An order of Reptilia, subclass Synapsida, often called advanced mammallike reptiles, that flourished from the middle Permian through the Late Triassic. The group is highly diverse and subdivided into six suborders. Two of these, Eotitanosuchia and Dinocephalia, include relatively primitive mid-Permian carnivores and herbivores. A third, the Dicynodontia, made up of small to large herbivores, was abundant in the late Permian. Dicynodonts were associated with two carnivorous suborders, the Therocephalia and Gorgonopsia, which are morphologically intermediate between Eotitanosuchia and the cynodonts. Although these five developing lines are distinct, the skulls and skeletons in each became increasingly mammallike.