Hyphessobrycon auca sp. n. is described from the Esteros del Iberá wetlands. Hyphessobrycon auca differs from the remaining species of the genus by the presence of one maxillary tooth with 5 cusps; dentary low with teeth decreasing in size anteroposteriorly; males with hooks in all fins; mature females with hooks on pelvic-fin rays; one humeral spot vertically elongated, bounded by a light area; a second lateral spot may be faint or well developed; a wide lateral band ending in a conspicuous caudal spot.Facultad de Ciencias Naturales y Muse
