Oviraptorosauria

Skeleton of a Citipati

  • Asia
  • North America

The Oviraptorosauria (derived from the Latin ovis - "egg"; raptor - " Robbers" and ancient Greek σαῦρος ( sauros ) = lizard, reptile ) are a group of dinosaurs within the theropods.

There were bipedal running, small to medium-sized theropods, which varied in size from truthuhngroßen Caudipteryx up to 8 meters long gigantoraptor. The short and deep skull had an often toothless beak, indicating a plant or omnivorous diet. Some species also showed a striking skull crest. Oviraptorosauria had a very bird-like appearance and were probably closely related to the ancestors of today's birds - some researchers even speculate that it has actually acted to flightless birds that evolved from flightless ancestors. At least some basal (primitive ) genera were feathered.

Systematically Oviraptorosauria can be divided into primitive genera such as Caudipteryx and in the groups Oviraptoridae and Caenagnathidae. Within the theropods they be counted among the Maniraptora, the Therizinosauroidea be regarded as next of kin. Together with the Therizinosauroidea form the Oviraptorosauria the taxon Oviraptoriformes.

Features

Oviraptorosauria were characterized by a short snout and deep, shaped into a beak from pine. The jaws were toothless, but four teeth showed in the basal genera Avimimus, Caudipteryx, Protarchaeopteryx and Incisivosaurus in the premaxillary bone ( at the front end of the upper jaw ) and sometimes much smaller teeth in the lower and upper jaw. In Caudipteryx the tooth crowns were needle-like. Incisivosaurus showed a pronounced heterodonte dentition: For each of the first tooth was flattened on each side of the premaxillary bone to an incisor and extremely extended. The Zwischenkieferbein was short, but very deep and showed a notched cutting edge at the bottom. The jaw bones were probably surrounded by a beak made ​​of horn substance.

As with all theropod skull showed multiple cranial window. The Antorbitalfenster, a skull window in front of the eye sockets, was short and high. The Caenagnathide Chirostenotes showed a prolonged Antorbitalregion, which could mean that some Caenagnathiden have had a longer skull than Oviraptoriden. The nostrils were greatly extended and Oviraptoriden usually. They were dominant, usually aligned elliptical and nearly vertical. The eye socket ( orbit ) and the Mandibularfenster in the lower jaw were great. The Infra pace Ralf Rochester, a skull window behind the eye socket was square and about the size of the eye socket.

The skull bones were out at Caudipteryx strongly pneumatized ( had cavities ) in Incisivosaurus at least nasal bone, lacrimal bone and square leg were pneumatized. Unlike other theropods in the Oviraptorosauria the parietal bone was at least as long as the skull.

Some representatives of the Oviraptoride various skull bones formed a conspicuous, highly pneumatized skull crest, which was similar to today's cassowaries. Since a skull crest was detected only at large skulls, it is presumed that he similarly developed as cassowaries in the adult animals, while he was still lacking in young animals ( allometry ).

Fuselage skeleton and limbs

Almost complete spine are known by many Oviraptoriden. The neck was relatively long and showed 1-2 cervical vertebrae more than in other theropods. Since the tail was short, his neck was strong " S" -shaped curved to hold their heads upright as possible, so that the equilibrium could be maintained. In total there were probably 12 to 13 cervical vertebrae found - the neck more than twice as long as the skull was. In addition, there are 9 to 10 dorsal, 6-8 sacral ( Synsakrum ), and 22 to 32 caudal vertebrae, the tail was shorter than in most other theropods. In Nomingia, Similicaudipteryx Citipati and Conchoraptor the last two to four caudal vertebrae were fused into a pygostyle, a feature which is otherwise known only from birds. Probably the tails wore long, ranging tail feathers that were the display behavior or courtship placed or spread. The Oviraptoriden all showed vertebra to the last caudal vertebrae Pleurocoele were so hollowed out on the front. Another feature of many Oviraptorosauria were deep hypapophyses that ran on the front half of the vortex centers of two to three vertebrae at the junction between the neck and back. The vortex centers were pneumatized, so permeated with potentially air-filled chambers.

The paired clavicle in the shoulder region was fused as in modern birds to furcula ( wishbone ). The pelvic bones were not fused together, except for Avimimus. The arms made ​​from 40 to 65 percent of the length of the rear legs. The hand was three units and the second ray longest. The first finger was strong, while the third finger was thin and often reduced - at Caudipteryx it consisted of only two phalanges (phalanges ). The thigh bone ( femur) represented 30 percent of the rear leg, the shinbone ( tibia) was 15 to 20 percent longer than the femur. The foot made ​​from 30 to 35 percent of the length of the rear legs.

At Avimimus and Caenagnathiden a Arctometatarsus showed, that is, that the third metatarsal viewed from the front only in the lower part of the middle foot was visible as it was masked by the contacting the second and fourth metatarsal bones in the upper part. However, this characteristic is absent in the Oviraptoriden and Caudipteryx.

Paleoecology

Undoubted remains of Oviraptorosauria come so far only from the northern hemisphere from Asia and North America, although there are reports of possible fragmentary remnants Oviraptoriden also from the southern hemisphere. Representatives of the group have been detected in many different ecosystems. Most frequently the remains found in the Upper Cretaceous of Central Asia in rocks that indicate a very dry habitat with sand dunes. In North America fossil remains are rare and appear sporadically in sediments that were deposited in the Upper Cretaceous ( Campanian and Maastrichtian ) of rivers.

System

  • Oviraptorosauria Incisivosaurus
  • Protarchaeopteryx
  • Avimimidae Avimimus
  • Caudipteryx
  • Similicaudipteryx
  • Citipati
  • Ganzhousaurus
  • Nemegtomaia
  • Oviraptor
  • Rinchenia

Swell

  • Halszka Osmólska, Philip J. Currie, Rinchen bars Bold: Oviraptorosauria. In: David B. Weishampel, Peter Dodson, Halszka Osmólska (eds.): The Dinosauria. 2nd edition. University of California Press, Berkeley, 2004, ISBN 0-520-24209-2, pp. 165-183.
Barremian Mya (unit) Coelurosauria Genus Quadrate bone Digital Object Identifier
628273
de