new species:
Nans indefessus Mirande, Aguilera & Azpelicueta, 2004

type locality:
Argentina, Province of Salta, Orán, río Bermejo basin, río Pescado at Estancia Anta Muerta (22°54,3’S, 64°28,2’W); Holotype CI-FML 4000 (male, 49,4 mm SL)

published in:
Mirande, J.M., G. Aguilera & M. Azpelicueta (2004):
A new genus and species of small characid (Ostariophysi, Characidae) from the upper río Bermejo basin, northwestern Argentina.
Revue Suisse de Zoologie 111 (4): 715-728

abstract (from publication):
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.

distribution (from publication):
The specimens were collected in the río Anta Muerta and arroyo Colorado, tributaries of the río Blanco, and in the río Pescado; all in the upper río Bermejo basin, in the province of Salta, Argentina. The specimens were collected in areas of streams or rivers with gravel bottom, low depth, and clear, rapidly flowing water. Submerged vegetation was scarce.