new species:
Astyanax pampa Casciotta, Almirón & Azpelicueta, 2005

type locality:
Argentina, Province of Buenos Aires, arroyo Las Mostazas (38°05’S 61°27’W); Holotype: MACN-ict 8651 (63.7 mm SL, female)

distribution in Argentina:
– type locality: holotype; paratypes AI 134 (8), MHNG 2644.22 (4), AI 135 (2)
– Province of Buenos Aires, río Colorado; paratype AI 166 (2)

published in:
Casciotta, J.R., A.E. Almirón & M. Azpelicueta (2005):
Astyanax pampa (Characiformes, Characidae), a new species from the southernmost boundary of the Brazilian subregion, Argentina.
Revue Suisse de Zoologie 112 (2): 401-408

abstract (from publication):
Astyanax pampa sp.n., the new species of characid herein, is known from arroyo Las Mostazas, an Atlantic Ocean drainage, and the lower río Colorado basin. Astyanax pampa sp.n. is distinguished from all other Astyanax species by the possession of 17-20 branched anal-fin rays, one maxillary tooth unicuspidate to tricuspidate, short anal-fin base (24.2-30.3% of SL), and a long caudal peduncle (10.5-12.7% of SL).

distribution and habitat (from publication):
Astyanax pampa sp.n. is known from arroyo Las Mostazas and the lower río Colorado basin, both environments running through the south of Buenos Aires province into the Atlantic Ocean.
The arroyo Las Mostazas is a short stream with variable depth ranging from 0.60 to 1 m. The water was turbid because of rainfall, with slow current and muddy bottom. The lower río Colorado basin presently has a net of irrigation cannals, 0.30 to 1 m deep with the caudal varying between 0.20 to 3 m³/seg; the current velocity can reach 1.5 km/h.