Theriodontia


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Related to Theriodontia: Pelycosauria, Enterozoa

Theriodontia

 

a suborder of extinct reptiles of the subclass Theromorpha. They existed from the late Permian to the middle Jurassic period and were the ancestors of mammals.

Theriodontia had a number of features common to mammals: clearly differentiated teeth (incisors, canine teeth, and molars), a secondary palate, a somewhat shortened facial part of the skull, disappearance of the postorbital temporal arc and the rear bones of the lower jaw, the appearance of a bifurcated occipital condyle, loss of the parietal opening, differentiation of the lumbar division of the spine, and a more advanced (vertical) orientation of the extremities. The most advanced group of Theriodontia were the ictidosaurs, the possible direct ancestors of mammals, or very close to the ancestors. The following superfamilies also belong to Theriodontia: Gorgonopsis (Inostrancevia), Cynodontia (Dvinia, Cynognatia), Tritylodontia, Therocephala, and Bauriamorphi. The remains of Theriodontia are most numerous in southern Africa and the European part of the USSR.

REFERENCES

V’iushkov, B. P. “Terotsefaly Sovetskogo Soiuza.” Tr. Paleontologicheskogo in-ta AN SSSR, 1955, vol. 49.
Osnovy paleontologii, vol. 12: Zemnovodnye, presmykaiushchiesia iptitsy. Moscow, 1964.

A. K. ROZHDESTVENSKII