Tyrannosauridae
| Tyrannosauridae | ||||||||||||
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Skeleton reconstruction of an individual from Tyrannosaurus rex (nickname "Stan") in the Manchester Museum |
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous (middle Campanium to Maastrichtian ) | ||||||||||||
| 80.6 to 66 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Tyrannosauridae | ||||||||||||
| Osborn , 1906 | ||||||||||||
The Tyrannosauridae (Tyrannosauruses i. E. P) are a family from the lizard dinosaurs -Großgruppe the Theropoden that previously only from the higher Cretaceous North America and Asia is known. It includes some of the largest known carnivorous creatures.
The very small arms with only two fingers per hand are typical of this family. Apart from this peculiarity, the physique of the tyrannosaurids shows numerous parallels to other relatively large carnivorous archosaurs of the Mesozoic Era ( ornithosuchids , carnosaurs , abelisauroids ): large skull, massive torso and powerful tail.
External systematics, fossil record and evolution
The Tyrannosauridae are a group of the “more modern” theropods ( Avetheropoda ) and belong within this group to the more “modern” line of the coelurosaurs , the sister group of the Carnosauria. * The Coelurosauria in turn split up into the Maniraptoriformes , which include many rather small and gracefully built representatives, and the Tyrannosauroidea (tyrannosaurs i. W. S.) with rather large, massively built representatives. The apparently close relationship between tyrannosauroids and Maniraptoriformes means that, contrary to what was assumed in the 1980s, the tyrannosaurs are not descendants of large Jurassic theropods such as Eustreptospondylus or Allosaurus , but must have evolved from graceful forms such as Compsognathus . The similarity with representatives like Allosaurus is therefore the result of a convergent development. The Tyrannosauridae are the most strongly derived ("most modern") representatives of the Tyrannosauroidea.
While the first tyrannosauroids appear in the Upper Jurassic and are known from North America and Asia (especially China) also from Europe (e.g. Aviatyrannis jurassica from Portugal or Eotyrannus lengi from England), the geographical and stratigraphic distribution of the Tyrannosauridae is in the Upper Cretaceous North America and Asia (Mongolia). Its oldest representative is Lythronax from the central Campan of North America. In addition, the early tyrannosauroids are still relatively small with a length of 2 to 6 meters, had a less pronounced high snout, ¶ were probably very agile and still had three finger rays per hand.
Because primitive plumage has been demonstrated in two Chinese genera of the Tyrannosauroidea ( Dilong and Yutyrannus ), it is speculated whether the body of the Tyrannosauridae, for which such evidence has so far been lacking, was also covered with proto-feathers. In some cases, tyrannosaurids are even shown with contour feathers in living reconstructions . However, there is evidence that the plumage in this group was reduced secondarily.
Internal systematics and characteristics
The Tyrannosauridae were defined node-based in 2010 as the last common ancestor of Tyrannosaurus rex , Albertosaurus sarcophagus and Gorgosaurus libratus and all of their descendants. Which special common anatomical features make up the Tyrannosauridae can therefore vary to a certain extent, depending on the result of a relationship analysis.
Generally typical characteristics of the tyrannosaurids are their large to gigantic stature, the generally large skull (almost half as long as the cervical and trunk spine combined), whose broader, box-like rear (postrostral) part is more or less clearly separated from the snout (rostrum) , with eye sockets facing forward to some extent. The bone struts that frame the temporal window are thickened and have lateral outgrowths that protrude into the window. The snout is high and U-shaped when viewed from the mouth. The skull was probably only weakly or not at all mobile . The back of the muzzle and the anterior region above the eye show evidence of the presence of low or short horn-like structures. The lower jaw is very robust and comparatively high, especially in the rear (post-dental) area. The cervical spine is rather short and the vertebrae are stocky. The tyrannosaurids differ from all other similar theropods in their severely stunted forelimbs, which end in only two finger rays. The metacarpal of the third finger beam is rudimentary in the form of a bone splint, but more or less fused with the metacarpal of the second finger beam. Another distinguishing feature is the arctometatarsus , a special form of the formation of the metatarsal in which the third metatarsal tapers significantly in the direction of the tarsus.
The structure of the skull, lower jaw and cervical spine shows that the tyrannosaurids were likely to have had a great deal of jaw and neck muscle mass and thus a high bite and speed force. The shortened neck was necessary to be able to carry the heavy head. The more forward-facing eye sockets suggest a certain ability to see three-dimensionally . The function of the "little arms" is unclear. Possibly they helped the males hold onto the female during copulation .
