Sinornithosaurus
| Sinornithosaurus | ||||||||||||
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Sinornithosaurus millenii in the Hong Kong Science Museum |
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| Temporal occurrence | ||||||||||||
| Lower Cretaceous (late Barremian to early Aptian ) | ||||||||||||
| 129.4 to 123 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Sinornithosaurus | ||||||||||||
| Xu , Wang & Wu , 1999 | ||||||||||||
Sinornithosaurus is a genus of theropod dinosaur from the group of Dromaeosauridae . Finds of this animal come from the Yixian Formation ( Lower Cretaceous ) in the Chinese province of Liaoning . Sinornithosaurus was a very bird-like feathered dromaeosaur, which was characterized by the proportionally longest arms of all theropods. As a recent study suggests, this animal likely hunted its prey with poison. This early and basal (original) Dromaeosaurid is mostly a representative of the Dromaeosaurid subgroup Microraptorinae. So far, at least two skeletons are known that are attributed to two species, Sinornithosaurus millenii and Sinornithosaurus haoiana . Another skeleton with the nickname "Dave" may also belong to this genus.
features
Sinornithosaurus was a small dromaeosaurid. The type specimen was estimated to be 128 cm long and 5 kg, with the skull about 15.2 cm and the femur (thigh bone) about 14.8 cm long.
The skull of the type specimen is almost completely preserved, although most of the bones of the find are no longer in the anatomical bond. As with all dromaeosaurids, the skull was lightly built and showed a large cranial skull and a narrow snout. The snout was about 7.5 cm long and proportionally shorter than that of Velociraptor and Deinonychus . The arms were the proportionally longest of all non-avian theropods and are estimated to be 80% of the hind leg length. The shape of the metatarsal bones suggests that the metatarsus of Sinornithosaurus was designed as an arctometatarsus : The third (middle) metatarsal bone is strongly tapered in the upper section and has a triangular cross-section in the lower section. This feature can only be found among dromaeosaurids in Microraptor .
Autapomorphies , i.e. features by which the genus can be distinguished from other genera, can be found on different parts of the skeleton: The antorbital fossa in front of the large eye sockets was large , as in other dromaeosaurids, but in contrast to other genera showed a number in the front area at ornament-like pits and hills. The os coracoides (raven bone) shows a window, which has meanwhile also been detected in Microraptor . Other diagnostic features include the large breastbone (sternum).
The shoulder girdle in particular showed strong similarities with that of early birds and supports the theory that the Dromaeosauridae were more closely related to birds than any other known dinosaur group. For example, the fork leg (furcula) was shaped like a boomerang, similar to Archeopteryx , but different from, for example, Velociraptor . Other very bird-like features can be found in the pelvic and hind leg region.
Feathers and possible poisonous bite
The type specimen of Sinornithosaurus millenii shows 30 to 45 mm long and 1 to 3 mm wide filament structures that are interpreted as feathers. The find shows both tuft-like feathers, in which the filaments converge at one point, and filaments that run along a central shaft. The possible Sinornithosaurus find NGMC 91 ("Dave") shows feathers all over the body, with the exception of the lower sections of the legs.
A recent study by Gong and colleagues (2009) discovered evidence of a poisonous bite in the type specimen of Sinornithosaurus millenii : In addition to unusual dentition, the skeleton shows notched teeth, a cavity, which presumably represented a poison gland, and a canal from this Poison gland led to the base of the tooth. These characteristics are analogous to today's poisonous lizards. The researchers suspect that Sinornithosaurus and related dromaeosaurids may have hunted birds.
Another team of scientists, led by Federico Gianechini, published a study in 2010 that casts doubt on the toxicity of Sinornithosaurus . They showed that notches in the teeth are by no means unique to this genus, but also occur in many other theropods, especially in other representatives of the Dromaeosauridae . They also noted that the teeth were not unusually long, as Gong and his team claimed, but merely slipped out of the tooth sockets - an artifact that often occurs with fossils that are flattened. Ultimately, they were unable to verify the existence of a poison gland chamber, as Gong and his team postulated.
In the same issue of the magazine, Gong and colleagues responded to the criticism. They admitted that serrated teeth were perfectly normal among theropods (although they noted that they were arguably only common in the feathered Maniraptora ). They then hypothesized that poison might have been a primitive feature of all Archosauria , if not all reptiles, that was only preserved in a few lines of evolution. They also resisted the statement that the Sinornithosaurus holotype's teeth were driven far out of the jaw, although they admitted that the teeth are not in their natural position. Gong further claimed that some undescribed specimens, whose teeth are preserved in conjunction with the jaw, show the same tooth length.
Finds and naming
The first find ( holotype , specimen number IVPP V.12811) comes from Sihetun , a famous site for fossil fish, birds and dinosaurs in western Liaoning . Stratigraphically , the skeleton comes from layer 6 of the lower Yixian formation of the Jehol group . In 1999 the find was scientifically described by Xu, Wang and Wu as Sinornithosaurus millenii . Sinornithosaurus ( gr. Sinai , lat. Sinae - "Chinese"; gr. Ornis - "bird"; gr. Sauros - "lizard") means something like "Chinese bird lizard", while the Artepitheth millenii (lat. Millennium ) refers to the This animal was discovered shortly before the turn of the millennium .
