A Morphological Comparison of Skulls of the Finless Porpoise Neophocaena phocaenoides from the Indian Ocean, Yangtze River and Japanese Waters

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Skull measurements of the finless porpoise were compared among the Indian Ocean, Yangtze River and Japanese waters. Codylobasal lengths of physically mature specimens were greatest in Japanese waters and smallest in the Indian Ocean as suggested by earlier studies. Analyses of covariance indicated that individuals in the Indian Ocean have relatively shorter and wider rostrums than those in the other areas, while specimens. from Japan have relatively narrower zygomatic widths. Multiple group principal component analysis discriminated the Indian Ocean specimens from the others, but failed to separate the Yangtze River and the Japanese specimens. We consider that geographic differences observed in the finless porpoise are comparable with intraspecific variation reported in a few well examined odontocete species, and not enough to warrant separating Neophocaena into different species. Although overall resolution of taxonomy awaits further studies, the present information supports arguments for classifying finless porpoises in the Indian Ocean and other areas at the subspecific level.
日本哺乳類学会の論文