Astyanax viridis (Characiformes: Characidae), New Species from Southeastern Brazil

Astyanax Baird & Girard, 1854 is one of the most specific fish genera among the characiforms, occurring in freshwater environments between the United States and central Argentina. Astyanax viridis sp. n was described from specimens from southeastern Brazil, earlier identified as A. janeiroensis. These specimens are differentiated from A. janeiroensis holotype, mainly in the maximum maxilla length (35.1-38.9% HL), pelvic-anal fin distances (19.0-21.9% SL) and number of rays divided into anal fin (18-19), justifying its description as a new species. Astyanax viridis sp. n. it presents a horizontally triangular humeral spot (atypical in Astyanax), sharing it with A. laticeps, A. scabripinnis and A. serratus, forming a small exclusive group, inserted in the A. scabripinnis species complex, defined by the elongated body, with depth less than 40% SL and reduced number of rays in the anal fin (17-20). It differs from these three species in that it has 4 large teeth in the dentary (vs. 5), by the head length (26.2-27.9% HL vs. 20.9-21.3%; 23.0-25.2% and 33.9-35.3% HL, in A. laticeps, A. scabripinnis and A. serratus, respectively) and pelvic-anal fin distance (19.1-21.9% SL vs. 30.0-31.5%; 22.0-24.9% and 28.8-31.8% SL in A. laticeps, A. scabripinnis and A. serratus, respectively). Astyanax viridis sp. n. occurs sympatrically with several other species of the genus, A. aff. bimaculatus (A. bimaculatus complex), A. giton, A. hastatus, A. parahybae and A. taeniatus (A. fasciatus complex) and A. intermedius (A. scabripinnis complex), being found in backwater areas in streams and rivers. The new species occurs in the main coastal basins, in the states of Espírito Santo, Minas Gerais, Rio de Janeiro and São Paulo.