Cephalorhynchus is a genus in the dolphin family Delphinidae. It consists of four species:

• Commerson's Dolphin, Cephalorhyncus commersonii
• Chilean Dolphin, Cephalorhyncus eutropia
• Heaviside's Dolphin, Cephalorhyncus heavisidii
• Hector's Dolphin, Cephalorhyncus hectori

The species have similar physical features - they are small, generally playful, blunt-nosed dolphins - but they are found in distinct geographical locations.

A recent phylogenetic analysis by May-Collado & Agnarsson (2006) indicates that 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 suggest that these two species should be transferred to the genus Cephalorhynchus. There is some acoustic and morphological support for this arrangement, at least with respect to Peale's Dolphin. According to Schevill & Watkins (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

• May-Collado, L., Agnarsson, I. (2006). Cytochrome b and Bayesian inference of whale phylogeny. Molecular Phylogenetics and Evolution 38, 344-354.
• Schevill, W.E., Watkins, W.A. (1971). Pulsed sounds of the porpoise Lagenorhynchus australis. Breviora 366, 1–10.

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