Cephalorhynchus is a genus in the dolphin family Delphinidae.
Extant species
It consists of six species:
{| class="wikitable"
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! Image !! Common name !! Scientific name !! Distribution
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|120px||Peale's dolphin|| C. australis||Southern South America
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|120px||Commerson's dolphin|| C. commersonii||Argentina including Puerto Deseado, in the Strait of Magellan and around Tierra del Fuego, and near the Falkland Islands, near the Kerguelen Islands in the southern part of the Indian Ocean
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|120px||Hourglass dolphin|| C. cruciger||Argentina, Chile, New Zealand
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|120px ||Chilean dolphin|| C. eutropia||coast of Chile
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|120px ||Heaviside's dolphin|| C. heavisidii||coast of northern Namibia at 17°S and as far south as the southern tip of South Africa
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|120px ||Hector's dolphin|| C. hectori||coastal regions of New Zealand
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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, the hourglass dolphin L. cruciger and Peale's dolphin L. australis are actually phylogenetically nested among the species of Cephalorhynchus, and they suggested that 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. In 2025 those two species were transferred to Cephalorhynchus.
According to a study in 1971, the Cephalorhynchus species are the only dolphins that do not whistle (no acoustic data are available for the hourglass dolphin). Peale's dolphin also shared with several Cephalorhynchus species the possession of a distinct white "armpit" marking behind the pectoral fin.
Subspecies are now recognized for the Commerson’s dolphin and the Hector’s dolphin.For the Commerson’s dolphins, there are two different populations, one in the Kerguelen Islands in the southern Indian Ocean and one in southern South America and the Falkland Islands.59% of the stomachs included red cod, 49% contained ahuru, and the most prevalent species found was arrow squid.Groups of 20 or more individuals have also been recorded, often splitting into smaller subgroups. Group composition ranges from strictly single-sex to mixed-sex. Groups with mothers and calves contained no adult males. About 91% of groups with two to five individuals were single-sex, while larger groups tended to be mixed-sex. However, because 82.8% of observed groups contained fewer than six individuals, most observed groups were sexually segregated.
The Commerson’s dolphin’s southern South American population has been subjected to harpooning and accidental capture in fishing gear. Evidence suggests that hundreds of Commerson’s dolphins were killed per year during the 1980s in southern Argentina and Chile.