Procerusternarchus pixuna, a new genus and species of electric knifefish (Gymnotiformes: Hypopomidae, Microsternarchini) from the Negro River, South America

ABSTRACT. Procerusternarchus pixuna, a new genus and species of hypopomid gymnotiform, is described from several tributaries of Negro River, Amazonas State, Brazil. The new genus is included in the tribe Microsternarchini with the genera Microsternarchus and Racenisia based on a phylogenetic analysis of 41 anatomical, morphometric, meristic, and electric organ discharge variable characters. The new taxon is distinguished from Microsternarchus and Racenisia by the apomorphic presence of a deep, enlarged myogenic electric organ, an electric organ discharge with a greatly reduced negative phase and the plesiomorphic condition of a fully-scaled body, whereas scales are absent from the upper back of Microsternarchus and Racenisia.