IV - On the tooth-replacement in theriodont reptiles

Abstract

In describing the very mammal-like dentitions of some of the advanced Theriodont reptiles various authors have identified premolars and molars (Broom , 1913). Though there is some evidence for this differentiation in the form of the teeth of some of the gomphodont cynodonts, there is no satisfactory evidence that only two dentitions were present or that the replacement was of a mammalian type. On the other hand Sushkin (1927) described the type of the primitive cynodont Permocynodon sushkini , Smith Woodward , as having several molariform teeth “ changing ” and says “ it may be established thus that the teeth are changing irregularly as usually in the reptiles and that there is no difference in this respect between the anterior and hindermost teeth ; thus despite the difference of the form, no premolars and molars can be distinguished” . Unfortunately he does not say which teeth are changing. Other authors, uncertain of the manner of replacement, have avoided implying a mammalian succession by the use of such terms as “ cheek ” teeth or “ post-canine” teeth.