Redescription of Astyanax obscurus (Hensel, 1870) and A. laticeps (Cope, 1894) (Teleostei: Characidae): Two valid freshwater species originally described from rivers of Southern Brazil

Abstract

Astyanax obscurus and A. laticeps are redescribed. Both species were originally described from the laguna dos Patos system, Rio Grande do Sul, Brazil. The deepest and most robust body area close to the middle of the pectoral fins length, robust head, snout short and abrupt, body depth smaller than 41% of SL, reduced number of branched anal-fin rays, presence of one or two humeral spots, and a dark midlateral body stripe extending to the tip of the middle caudal-fin rays include both in the A. scabripinnis species complex. The presence of two humeral spots (vs. one), external row of the premaxillary with pentacuspid teeth (vs. tricuspid), and absence of bony hooks in all fins in males (vs. presence in anal and ventral fins) distinguish A. obscurus from A. laticeps. These species distinguish from species of this complex by meristic and morphometric characters and color pattern. An identification key for the species of genus occurring in the laguna dos Patos system is presented. © 2010 Sociedade Brasileira de Ictiologia.