Fig. 8

Body elongated; greatest depth contained 2.1 to 2.5 and caudal peduncle depth 7.0 to 8.0 times in SL; head length 3.1 to 3.5, predorsal distance 1.7 to 1.9 and caudal peduncle length 8.3 to 12.4 in SL; snout length 3.5 to 4.7, horizontal orbital diameter 2.2 to 2.6 and least interorbital width 2.5 to 2.7 in HL. Mouth terminal; inner row of premaxilla with 5 teeth, outer with 3 or 4, dentary with 9-12 and maxilla with 1 or 2 teeth. Lateral line complete, or occasionally discontinuous, with 19-26 pored scales; longitudinal series with 24-26 scales; transverse series above lateral line with 4, 4 ½ or 5 scale rows and below with 3, 3 ½ or 4 scale rows. Dorsal fin with 11 rays, pectoral fin with 11-13 rays, pelvic fin with 8 rays, anal fin with 24-27 rays and caudal fin with 19 rays. Ground color silvery; scales with dark-brown border, conferring reticulated pattern to body; one dark-brown humeral spot; anterior half of caudal peduncle with light-beige area. Hyaline fins, except caudal fin; posterior portion of caudal peduncle and proximal third of caudal fin with conspicuous black transverse bar occupying their whole depth.

Maximum standard length. 45.0 mm.

Distribution. Upper rio Paraná and río Paraguay basins.

Remarks. Some specimens of M. australe were identified as M. aff. sanctaefilomenae by Graça, Pavanelli (2007). Both species occur in the upper rio Paraná floodplain, where M. australe has been captured since 1989 by the Nupélia staff. Moenkhausia australe can be distinguished by having lateral line completely pored, rarely disrupted (vs. lateral line incompletely pored, in M. sanctaefilomenae). Despite the general morphological similarity between M. australe, M. forestii and M. sanctaefilomenae, Benine et al. (2009) and Mariguela et al. (2013), in molecular analyses, considered them as different species. Moenkhausia australe was described from the lower río Paraguay basin, and it was considered a junior-synonym of M. sanctaefilomenae by Eigenmann (1917), until Benine et al. (2009) revalidated it. Re-analyzing the material hosted at Coleção Ictiológica do Nupélia, the older occurence from 1989 (NUP 10677, NUP 10678, NUP 10680, previously identified as M. sanctaefilomenae) was found, few years after the filling of the Itaipu Reservoir and the consequent inundation of the Sete Quedas Falls. Because of the earliest record occurred after the Itaipu Dam building, M. australe is considered a possible non-native species from the upper rio Paraná.