Comments: Lagenorhynchus obliquidens may be a Northern Hemisphere form of L. obscurus (Mead and Brownell, in Wilson and Reeder 1993, 2005). "Morphological differences exist between animals in the northeastern Pacific north of southern California and those 'resident' off Baja California" (IUCN 1991).
LeDuc et al. (1999) used cytochrome b gene sequences to examine phylogenetic relationships among delphinids and found that Lagenorhynchus albirostris (type species for the genus) and L. acutus are not closely related to each other or to nominal congeners; acutus was therefore assigned to the genus Leucopleurus. The remaining four Lagenorhynchus species are closely related to Lissodelphis and Cephalorhynchus and were placed in the genus Sagmatias. However, this revision has not been widely accepted and, pending further evidence, the mammal checklists by Baker et al. (2003) and Mead and Brownell (in Wilson and Reeder 2005) maintained acutus and obliquidens in the genus Lagenorhynchus.