Paraves
| Paraves | ||||||||||||
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House Sparrow ( Passer domesticus ), a recent representative of the Paraves |
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| Temporal occurrence | ||||||||||||
| Middle Jurassic ( Bathonium ) until today | ||||||||||||
| 167.7 to 0 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Paraves | ||||||||||||
| Sereno , 1997 |
The paraves is one of Paul Sereno defined in 1997 taxon of theropod . Sereno defined them as all maniraptors more closely related to the recent birds (Neornithes) than to Oviraptor .
features
limbs
Like all terrestrial vertebrates (Tetrapoda) , the Paraves have two pairs of extremities , the front legs (hands) are wings in birds and arms in the Deinonychosauria . The paraves are or were biped , so their movement took place exclusively with the hind legs. They each have three toes. They ended in sharp claws made of horn that sat on pointed, curved bone cones. A peculiarity developed within the Deinonychosauria. Here the second toe was equipped with a particularly large and sharp claw and also had a special joint. This made it possible to lift the toe when moving (functional didactyly) in order to avoid wear and tear, and a high degree of mobility when hunting. The bipedal and three-toed ornithopods from the group of bird's pelvis dinosaurs lack long claws, which is important for the assignment of fossil footprints .
pool
In the construction of the pelvis , as with all pelvic dinosaurs (Saurischia), the pubic bone (Os pubis) originally protruded forwards. In the course of the development of the theropods there has been a rotation, with the Deinonychosauria it points downwards and with the birds it finally points backwards. The basin of today's birds is confusingly similar to that of the bird basin dinosaur , the second subgroup of dinosaurs. Nevertheless, birds evolved from lizard pelvis and not from bird pelvic dinosaurs, the similarity is only superficial.
feathers
Feathers are also an important feature . The first direct evidence of feathers in dromaeosaurids came in 1999 with the description of Sinornithosaurus . This skeleton shows areas with structures approximately four centimeters long on different parts of the body, but the anatomy of which is not recognizable. Various other feathered dromaeosaurids have been discovered since this discovery. The type specimen of Microraptor zahoianus described in 2000 shows imprints, which presumably come from feather shafts (rachis), which suggests real contour feathers. Another fossil described in 2001, possibly belonging to Sinornithosaurus , shows feathers on all parts of the body except the lower portion of the legs. Other Microraptor fossils , in particular the Microraptor gui finds , suggest arm and leg wings that were constructed similar to the wings of today's birds. Some of these flight feathers have asymmetrical spring flags, which suggests an aerodynamic function. Some wing feathers could be more than twice as long as the femur. In birds, the plumage largely determines the overall appearance: the body is covered by feathers . When flying, these structures made of keratin serve as a wing and control surface, an aerodynamically favorable cladding of the body and as insulation , which can even be changed, mostly depending on the temperature and wind. The plumage is also colored and is often used for sexual advertising. In water birds it is water-repellent and provides buoyancy. The plumage is changed at certain times ( moulting ). Furthermore, the legs of all birds are covered by skin flakes.
Taxonomy and systematics
Taxonomy
The paraves are paraphyletic , which means that the paraves have common ancestors, but do not contain all subgroups, since the birds are counted as a separate class and the remaining paraves are counted as dinosaurs , i.e. reptiles .
External system
The paraves are a theropod taxon . Within the theropods they belong to the Tetanurae . The following cladogram illustrates the relationships:
| Theropoda |
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Internal system
The internal system of the paraves is controversial. Some paleontologists include the Alvarezsauridae and call the remaining taxa Eumaniraptora , while others, such as F. Zhang, exclude the Alvarezsauridae. Cladogram according to Zhang et al. from 2008:
| Paraves |
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Another possible cladogram according to Weishampel, Dodson and Osmólska:
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Individual evidence
- ^ Paul C. Sereno : The origin and evolution of dinosaurs. In: Annual Review of Earth and Planetary Sciences. Vol. 25, 1997, ISSN 0084-6597 , pp. 435-489, doi : 10.1146 / annurev.earth.25.1.435 .
- ^ Paul C. Sereno: A rationale for phylogenetic definitions, with application to the higher level taxonomy of Dinosauria. In: New Yearbook for Geology and Paleontology. Treatises. Vol. 210, 1998, ISSN 0077-7749 , pp. 41-83.
- ↑ Einhard Bezzel , Roland Prinzinger : Ornithology. 2nd, completely revised and enlarged edition. Eugen Ulmer, Stuttgart 1990, ISBN 3-8001-2597-8 .
- ↑ a b c d e 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 .
- ↑ 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 .
- ↑ 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 .
- ↑ Ji Qiang, 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 .
- ↑ 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 .
- ↑ Fucheng Zhang, Zhonghe Zhou, Xing Xu, Xiaolin Wang, Corwin Sullivan: A bizarre Jurassic maniraptoran from China with elongate ribbon-like feathers. In: Nature. Vol. 455, No. 7216, 2008, pp. 1105-1108, doi : 10.1038 / nature07447 .