Lissodelphis

Lissodelphis is a genus of dolphin, family Delphinidae, known as the right whale dolphins and comprising two living species, the northern right whale dolphin and the southern right whale dolphin. Predominantly black with white undersides, both species are slender, smaller members of the delphinid family and are among the few cetaceans without a dorsal fin or ridge, a trait shared with right whales that likely gave the genus its common name; the northern species is the only finless dolphin in the Pacific and the southern species the only one in the Southern Hemisphere. Despite being known to science since the nineteenth century, comparatively little is documented about their life history and behavior.