Appearance, distribution, and genetic distinctiveness of Longman's beaked whale, Indopacetus pacificus

Longman's beaked whale, Indopacetus pacificus, was known previously from only two skulls. Here we describe four new specimens of this species from strandings in the western and central Indian Ocean. Two juveniles, previously misidentified from external morphology as Hyperoodon planifrons, were identified as I. pacificus through diagnostic characteristics of mitochondrial (mt) DNA sequences derived from the holotype of this species. Images of the external appearance and teeth of the species are presented for the first time. Comparison of the color pattern of these new specimens with that of "tropical bottlenose whales" sighted in the tropical Indian and Pacific oceans confirm that those unidentified whales represent L pacificus. Moore (1968) erected a new genus, Indopacetus, for this species (described initially as Mesoplodon pacificus) based primarily on cranial morphology. Phylogenetic analyses of short mtDNA fragments available from the specimens known to date were unable to resolve the validity of this genus. However, the diagnostic osteological features highlighted by Moore (1968) for Indopacetus were also observed in the new specimens. Rib count and number of fused cervical vertebrae may also be diagnostic. Rostrum depth at mid-length and melon shape further distinguish this species from Mesoplodon beaked whales. As such, we see no reason on morphological grounds to overturn Moore's (1968) proposal that Longman's beaked whale is sufficiently distinct to be afforded its own genus.