Tianyuraptor

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Tianyuraptor
Temporal range:
Ma
↓
Holotype specimen
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: 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

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]

Etymology

The

feathered dinosaurs.[2][3]

Description

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]

The

theropod specimens from the Jehol Group.[1]

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

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]

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

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

References

  1. ^
    PMID 19692406
    .
  2. ^ Ostrom, John H. (1969). "Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana". Bulletin of the Peabody Museum of Natural History. 30: 1–165.
  3. ^ "At Last, His Theory Flies". May 5, 2000. Olivia F. Gentile. Hartford Courant.
  4. ^ Senter, P.; Barsbold, R.; Britt, B. B.; Burnham, D. A. (2004). "Systematics and evolution of Dromaeosauridae (Dinosauria, Theropoda)". Bull. Gunma Mus. Nat. Hist. 8: 1–20.
  5. doi:10.1016/j.palaeo.2009.06.021
    .
  6. doi:10.1002/gj.1045
    .
  7. ^ Currie, P. J. (1997). "Dromaeosauridae." Pp. 194–195 in Currie, P.J. and Padian, K. (eds.) Encyclopedia of Dinosaurs. San Diego: Academic Press.
  8. ^ Norell, M. A.; Makovicky, P.J. (1999). "Important features of the dromaeosaurid skeleton. Information from newly collected specimens of Velociraptor mongoliensis". American Museum Novitates (3282): 1–45.
  9. S2CID 1160118
    .
  10. PMID 17242354
    .
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