A second species, Sinornithosaurus haoiana ("Hao's Sinornithosaurus "), was described by Liu and colleagues in 2004. It is based on a new skeleton that differs from Sinornithosaurus millenii in the skull and pelvic area.
Another possible Sinornithosaurus find (specimen number NGMC 91) was described by Qiang and colleagues in 2001 and is nicknamed "Dave". The find was discovered in the Fanzhangzi quarry, 20 km southwest of Lingyuan , in Liaoning. This skeleton is complete and anatomically combined on two stone slabs, the first stone slab showing the bones and the second showing the impressions of the bones. When the original plate was split apart when collecting fossils, most of the very brittle bones were broken, which is why many anatomical details can no longer be adequately examined. “Dave” shows some differences from Sinornithosaurus , such as an unusually curved first metatarsal bone - some of these differences could, however, be attributed to individuals of different ages. Near the left foot of the skeleton is a fossil of the small fish Lycoptera .
literature
- Xing Xu , Xiao-Lin Wang, Xiao-Chun Wu: A dromaeosaurid dinosaur with a filamentous integument from the Yixian Formation of China. In: Nature . Vol. 401, No. 6750, 1999, pp. 262-266, doi : 10.1038 / 45769 .
Web links
Individual evidence
- ↑ a b Xing Xu, Xiao-Chun Wu: Cranial morphology of Sinornithosaurus millenii Xu et al. 1999 (Dinosauria: Theropoda: Dromaeosauridae) from the Yixian Formation of Liaoning, China. In: Canadian Journal of Earth Sciences. Vol. 38, No. 12, 2001, ISSN 0008-4077 , pp. 1739-1752, doi : 10.1139 / e01-082 .
- ^ Alan H. Turner, Diego Pol, Julia A. Clarke, Gregory M. Erickson, Mark A. Norell : A Basal Dromaeosaurid and Size Evolution Preceding Avian Flight. In: Science . Vol. 317, No. 5843, 2007, pp. 1378–1381, doi : 10.1126 / science.1144066 , digitized version (PDF; 504 kB) .
- ↑ Xing Xu, Xiao-Lin Wang: Troodontid-like pes in the dromaeosaurid Sinornithosaurus. In: Journal of the Paleontological Society of Korea, Special Publication. No. 4, 2000, pp. 179–188 ( PDF 878 kB)
- ↑ Xing Xu, Zhonghe Zhou , Xiaolin Wang: The smallest known non-avian theropod dinosaur. In: Nature. Vol. 408, No. 6813, 2000, pp. 705-708, doi : 10.1038 / 35047056 .
- ↑ Xing Xu, Zhonghe Zhou, Xiaolin Wang, Xuewen Kuang, Fucheng Zhang, Xiangke Du: Four-winged dinosaurs from China. In: Nature. Vol. 421, No. 6921, 2003, pp. 335-340, doi : 10.1038 / nature01342 .
- ↑ Mark Norell, Peter Makovicky : Dromaeosauridae. In: David B. Weishampel , Peter Dodson , Halszka Osmólska (eds.): The Dinosauria . 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , p. 208.
- ↑ Xing Xu, Zhong-he Zhou, Richard O. Prum: Branched integumental structures in Sinornithosaurus and the origin of feathers. In: Nature. Vol. 410, No. 6825, 2001, pp. 200-204, doi : 10.1038 / 35065589 .
- ^ A b Qiang Ji, Mark A. Norell, Ke-Qin Gao, Shu-An Ji, Dong Ren: The distribution of integumentary structures in a feathered dinosaur. In: Nature. Vol. 410, No. 6832, 2001, pp. 1084-1087, doi : 10.1038 / 35074079 .
- ↑ Enpu Gong, Larry D. Martin , David A. Burnham, Amanda R. Falk: The birdlike raptor Sinornithosaurus was venomous. In: Proceedings of the National Academy of Sciences . Vol. 107, No. 2, 2010, pp. 766-768, doi : 10.1073 / pnas.0912360107 .
- ↑ Federico A. Gianechini, Federico L. Agnolín, Martín D. Ezcurra: A reassessment of the purported venom delivery system of the bird-like raptor Sinornithosaurus. In: Paleontological Journal . Vol. 85, No. 1, 2011, pp. 103-107, doi : 10.1007 / s12542-010-0074-9 .
- ↑ Enpu Gong, Larry D. Martin, David A. Burnham, Amanda R. Falk: Evidence for a venomous Sinornithosaurus. In: Paleontological Journal. Vol. 85, No. 1, 2011, pp. 109-111, doi : 10.1007 / s12542-010-0076-7 .
- ↑ Ben Creisler: Dinosauria Translation and Pronunciation Guide. Archived from the original on July 20, 2011 ; Retrieved December 25, 2009 .
- ↑ Liu Jinyuan, Ji Shuan, Tang Feng, Gao Chunling: A new species of dromaeosaurids from the Yixian Formation of western Liaoning. In: Geological Bulletin of China. Vol. 23, No. 8, 2004, ISSN 1671-2552 , pp. 778-789.