MAGOSTERNARCHUS, A NEW GENUS WITH 2 NEW SPECIES OF ELECTRIC FISHES (GYMNOTIFORMES, APTERONOTIDAE) FROM THE AMAZON RIVER BASIN, SOUTH-AMERICA

A new group of predaceous apteronotid electric fishes is described fro m recent trawl collections made in large, white- and black-water river channels of the Amazon Basin in Brazil. Magosternarchus, n. gen., is diagnosed by greatly enlarged jaws and teeth. The type species, Magost ernarchus raptor, n. sp., possesses uniquely enlarged premaxillary bon es and an associated hypertrophied mesethmoid. Magosternarchus duccis, n. sp., is unique in its strongly projecting lower jaw that includes and often extends dorsal to the upper jaw and snout. The only identifi able stomach contents in specimens of both species of Magosternarchus are tails of other gymnotiform fishes. Shared features of the ethmoid and jaw bones, mesopterygoid, opercle, gillrakers, basibranchials, and infraorbital laterosensory canal suggest that Magosternarchus is most closely related to Sternarchella.