Cynodont

Skull of the genus Cynognathus

  • Worldwide

The Cynodontia (literally " Hundezähner " ) are the group of Therapsida (formerly "mammal like reptiles " called ) with the greatest biodiversity. Today they are represented by the mammals, all other sub- groups already died from the Mesozoic.

The first published Cynodontia million years ago during the Permian about 270. Fossils from this time have been found in South Africa, Zambia, Russia and Western Europe. The animals survived the mass extinction at the end of the Permian and experienced a rapid adaptive radiation in the Triassic, a development that culminated in the emergence of mammals. Those Cynodontia who were not mammals, probably survived until the Cretaceous, but at least until the Middle Jurassic.

Features

The Cynodontia share a number of characteristics with the Therocephalia, with whom they form the taxon Eutheriodontia. Their monophyly is well established by a total of 27 synapomorphies, most of the skull on. Their skulls are similar to those of mammals, the temporal region is wide, the zygomatic arch invites far out, the muzzle is usually low. Apart from Procynosuchus and his relatives, found on all Cynodontia a secondary palate, which separates the respiratory and Nahrungsweg each other. Palate window does not exist. The wing leg does not reach behind the square leg. The square cheekbone that is absent in mammals, and the square leg, which has become in mammals to the anvil, one of the ossicles are greatly reduced. At the large, plate-like mind gradually develop the two head joints of mammals.

In the lower jaw, the dentary by far the largest bones. The bone behind be regressed. In the mandible, followed by the canines 7-13 molars, which are wide and provided with numerous bumps. The molars are partially partitioned into premolars and molars.

Complete skeletons were found only a few, probably was the tail usually short. There are always four sacral vertebrae. The limbs, shoulder and pelvic girdles are similar to mammals, the number of phalanges, similar to the reptiles, still high ( Phalangenformel 2,3,4,4,3 ).

System

  • Cynodontia Procynosuchus
  • Dvinia
  • Epicynodontia Galesauridae Cynosaurus
  • Galesaurus
Mya (unit) Richard Owen Incus Thrinaxodon
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