With its short and pointed rostrum, the small fossil dolphin Brachydelphis mazeasi, from late middle to early late Miocene deposits of Chile and Peru, was originally described as an unusual member of the family Pontoporiidae (Cetacea, Odontoceti), presently only represented by the long-snouted Pontoporia blainvillei, a relict species from the eastern coast of South America. However, the phylogenetic relationships of Brachydelphis were debated in subsequent works. Based on a sample of well-preserved specimens from the late Miocene of the Pisco Formation (Tortonian, about 9 Ma) in the Sacaco Basin, southern coast of Peru, we describe a new species of Brachydelphis, B. jahuayensis, sp. nov. Also recorded in Chile, B. jahuayensis differs mostly from the type species in its considerably longer snout and higher tooth count. From a functional standpoint, the new species is interpreted as less specialized for suction feeding than the type species, relying more on its toothed jaws for prey capture. The inclusion of the long-snouted B. jahuayensis in future phylogenies will likely provide further support to the referral of Brachydelphis to the family Pontoporiidae. Finally, a review of the Mio-Pliocene vertebrate levels of the Pisco Formation in the Sacaco Basin clarifies the marine mammal content, succession, and stratigraphic correlation of each level, especially in the Aguada de Lomas locality.
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