In recent years, several species of Astyanax with similar counts of scales (33-36 on lateral line, 6-7/5-6 transverse) and anal fin-rays (iv-v + 21-23) to those of A. eigenmanniorum were described from eastern Brazil and northern Argentina (Almiron et al, 2002; Azpelicueta & Garcia, 2000; Azpelicueta et al. 2002a, 2002b, 2003; Casciotta et al., 2003; Casciotta & Almiron, 2004; Melo, 2001; Miquelarena et al., 2005; Miquelarena & Menni, 2005; Mirande et al., 2006). Several of these species, plus a few others, share the presence of gradually decreasing dentary teeth and variably expanded premaxillary teeth. This group of species is composed by A. giton Eigenmann and A. hastatus Myers from eastern Brazil, A. ojiara Azpelicueta & Garcia , A. troya Azpelicueta, Casciotta & Almiron , A. leonidas Azpelicueta, Casciotta & Almiron , A. pynandi Casciotta, Almiron, Bechara, Roux & Ruiz Diaz , A. ita Almiron, Azpelicueta & Casciotta from northeastern Argentina, and A. chico Casciotta & Almiron from northwestern Argentina. Additionally, all these species with the exceptions of A. hastatus and A. ita have hooks on anal, pelvic, pectoral, and/or dorsal, caudal fins.
The aim of this paper is to describe a new species from the endorheic RíoSalí basin, northwestern Argentina, which shares with the mentioned species the gradually decreasing dentary teeth and expanded premaxillary teeth.
The genus Astyanax is currently diagnosed by a combination of several broadly distributed features among Characidae, and there are no studies supporting neither its monophyly nor the monophyly of some species complex within the genus. We assign this new species to genus Astyanax following its traditional definition (Eigenmann, 1917), considering that the new taxon shares some presumably apomorphic character states with species also assigned to this genus.
