Therocephalia

Therocephalia Temporal range: Middle Permian to Early Triassic
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Synapsida
Order:	Therapsida
(unranked)	Theriodontia
Suborder:	Therocephalia Broom, 1905
Families
See "Taxonomy"

The Therocephalia ("Beast Head"), are a lineage of therapsids, specifically, they belong to a group called theriodontia, a group that includes gorgonopsians, and the cynodonts - which are the ancestors of mammals. They are at least as ancient as the Gorgonopsians, which they resemble, and in fact outlasted, making it through to the Early Triassic period. The Therocephalia's closest relatives were the cynodonts. Like Gorgonopsian and Cynodonts (not all cynodonts were carnivores), the Therocephalia were carnivores. The therocephalians may have shown endothermy. The earlier therocephalians were in many respects as primitive as the gorgonopsians, but they did show certain advances such as the enlargement of the temporal opening, for a lighter skull and more efficent muscle attachment, and reduction of the phalanges - finger and toe bones to the mammalian formula. The later therocephalians included the advanced bauriamorphs, which carried some theriodont characters to a high degree of specialization. For instance, in Bauria there was no bar of bone separating the orbit from the temporal opening; a condition typical for primitive mammals. These and other advanced features led to the long-held opinion, now rejected, that the Ictidosaurs and even some early mammals arose from a bauriamorph stem. The situation seems to be that mammalian characteristics evolved in parallel among a number of different groups. It is not surprising that several therocephalian groups, like the Lycosuchidae and the Scaleposauridae, have turned out to be artificial, the former based on skulls which retain an extra set of canines, and the latter based on mostly juvenile charcteristics. The therocephalians were almost extinguished by the Permian-Triassic extinction, but they survived and making it through the Early Triassic Period. However, the last therocephalians did not make it through the Middle Triassic Period, and are extinct by that time. They were probably outcompeted by cynodonts, such as Cynognathus - which is the undisputed predator of the Early Triassic epoch and the evolving archosaurs, which later dominated the land for the rest of the Mesozoic Era, as dinosaurs.

Taxonomy

• Order Therapsida
• Suborder Therocephalia
  • Family Nanictodopsidae
  • Family Crapartinellidae
  • Family Simorhinellidae
  • Family Lycidopsidae
  • Family Ericolacertidae
    • Ericiolacerta
  • Family Pristerosauria
  • Family Scaleposauridae
    • Family Scylacosauridae
  • Infraorder Eutherocephalia
    • Family Moschorhinidae
      • Subfamily Annatherapsinae
      • Subfamily Euchambersiinae
      • Subfamily Moschorhininae
    • Family Whaitsiidae
    • Superfamily Baurioidea
      • Family Ictidosuchopsidae
      • Family Bauriidae
        • Subfamily Nothogomphodontinae
        • Subfamily Bauriinae
  • Family Lycosuchidae