Gigantoraptor
| Gigantoraptor | ||||||||||||
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Live reconstruction of Gigantoraptor erlianensis |
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous ( Santonium ) | ||||||||||||
| 86.3 to 83.6 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Gigantoraptor | ||||||||||||
| Xu et al. , 2007 | ||||||||||||
| Art | ||||||||||||
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Gigantoraptor was a theropod dinosaur from the group of Oviraptorosauria , which is fossilized from the Upper Cretaceous China . The only known species ( type species ) of this genus , Gigantoraptor erlianensis , was first described in 2007. With an estimated weight of 1.4 tons, Gigantoraptor was an exceptionally large representative of the Oviraptorosauria, a group of bird-like, probably omnivorous dinosaurs whose weight rarely exceeded 40 kilograms. Within the Oviraptorosauria, Gigantoraptor is listed as a basic (original) representative of the Oviraptoridae .
Find and naming
The only specimen so far was discovered in Saihangaobi in Inner Mongolia . The first bone, a thigh bone (femur), was discovered by the "dinosaur hunter" Xing Xu in 2005 while filming a documentary about the discovery of a previous find, a sauropod . When he picked up the fossil to demonstrate the discovery of new fossils, he thought it was another sauropod fossil - but minutes later it became clear that it was a theropod bone.
Stratigraphically , the find comes from the Iren-Dabasu Formation and is dated to the Upper Cretaceous ( Santonium ). It is an incomplete skeleton (holotype, catalog number LH V001), which consists of an almost complete lower jaw, an almost complete right shoulder blade (scapula), most of the arms, almost complete legs, pelvic bones (an almost complete pubic bone and a fragmentary iliac bone ), most of the caudal vertebrae, and some presacral vertebrae (vertebrae in front of the sacrum ). Gigantoraptor was the largest known theropod of the Iren Dabasu fauna and is only surpassed in size by Sonidosaurus , the only known sauropod of this fauna.
The name Gigantoraptor means "gigantic predator" and alludes to the size of the animal, while the species epitheth erlianensis refers to the Erlian basin, where the skeleton was discovered.
features
Gigantoraptor is the largest known Oviraptoraptor with an estimated length of 8 meters and a waist height of 3.5 meters. The weight is estimated at 1400 kilograms - a mathematical formula according to Anderson et al. (1985) is used: . Cf is the minimum circumference of the thighbone (femur) and is 349 mm for Gigantoraptor . Like all Oviraptorosaurs, Gigantoraptor had a likely toothless, deep jaw that was probably covered by a horn beak. The found lower jaw shows both basal features of early oviraptorosaurs and derived features of specialized oviraptorids. When viewed from above, the lower jaws were arranged in a U-shape and completely fused at the seam (symphysis) so that the seam was not visible.
As with other oviraptorosaurs, the caudal vertebrae were pneumatized, that is, they had cavities. However, unlike other Oviraptorosauria, gigantoraptor showed a pair of openings (foramia) on the sides and a large opening on the underside of the vertebral centers of the anterior caudal vertebrae. The vertebral centers of the posterior caudal vertebrae showed a sponge-like structure, so they were criss-crossed with many small chambers - this feature is also shown in a similar form in the Titanosauria and was probably an adaptation for weight reduction. The length ratio of the leg bones differed significantly from other theropods of similar size and is interpreted as an adaptation to fast running.
Other features of gigantoraptor were previously unknown in oviraptorosaurs, but appeared in later, more derived Maniraptora. For example, the distal end of the shoulder blade was not widened, the arms were relatively long, and the first metacarpal was small and less than 1/3 the length of the second metacarpal.
Paleobiology
The researchers made a thin section from a sample of the fibula and examined the growth rings of this bone ( bone histology ). From the number of growth rings, it was possible to determine a probable age at death of 11 years for this individual. Further conclusions can be drawn, among other things, from the distances between individual growth rings: The animal was probably still at a relatively early adult age, which would mean that an adult giant toraptor would have an even higher weight than this one, approx. 4 tons heavy individual could have reached. The animal likely reached early adulthood by age 7. The growth rate of Gigantoraptor , at 128 to 140 kg per year, is higher than that of most other theropods, including the tyrannosaurids .
Since basal oviraptorosaurs like Caudipteryx and Protarchaeopteryx were pinnate , it is believed that more derived oviraptorosaurs like gigantoraptor also had feathers. Gigantoraptor could have lost the feathers secondarily, because they were no longer needed for thermal insulation due to the enormous size of the animal - analogous to today's hairless large mammals such as elephants . However, the researchers assume that Gigantoraptor showed at least the long arm feathers of its ancestors, as these were not used for thermal insulation: Based on the bird-like breeding position of some oviraptorids that were discovered including their nest, some researchers assume that the long arm feathers are used Incubation of the eggs were used. Still, the researchers note that additional evidence from the fossil record is essential to confirm the presence of feathers in gigantoraptors .
swell
Unless otherwise stated, all information comes from the following article:
- Xing Xu , Qingwei Tan, Jianmin Wang, Xijin Zhao , Lin Tan: A gigantic bird-like dinosaur from the Late Cretaceous of China. In: Nature . Vol. 447, No. 7146, 2007, pp. 844-847, doi : 10.1038 / nature05849 .
Individual evidence
- ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , p. 152, online .
- ↑ Guy Newey: Gigantic dinosaur looked like a chicken. In: ABC - News in Science. June 14, 2007, accessed July 30, 2014 .
- ↑ a b c d Xing Xu, Qingwei Tan, Jianmin Wang, Xijin Zhao, Lin Tan: A gigantic bird-like dinosaur from the Late Cretaceous of China. Supplementary information . In: Nature. Vol. 447, No. 7146, 2007, pp. 844-847, doi : 10.1038 / nature05849 , (PDF; 187.58 kB).
