A saber-tooth is any member of various extinct groups of predatory therapsids, predominantly carnivoran mammals, that are characterized by long, curved saber-shaped canine teeth which protruded from the mouth when closed. Saber-toothed mammals have been found almost worldwide from the Eocene epoch to the end of the Pleistocene epoch.
From top and from left to right, Inostrancevia, Hoplophoneus, Barbourofelis, Smilodon, Machaeroides and Thylacosmilus
1st saber-tooth instance: Gorgonopsidae (Theriodontia, Therapsida, Synapsida) – Lycaenops angusticeps skull
3rd saber-tooth instance: Thylacosmilidae (Sparassodonta) – Thylacosmilus atrox skull
4th saber-tooth instance: Oxyaenidae (Creodonta) – Machaeroides skull
Therapsida is a clade composing of a major group of eupelycosaurian synapsids that includes mammals and their ancestors and close relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more underneath the body, as opposed to the sprawling posture of many reptiles and salamanders.
Therapsida
Illustration of Alopecognathus, an early therocephalian therapsid
Holotype skull of Raranimus dashankouensis, the most basal known therapsid
Restoration of Euchambersia with dicynodont prey. Note that this South African therocephalian is suspected to be the oldest known venomous tetrapod.
