[3] However, there is consistent molecular evidence that the genus is polyphyletic[4] and several of the species are likely to be moved to other genera.

There is compelling phylogenetic molecular evidence that the genus Lagenorhynchus is polyphyletic, in that it currently contains several species that are not closely related.

[6] LeDuc, Perrin & Dizon 1999 found that white-beaked and Atlantic white-sided dolphins are phylogenetically isolated within the Delphinidae, where they are believed to be rather basal members of the family, along with the orca (subfamily Orcininae).

[9][10] This signal is also used by porpoises (Phocoenidae) and the pygmy sperm whales (Kogiidae), but is not found among other dolphins.

Peale's dolphin also shares with several Cephalorhynchus species the possession of a distinct white marking behind the pectoral (“armpit”) fin.