A new species of Rhamphichthys (Gymnotiformes: Rhamphichthyidae) from the Amazon Basin

Rhamphichthys heleios, new species, is described from the Amazon Basin in Brazil, being known from lakes and channels associated with the floodplains of large rivers. The new species is readily distinguished from all other congeners by a unique color pattern, composed of a series of dark irregular rounded blotches along the lateral body surface over the lateral line, and by the absence of clearly formed saddles across the dorsum. Comments on the taxonomy and use of color pattern for the systematics of Rhamphichthys are made based on examination of extensive materials in museum collections, and a key to the species of the genus occurring in the Amazon Basin is provided.