Delphinoidea Gray, 1821

Fitzgerald, Erich M. G., 2005, Pliocene marine mammals from the Whalers Bluff Formation of Portland, Victoria, Australia, Memoirs of Museum Victoria 62 (1), pp. 67-89 : 75

Superfamily Delphinoidea Gray, 1821

Incertae sedis

Referred specimens. NMV P218283, P218284 and P218286, all isolated teeth (not figured).

Description. P21283, P218284 and P218286 all represent small odontocete teeth possessing conical enamel-covered crowns that bear fine wrinkling ornamentation, and curve lingually towards the crown apex. As in kentriodontids, there is a lingual bulge at the base of the crown but this feature is not as prominent in the teeth from Portland. None possesses an open pulp cavity suggesting that all were derived from adult individuals.

P218283 is an incomplete tooth, its preserved maximum length and maximum width of the crown being 16 mm and 6 mm respectively. Due to the incomplete nature of this tooth it does not warrant further description.

P218284 is the most highly polished and the most complete. It differs from the others in having a mediolaterally compressed root with a more prominent mesial-distal bulge at its midpoint. The preserved apex of the root curves posteriorly.

The most notable feature of P218286 distinguishing it from the other teeth is its bulbous root, which contrasts with the transversely flattened morphology of P218284.

Discussion. Only one delphinoid odontocete has previously been described from the Tertiary of Australia, the latest Miocene-earliest Pliocene “ Steno ” cudmorei Chapman (1917) from the Black Rock Sandstone of Beaumaris, Victoria ( Fitzgerald, 2004b). Fordyce (1982) questioned the taxonomic identity of “ S.” cudmorei (the holotype, P13033, being an isolated tooth) and Fitzgerald (2004b) referred “ S.” cudmorei to Delphinidae , genus and species indeterminate. Chapman (1917) assigned P13033 to Steno on the basis of the resemblance of its crown ornamentation to that seen in the teeth of the extant Steno bredanensis Cuvier in Lesson, 1828 (e.g., Miyazaki and Perrin, 1994). Given that Steno is probably in a basal position in the phylogeny of Delphinidae ( Miyazaki and Perrin, 1994; LeDuc et al., 1999) and that some of the presumed ancestors of Delphinidae , the Kentriodontidae ( Barnes, 1978, 2002; LeDuc, 2002), possessed Steno-like crown ornamentation (e.g., Kellogg, 1966), the anastomosing striae on the crown of P13033 (and P218283, P218284, P218286) are of dubious use in assessing the phylogenetic affinities of isolated teeth. Furthermore, non-delphinid small odontocetes such as Lipotes vexillifer Miller, 1918 possess anastomosing wrinkling on tooth crown enamel ( Miller, 1918; Brownell and Herald, 1972; Barnes, 1985) which casts doubt on any perceived taxonomic or phylogenetic signal present in these teeth.

The isolated teeth from Portland are assigned to Delphinoidea incertae sedis. None of the Portland Pliocene teeth share demonstrably close affinities with the holotype tooth of “ Steno ” cudmorei.