Fossil dolphins (Odontoceti) from Otekaike limestone (Duntroonian to Waitakian stages) near Tokarahi, North Otago, New Zealand

Samson, Catherine R. (Catherine Ruth), 1970-

Two new species of fossil dolphin from the Otekaike Limestone, near Tokarahi, North Otago, New Zealand, expand the record of early platanistoids. Both species are included within Platanistoidea (Cetacea: Odontoceti) on the basis of the following features: a highly vascularised fossa dorsal to the inner apex of the external auditory meatus; a dorsally concave anteroexternal sulcus on the dorsal surface of the periotic; a supratubercular groove on the dorsal surface of the periotic; and a longitudinal ventral groove in the tympanic bulla. The first dolphin, from the lower Otekaike Limestone (?Duntroonian Stage) is identified informally as W species. It is probably congeneric with a new species, referred to here as Wm, which is proposed elsewhere (by Fordyce) as the basis for a new genus and family of Platanistoidea. The specimen, OU 22125, is represented by a partial skull, teeth, earbones and post-cranial elements. The scapula retains a small coracoid process and a supraspinous fossa, which contrasts with the loss of these features in younger Platanistoidea, a loss which Muizon (1991) cited as synapomorphic of Platanistoidea. This reinforces the idea that the Platanistoidea should probably be redefined. The second specimen, OU 22126 (upper Otekaike Limestone, Waitakian Stage), is a small odontocete with a long rostrum, gracile, procumbent teeth, and superficially squalodont-like earbones. It appears closest amongst described odontocetes to the early Miocene (equivalent to upper Otaian or Altonian Stages) Dalpiazina ombonii from Italy. OU 22126 is provisionally referred to a new genus and species (as yet unnamed) within the monotypic family Dalpiazinidae. OU 22126 thus expands the geographic range, stratigraphic range and concept of the family.

ix, 99 leaves : ill. (some col.), map ; 30 cm.

1992Samson