. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. THE DENTITION OF THE TITAN OSU CHI AN DINOCEPHALIANS IO5 both are not functioning at the same time either the anterior or the posterior one assumes the function of both. This is the stage reached by the Sphenaco- dontia. The next stage is one to be postulated for the ancestral therapsid or pro-therapsid. Here the dentition would consist of about 7 upper incisors, a pair of canines, which are the first two teeth on the maxilla, numerous post- canines; one incisor less in the dentary, a single lower ca
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. THE DENTITION OF THE TITAN OSU CHI AN DINOCEPHALIANS IO5 both are not functioning at the same time either the anterior or the posterior one assumes the function of both. This is the stage reached by the Sphenaco- dontia. The next stage is one to be postulated for the ancestral therapsid or pro-therapsid. Here the dentition would consist of about 7 upper incisors, a pair of canines, which are the first two teeth on the maxilla, numerous post- canines; one incisor less in the dentary, a single lower canine and a long row of postcanines. All the teeth would be simple conical teeth, with probably serrated edges in the incisors and canines. From some such pro-therapsid stage the various primitive therapsid sub-orders diverged. One of these branches represents the sub-order Dino- cephalia. In the ancestral dinocephalian the dentition must have been as follows: 5 upper and 4 lower incisors, a single upper and lower canine and numerous postcanines. All the teeth were still simple conical structures with or without serrated edges. Each functioning tooth was replaced by a tooth arising lingually to it. In occlusion all the teeth of the upper jaw passed labially of the teeth of the lower jaw and the dentition was definitely of a habit usually inter- preted as being 'carnivorous'. In the next stage, this carnivorous dentition with upper teeth occluding labially of the lower teeth, changed to a carnivorous dentition in which the incisor teeth commenced to intermesh with each other. This development of intermeshing incisors was a step which definitely split the Dinocephalia off from the other Therapsida and set them off on their own separate course, and it is the possession of this distinctive character that we consider to be a major justification of our considering the Dinocephalia to constitute a distinct sub-order. Although continuing to retain this common character the Dinocephalia
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
