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The division of living beings into systematics is a continuous subject of research. Different systematic classifications exist side by side and one after the other. The taxon treated here has become obsolete due to new research or is not part of the group systematics presented in the German-language Wikipedia.

Proterosuchus , live reconstruction

The thecodontia ("root teeth") are a group of extinct reptiles that developed from the late Permian to the end of the Triassic (approx. 255 to 200 million years ago ) as the first major radiation of the basal Archosauria . The group established by Richard Owen in 1859 included in the past all archosaurs that were not assigned to any of the derived archosaur groups dinosaurs (including birds ), pterosaurs or crocodiles .

Although they were long considered a systematic group, today they are considered what is known as a paraphyletic group , as they contain both basic representatives and common ancestors of the three derived groups. Accordingly, the term Thecodontia is no longer in use in paleontological systematics today.


Ornithosuchus , living reconstruction

The group owes its name to the way in which the teeth are fastened in the jaw , which is known as thecodont (Greek theke = container, odous , odontes = tooth). The teeth of the thecodont animals sat - similar to those of mammals - in a maxillary cavity ( tooth socket ) and were not directly fused with the jawbone (acrodont), as in fish and amphibians, but attached by fiber bundles of the periodontal membrane ( tooth periosteum ). Another feature of these animals was the suborbital window, a larger opening in the bone of the floor of the eye socket.

Most of the thecodontia were quadruped, but there were also some species that moved on two legs (biped). These included the Ornithosuchidae in particular .


Stagonolepis as a representative of the Aetosauria , life reconstruction

Among the basal groups of Archosauriformes that you imputing the Thecodontiern, among which also paraphyletic proterosuchidae that erythrosuchidae that Proterochampsidae that phytosaur (Parasuchia) and the most likely herbivorous aetosaur and ' Rauisuchia ' that Lagosuchidae and ornithosuchidae .

Although the representatives of these groups can be easily distinguished from one another, there is hardly any evidence of similarities between individual groups that could be used as evidence of a closer relationship. In addition, some of the groups are now viewed as paraphyletic. A relationship analysis and thus a corresponding cladogram of the basal radiation of the Archosauria is only possible to a limited extent.


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