The different genera are morphologically very similar. They differ in their body size, among other things: While Alioramus ** was five to six meters long, Albertosaurus , Daspletosaurus and Gorgosaurus reached a length between eight and ten meters. Tarbosaurus and Tyrannosaurus even came to body lengths of around 12 m and were thus among the largest predatory dinosaurs. The most strongly derived, including the largest, Tyrannosauridae are grouped together in the subfamily Tyrannosaurinae . This is a sister group of the clade from Albertosaurus and Gorgosaurus, which is sometimes endured as the subfamily Albertosaurinae. The cladogram below shows a current hypothesis of the relationships between the Tyrannosauridae (after Loewen et al., 2013):
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Not included in the cladogram are the genera Nanuqsaurus (Alaska), which was only described in 2014 and whose first publication found a sister group relationship to Tarbosaurus + Tyrannosaurus , and Qianzhousaurus (China), which is said to be related to Alioramus .
Remarks
- *In the traditional, pre-cladistic system, all large, massively built theropods are summarized in the Carnosauria group and contrasted with the graceful, lighter built Coelurosauria. This system is considered to be out of date since cladistic analyzes revealed that many of these "carnosaurs" are more closely related to "coelurosaurs" than to other "carnosaurs". The tyrannosaurids are now grouped with the newly defined clade Coelurosauria, because they are more closely related to genera such as Deinonychus or Ornithomimus than to genera such as Allosaurus or Ceratosaurus .
- **The position of Alioramus is not entirely clear. In various analyzes based on different data sets, it appears either as a basic representative of the Tyrannosaurinae or as a "more modern" Tyrannosauroide, still outside the Tyrannosauridae.
- ¶In the palaeontological literature, the expression shallow-snouted ('flat -snouted ') is used for this, but a “flat -snouted ” tyrannosauroid has compared with theropod genera such. B. Baryonyx or Spinosaurus still have a very high snout.
Web links
- Thomas R. Holtz, Jr .: Tyrannosauridae. Tyrant dinosaurs. August 29, 2000 version, Tree of Life Web Project
- Tyrannosauridae on Palaeos.com
Individual evidence
- ↑ a b c Complete paragraph, with the exception of otherwise marked passages, from Gregory S. Paul: The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , pp. 102-110, online .
- ↑ z. B. Robert L. Carroll: Vertebrate Paleontology and Evolution. WH Freeman & Co., New York 1988, ISBN 0-7167-1822-7 , p. 297.
- ↑ a b c d Mark A. Loewen, Randall B. Irmis, Joseph JW Sertich, Philip J. Currie, Scott D. Sampson: Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans. In: PLoS ONE . Volume 8, No. 11, 2013, e79420, doi: 10.1371 / journal.pone.0079420 .
- ^ Brian Switek: The truth about T. rex. In: Nature News Feature. October 23, 2013.
- ^ A b c Anthony R. Fiorillo, Ronald S. Tykoski: A Diminutive New Tyrannosaur from the Top of the World. In: PLoS ONE. Vol. 9, No. 3, 2014, e91287, doi: 10.1371 / journal.pone.0091287
- ↑ a b Kenneth Carpenter: Tyrannosauridae. In: Philip J. Currie, Kevin Padian: Encyclopedia of Dinosaurs. Academic Press, San Diego et al. a. 1997, ISBN 0-12-226810-5 , pp. 766-768.
- ↑ a b Thomas D. Carr, Thomas E. Williamson: Bistahieversor sealeyi , gen. Et sp. nov., a new tyrannosauroid from New Mexico and the origin of deep snouts in Tyrannosauroidea. In: Journal of Vertebrate Paleontology. Vol. 30, No. 1, 2010, pp. 1–16, ISSN 0272-4634 , doi: 10.1080 / 02724630903413032 (alternative full text access : ResearchGate )
- ↑ Junchang Lü, Laiping Yi, Stephen L. Brusatte, Ling Yang, Hua Li, Liu Chen: A new clade of Asian Late Cretaceous long-snouted tyrannosaurids. In: Nature Communications. 5, item no. 3788, 2014, ISSN 2041-1723 , doi: 10.1038 / ncomms4788 .
- ↑ Thomas D. Carr, Thomas E. Williamson, Brooks B. Britt, Ken Stadtman: Evidence for high taxonomic and morphologic tyrannosauroid diversity in the Late Cretaceous (Late Campanian) of the American Southwest and a new short-skulled tyrannosaurid from the Kaiparowits formation of Utah. In: Natural Sciences . Volume 98, No. 3, 2011, pp. 241-246, doi: 10.1007 / s00114-011-0762-7