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. Californian 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. N. cepedianus is recorded from the fossil record for the first time. Heptranchias haswelli Ogilby is regarded as a species inquirenda. Hexanchus agassizi Cappetta is expanded to include the Eocene Hexanchus teeth from South Australia. Heptranchias howellii (Reed) from the South Australian Eocene and Notorynchus primigcnius (Agassiz) from the Victorian Miocene are recorded and described from Australia for the first time. Recently Bass et al. (1975) suggest that more detailed anatomical studies of the six-and sevengill sharks may show that the smaller species of Hexanchus, H. vitulus, may have more in common with Heptranchias perlo than with the larger species, Hexanchus griseus. H. griseus, on the other hand, may have more in common with Notorynchus cepedianus. Until these suggestions are confirmed or repudiated by further detailed work the suprageneric classification adopted here is that of Patterson (1967). Terminology The tooth types medials, laterals and posteriors are used in the sense of Applegate (1965a). The faces of a tooth are termed labial and lingual and the margins mesial and 61

Comments on hexanchiform phylogeny (Pisces, Neoselachii)

“…First, +"H." rucilis possesses well developed and strongly calcified vertebral centra throughout the entire lengti of the vertebral column whereas these are absent precaudall in the modern Hexunchus (CAPPETI-A 1980; REMANE 1936; Table). Second, the lower symphysearteeth of + "H." gra~ilis lack a median principal cusp whereas such a cusp is present in the lower symphyseals of both living Hexuncbus species (CAPPETTA 1980;KEMP 1978). For these reasons I do not regard the fossil +"H." grucilis as being congeneric with the Recent Hexuncbus but as representing a new genus.…”

A review of the Tertiary fossil Cetacea (Mammalia) localities in Australia

“…Terrestrial and freshwater vertebrate faunas were adopted from Rich and others (1991), and unpublished data provided by K. Piper. Chondrichthyan and osteichthyan faunas were adapted from information in Kemp (1978, Pledge (1985) and Stinton (1958Stinton ( , 1963 as well as my own observations. Although Pledge (1967) reviewed South Australian Tertiary chondrichthyans, his published localities for chondrichthyans cannot be correlated with South Australian cetacean localities.…”

A new Jurassic cow shark (Chondrichthyes, Hexanchiformes) with comments on Jurassic hexanchiform systematics

“…The dental terminology used herein follows that of Applegate (1965) and Kemp (1978). The taxonomic scheme adopted here is based on Kriwet and Klug (2004), Cappetta (2006) and Cione and Medina (2009 …”