Tianyuraptor
| Tianyuraptor | ||||||||||||
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Live reconstruction of Tianyuraptor ostromi |
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| Temporal occurrence | ||||||||||||
| Lower Cretaceous ( Barremium ) | ||||||||||||
| 130.7 to 126.3 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Tianyuraptor | ||||||||||||
| Zheng et al. , 2009 | ||||||||||||
| Art | ||||||||||||
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Tianyuraptor is a genus of theropod dinosaur from the group of Dromaeosauridae . So far, a single, almost complete skeleton is known that comes from the Jehol group in western Liaoning ( China ) and is dated to the Middle Lower Cretaceous ( Barremium ).
The only species , Tianyuraptor ostromi , was described by Zheng and colleagues in 2009 . In contrast to other dromaeosaurids, Tianyuraptor has unusually short arms and a relatively small fork bone (furcula). It is considered a basal (original) dromaeosaurid and could be the most basal representative of the dromaeosaurid subgroup Microraptorinae.
features
Tianyuraptor was a medium-sized dromaeosaurid. The only known specimen was not yet fully grown, as can be seen from the degree of fusion of various skeletal parts. In contrast to many other finds from the Jehol group, there are no remains of soft tissue or feathers.
The skull was large and longer than the femur (thigh bone). The tail was about 4.8 times longer than the femur and therefore relatively long, similar to that of other microraptorins. The cervical vertebrae were about the same length as the dorsal vertebrae - in contrast to other microraptorins, which showed proportionally longer cervical vertebrae. An important autapomorphy , i.e. a characteristic by which the genus can be distinguished from related genera, is shown in the middle caudal vertebrae, which were more than twice as long as the posterior vertebrae.
Tianyuraptor exhibited very short and thin arms that were only 53% of the length of the hind legs. In contrast, other dromaeosaurids have very long arms, which usually account for more than 70% of the hind leg length. Another autapomorphy is the proportionally very long hind legs, which were about three times as long as the spine. The tibiotarsus (lower leg and upper bones of the foot) was 135% of the length of the femur, and was relatively much longer than other, similarly sized dromaeosaurids.
The fork bone (furcula) was extremely slender and very small, so it was only a fifth of the length of the femur. The shoulder blade (scapula) was relatively short and robust, it was not fused with the coracoid (raven bone). The roughly rectangular coracoid lacked the large window that other microraptorins showed.
Systematics
Tianyuraptor is considered a very basal dromaeosaurid. This genus shows some features that were typical for the Unenlagiinen - basal dromaeosaurids Gondwanas - but were missing in the dromaeosaurids of Laurasias . Dromaeosaurids from the Jehol group Liaonings, such as Sinornithosaurus , Microraptor and Graciliraptor , are grouped together within the monophyletic taxon Microraptorinae. Tianyuraptor showed some synapomorphies (jointly derived features) of the Microraptorins, such as the clearly shortened phalanx III-2. Many microraptorine synapomorphies were missing in Tianyuraptor , including the large oval window of the croacoid.
Tianyuraptor could have been the most basic Microraptorine. While some Microraptorins are thought to be capable of gliding or even active flight, the short arms and the small wishbone of Tianyuraptor show that this genus was not capable of flight. If Tianyuraptor was indeed an early Microraptorin, that could indicate that the Microraptorins' ability to fly evolved independently of other groups such as birds. According to another idea, Tianyuraptor could not have been a Microraptorine at all, but the most basic representative of all Dromaeosaurs Laurasias with the exception of the Microraptorinae.
Find and naming
The only known skeleton ( holotype , specimen number STM1-3) was discovered in Lingyuan in western Liaoning . Stratigraphically the Fund comes from the Lower Cretaceous of the Yixian Formation . The find is an almost complete skeleton, probably only missing the three rear caudal vertebrae.
The name Tianyuraptor refers to the Tianyu Museum of Nature , which keeps the fossil; raptor is Latin for "predator". The Artepitheth ostromi honors the important palaeontologist John Ostrom , who has made important work on dromaeosaurids.
literature
Unless otherwise noted, all information comes from the following work:
- Xiaoting Zheng, Xing Xu , Hailu You, Qi Zhao, Zhiming Dong : A short-armed dromaeosaurid from the Jehol Group of China with implications for early dromaeosaurid evolution. In: Proceedings of the Royal Society. Series B: Biological Sciences. Vol. 277, No. 1679, 2010, ISSN 0080-4649 , pp. 211-217, doi : 10.1098 / rspb.2009.1178 .
Individual evidence
- ^ The Paleobiology Database: Tianyuraptor