Distribution and diversity patterns of Triassic cynodonts (Therapsida, Cynodontia) in Gondwana

Cynodonts are an important component of Triassic tetrapod faunas and are frequently one of the dominant groups. A summary of their record during the Triassic of Gondwana is presented. Cynodonts are represented by 63 species/57 genera in Gondwana with diversification peaks occurring during the Late Anisian (particularly in Africa) and the Carnian of South America and India. Data on the number of faunas of each age and the duration (in millions of years) estimated for these faunas were integrated with cynodont generic diversity values. One of the most important turnovers in cynodonts occurred at the Late Olenekian–Anisian, involving changes in two directions: a) the record of complex bucco-lingually expanded (gomphodont) postcanines, with traversodontid cynodonts already representing an important group at the end of the Anisian; b) the record, particularly during the Anisian, of significantly large-sized cynodonts (e.g. Cynognathus and Diademodon with basal skull length between 30 to 40 cm). Considering that the global maximum peak of cynodont diversity is during the Norian–Rhaetian, the diversity of Gondwanan cynodonts for that time, eight taxa, is remarkably low.