A new genus and species of small characid (Ostariophysi, Characidae) from the upper río Bermejo basin, northwestern Argentina

Abstract

A new genus and species of small characid is described in this paper. The new genus, Nans gen. n., is diagnosed by the combination of: ii,7-8 dorsal-fin rays, 10-15 branched anal-fin rays, 5 teeth in the inner premaxillary row, rotation of the pelvic bone about 90°, rotation of the pelvic fin muscles, pelvic fin curved and forming a complete tube in mature males, incomplete foramen for exit of the olfactory nerve in the lateral ethmoid. Other characters which help in the identification of Nans are the large subcircular foramen in the dorsal vomerine lamella which articulates with the mesethmoid, the absence of an extrascapular sensory canal in the postemporal, and a laterosensory canal in the anguloarticular. The type species, Nans indefessus sp. n. was collected in the río Anta Muerta and arroyo Colorado, tributaries of the río Blanco, and in the río Pescado, upper río Bermejo basin, Salta, Argentina.