Genus Lagenorhynchus Gray, 1846

Of the six species recognized in the genus, only L. obliquidens inhabits the North Pacific Ocean. Based on cytochrome b gene analysis, LeDuc et al. (1999) regarded Lagenorhynchus as polyphyletic and suggested splitting the genus into three genera, Lagenorhynchus Gray, 1846; Leucoplearus Gray, 1866; and Sagmatias Cope, 1866 . LeDuc et al. (1999) recommended placing L. obscurus, L. obliquidens, L. cruciger, and L. australis in the Genus Sagmatias . However, Mead and Brownell (2005) proposed relegating two of the genera as a subgenera of Lagenorhynchus . However, Sagmatias appeared polyphyletic by analysis of nuclear genes (McGowen et al. 2009). Lagenorhynchus obscurus and L. obliquidens were separated from the L. cruciger — L. australis group, which were more closely related to Cephalorhynchus . Although some taxonomists recognized Sagmatias as a distinct genus (Murakami et al. 2014), the IUCN Red List still uses the Mead and Brownell (2005) taxonomy for Lagenorhynchus (Hammond et al. 2012) . Since marine biologists have not reached an agreement on this genus, we have followed the taxonomy of Mead and Brownell (2005).