page_title: Cynodont
section_title: Evolutionary history
hierarchical_section_title: Cynodont / Evolutionary history
caption_attribution_description: Thrinaxodon liorhinus, an early triassic cynodont of South Africa, pencil drawing, after skeletal by Kemp (1982)
context_page_description: The cynodonts are therapsids that first appeared in the Late Permian. Mammals are cynodonts, as are their extinct ancestors and close relatives. All other cynodont lines went extinct.
context_section_description: Together with the extinct gorgonopsians and the therocephalians, the cynodonts themselves are part of a group of therapsids called theriodonts.
  The oldest and the most basal cynodont yet found is Charassognathus (Late Permian). Other basal cynodonts were the procynosuchids, a family that includes Procynosuchus and Dvinia. Cynodonts were among the few groups of synapsids that survived the Permian–Triassic extinction event and had a slow recovery after the extinction.
  The most derived cynodonts are found within the clade Eucynodontia, which also contains the members of Mammalia. Representative genera of nonmammalian cynodonts include the large carnivorous cynognathids, the equally large herbivorous traversodonts, and the small mammal-like tritylodontids and ictidosaurs. The presence of respiratory turbinates suggests a rapid metabolism and possibly endothermy.
  During their evolution, the number of cynodont jaw bones reduced. This move towards a single bone for the mandible paved the way for other bones in the jaw, the articular and angular, to migrate to the cranium, where they function as parts of the mammalian hearing system.
  Cynodonts also developed a secondary palate in the roof of the mouth. This caused air flow from the nostrils to travel to a position in the back of the mouth instead of directly through it, allowing cynodonts to chew and breathe at the same time. This characteristic is present in all mammals.
caption: Thrinaxodon from the Early Triassic of South Africa
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