Thecodontia

The Thecodontia ( " Wurzelzähner " ) are a group of extinct reptiles that have evolved ( million years ago, about 255 to 200) as the first major radiation of basal Archosauria from the Late Permian to the end of the Triassic. The by Richard Owen in 1859 established group included in the past all archosaurs, which (including birds), pterosaurs and crocodiles were not associated with any of the derived Archosauriergruppen dinosaurs.

Although they were long regarded as a systematic group, they are now seen as so-called paraphyletic group because they contain both basal representatives as well as a common ancestor of the three groups derived. Accordingly, the designation Thecodontia in the paleontological systematics is no longer in use today.

Features

Owes its name to the group of the type of attachment of the teeth in the jaw, as thecodont (Greek counter = container, Odous, odontes = tooth) is called. The teeth of the Thecodontier sat - similar to mammals - in a Kieferhöhlung ( tooth socket ), and were not attached directly to the jaw bone ( akrodont ), as in fish and amphibians, but by fiber bundles of the periodontal ligament ( Zahnperiost ) attached. Another feature of these animals was the Suborbitalfenster, a larger opening in the bone of the floor of the orbit.

The Thecodontia were mostly fours, but there were among them some species that were moving on two legs ( biped ). These included mainly the Ornithosuchidae.

System

Among the basal groups of Archosauriformes that you imputing the Thecodontiern, also included the paraphyletic Proterosuchidae that Erythrosuchidae that Proterochampsidae that Phytosauria ( Parasuchia ) and the most likely herbivorous Aetosauria and the ' Rauisuchia ', the Lagosuchidae and Ornithosuchidae.

Although the members of these groups can distinguish each other very easily, there is little evidence on similarities individual groups, which could be used as evidence for a closer relationship. In addition, some of the groups are now regarded as paraphyletic. A kinship analysis and thus a corresponding cladogram of basal radiation of the Archosauria is correspondingly limited.