Detailed comparisons of the dentitions of extant hexanchid sharks and Tertiary hexanchid teeth from South Australia and Victoria, Australia

Abstract

In extant hexanchid sharks except for (usually) a bigger primary cusp, isolated teeth of a given size of the smaller species Hexanchus vitulus (Springer and Waller) may be confused with those of H. griseus (Bonnaterre). This specific size difference has significance in the fossil record. Heptranchias perlo (Bonn.) differs in its more slender and relatively larger primary cusp with basal denticles (not serrations as in Hexanchus) on its mesial margin and fewer crownlets increasing and then decreasing in size distally. Notorynchus cepedianus (Peron) differs mainly in its more robust primary cusp and crownlets which are fewer in number than in Hexanchus and which decrease evenly in size distally, like Hexanchus. Cali-fornian specimens of Notorynchus are included in the monotypic TV. cepedianus until the taxonomic significance of the variability of the upper medial teeth is established and defined.