracoid in Tianyuraptor suggest that it was not suited for aerodynamic gliding or flight.

Classification

A phylogenetic analysis performed by Zheng et al. showed Tianyuraptor to be a basal member of a group containing Laurasian dromaeosaurids. Tianyuraptor seems to possess several features that are unknown in other Laurasian dromaeosaurids, but which are seen in basal avialans and Gondwanan dromaeosaurids, including Austroraptor , Buitreraptor , Neuquenraptor , Rahonavis , and Unenlagia . Zheng and colleagues also noted that Tianyuraptor shares some features with the monophyletic subfamily Microraptorinae, though they went on to say that this mixture of features suggests a basal placement for Tianyuraptor within Microraptorinae, as evidenced by their phylogenetic analysis which indicated maximum parsimony in six of the 30 results recovered by the analysis. The authors then go on to suggest that since Tianyuraptor is considered a short-armed microraptorine, more derived long-armed microraptorines might have independently evolved flight capability. However, it is also equally possible, as argued by Zheng et al., that Tianyuraptor may in fact be a basal member of a clade containing all other Laurasian dromaeosaurids with the exception of Microraptorinae. This is indicated by the other 24 out of 30 most parsimonious trees recovered from the analysis. The discovery of Tianyuraptor sheds new light on the early evolution of dromaeosaurs and further exemplifies the great diversity this group enjoyed at an early stage. [1]

See also

Related Research Articles

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Microraptor is a genus of small, four-winged paravian dinosaurs. Numerous well-preserved fossil specimens have been recovered from Liaoning, China. They date from the early Cretaceous Jiufotang Formation, 120 million years ago. Three species have been named, though further study has suggested that all of them represent variation in a single species, which is properly called M. zhaoianus. Cryptovolans, initially described as another four-winged dinosaur, is usually considered to be a synonym of Microraptor.

<i>Beipiaosaurus</i> genus of reptiles (fossil)

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<i>Sinornithosaurus</i> genus of reptiles (fossil)

Sinornithosaurus is a genus of feathered dromaeosaurid dinosaur from the early Cretaceous Period of the Yixian Formation in what is now China. It was the fifth non–avian feathered dinosaur genus discovered by 1999. The original specimen was collected from the Sihetun locality of western Liaoning. It was found in the Jianshangou beds of the Yixian Formation, dated to 124.5 million years ago. Additional specimens have been found in the younger Dawangzhangzi bed, dating to around 122 million years ago.

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<i>Adasaurus</i> genus of reptiles (fossil)

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<i>Zhongjianosaurus</i> Zhongjianosaurus page

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<i>Daliansaurus</i> genus of reptiles (fossil)

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<i>Serikornis</i> genus of all dinosaurs which are more closely related to birds than to oviraptorosaurs

Serikornis is a genus of small, feathered anchiornithid dinosaur from the Upper Jurassic Tiaojishan Formation of Liaoning, China. It is represented by the type species Serikornis sungei. Its name means "Ge Sun's silk bird", a reference to the plumulaceous-like body covering evident in the fossil. The specimen's nickname, "Silky", refers to the striking resemblance of the delicate hindlimb filaments to the modern Silky breed of domestic chicken.

References

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  10. Chatterjee, S.; Templin, R. J. (2007). "Biplane wing planform and flight performance of the feathered dinosaur Microraptor gui". Proceedings of the National Academy of Sciences USA. 104 (5): 1576–1580. doi:10.1073/pnas.0609975104. PMC   1780066 . PMID   17242354.