Sagmatias was a genus of dolphins, defined in 1866 by Edward Drinker Cope with Peale's dolphin as type species, described as "Sagmatias amblodon". 
It has been proposed to resurrect the genus to include four species of oceanic dolphins currently classified in the genus "Lagenorhynchus". Mitochondrial DNA studies have indicated that Pacific white-sided dolphin, Peale's dolphin, dusky dolphin and hourglass dolphin are more closely related to dolphins in the Lissodelphininae subfamily, than to the two other members of the genus: Atlantic white-sided dolphin and white-beaked dolphin. This phylogenetic relationship is further supported by cladistic analysis of morphological characters. However, resurrection of the genus "Sagmatias" has not been accepted by the Society for Marine Mammalogy's taxonomic Committee, because the finer details of the phylogenetic relationships between the four species in the proposed "Sagmatias" genus and the four species of dolphins in the genus "Cephalorhynchus" remains to be resolved. Genetic and bioacoustical evidence suggest that Peale's dolphin and hourglass dolphin are closer related to the "Cephalorhynchus" species than to the Pacific white-sided dolphin and dusky dolphin, which, if true, would make the genus "Sagmatias" paraphyletic.
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