''Cephalorhynchus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

in the

dolphin A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Delphinidae Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea. Close to forty extant species are recognised. They include several big species whose common names contain "whale" rather than "dolphin", such as the ...

Extant species

It consists of four species: The species have similar physical features—they are small, generally playful, blunt-nosed dolphins—but they are found in distinct geographical locations. A phylogenetic analysis in 2006 indicated the two species traditionally assigned to the genus ''

Lagenorhynchus ''Lagenorhynchus'' is a genus of oceanic dolphins in the infraorder Cetacea, presently containing six extant species. However, there is consistent molecular evidence that the genus is polyphyletic and several of the species are likely to be move ...

'', the

hourglass dolphin The hourglass dolphin (''Lagenorhynchus cruciger'') is a small dolphin in the family Delphinidae that inhabits offshore Antarctic and sub-Antarctic waters. It is commonly seen from ships crossing the Drake Passage but has a circumpolar distribut ...

''L. cruciger'' and

Peale's dolphin Peale's dolphin (''Lagenorhynchus australis'') is a small dolphin found in the waters around Tierra del Fuego at the foot of South America. It is also commonly known as the black-chinned dolphin or even Peale's black-chinned dolphin. However, si ...

''L. australis'' are actually phylogenetically nested among the species of ''Cephalorhynchus'', and they suggest these two species should be transferred to the genus ''Cephalorhynchus''. Some acoustic and morphological data support this arrangement, at least with respect to Peale's dolphin. According to a study in 1971, Peale's dolphin and the ''Cephalorhynchus'' species are the only dolphins that do not whistle (no acoustic data are available for the hourglass dolphin). Peale's dolphin also shares with several ''Cephalorhynchus'' species the possession of a distinct white "armpit" marking behind the pectoral fin.

References

Oceanic dolphins Cetacean genera Animals that use echolocation Taxa named by John Edward Gray {{whale-stub