Palatal teeth

Occurrence

Palatal teeth are both present in Actinopterygii (ray-finned fish) and Sarcopterygii, and were inherited as an ancestral trait by the last common tetrapod ancestor. Palatal dentition is widespread amongst early tetrapods, though in many lineages of Amniota the palatal dentition became reduced and in some cases entirely lost, the latter including cynodonts (the ancestor of mammals), the ancestors of living turtles (though it is retained in very early stem turtles like Proganochelys), as well as the vast majority of archosaurs (which includes crocodilians, dinosaurs and their bird descendants), though a handful of archosaurs are known to retain a pterygoid tooth row, including the primitive dinosaurs Eodromaeus and Eoraptor, and the primitive pterosaur Eudimorphodon. Loss was not entirely uniform, and some lineages appear to have regained regions of palatal teeth that had been previously ancestrally lost. Lepidosaurian reptiles, including squamates (lizards and snakes) and the tuatara as well as living lissamphibians retain palatal teeth. Some lizard groups have lost palatal teeth, including geckoes, agamids and chameleons. Numerous lineages of frogs have also lost palatal teeth (often alongside the marginal teeth), while they are retained in all salamanders and caecilians.