Tritheledontidae
- South Africa
- North America
- Brazil ( Caturrita Formation)
- Württemberg ( Halberstadt )
The Trithelodonta, also called Ictidosauria ( Wiesel lizards ) are terrestrial vertebrates from the group of therapsids ( " mammal -like reptiles "). They include mainly small insectivorous forms. In addition to the Tritylodontidae they are the group that had most similarity with mammals.
Features
The Trithelodonta were rather small, but well known are their only three to six inches long skull. The postcranial skeletons has been preserved only in a few fossil fragments. Humerus and femur of Pachygenelus are those of the basal mammal Morganucodon very similar.
Of the skull bones they had lost the Präfontale and Postorbiltale and therefore the orbits were not separated from the skull windows. Her skull window was, in contrast to the Tritylodontidae, elongated, the sagittal crest broad and low. The Trithelodonta had a double jaw joint, the more modern secondary TMJ Dental and squamosal from the front, the old reptilian from articular quadrate from the back.
The main feature for determining the Trithelodonta is the specialized dentition in which they can be distinguished by the Tritylodontidae. In Pachygenelus only two incisors are present in the upper and lower jaw. The canines are similar to those of the other Cynodonten.
System
Kuhn held the Trithelodonta nor descendants of Bauriamorpha. Today, however, they are, as well as the Tritylodontidae, as derived Cynodonten.
Genera
- Brasilodon
- Brasilitherium
- Chaliminia
- Diarthrognathus
- Pachygenelus
- Prozostrodon
- Riograndia
- Therioherpeton