Astyanax dissensus

description

Description. Morphometric data summarized in Table 1. Body compressed and deep, with greatest body depth anterior to dorsal-fin origin. Dorsal profile of head straight or slightly concave from region above the eye to supraoccipital spine. Dorsal body profile convex from tip of supraocciptal spine to base of last dorsal-fin ray; straight from latter point to adipose fin origin. Ventral profile of body convex from mandibular symphysis to pelvic-fin origin, nearly straight to anal-fin origin, and posterodorsally slanted along anal-fin base. Caudal peduncle deep, nearly straight to slightly concave in the dorsal and ventral margins. Snout rounded from margin of upper lip to vertical through anterior nostrils. Head somewhat pointed anteriorly in lateral profile. Mouth terminal, jaw isognathous. Maxilla extending to vertical through anterior margin of orbit. Maxilla slightly widened anteroposteriorly. Two tooth rows in premaxilla; outer row with 2 (2), 3 (57) *, 4 (14), or 5 (2) pentacuspid teeth, central cusp longer; inner row with five teeth, gradually decreasing in length from the first to fifth with seven to nine cusps, except the first teeth with asymmetric five cups; central cusp t

Three new species of Astyanax from drainages of southern Brazil (Characiformes: Characidae)

diagnosis

Diagnosis. Astyanax dissensus differs from all congeners inhabiting the rio Uruguay basin, laguna dos Patos and rio Tramandaí systems, except A. ojiara, in having one heptacuspid tooth on maxillary (vs. tri- to pentacuspid teeth). From A. ojiara it differs by the head length (22.7 - 27.3 % vs. 27.3 - 29.5 % of SL) and by the presence of hooks on anal fin on males (vs. all fins with hooks). The following combination of characters distinguish A. dissensus from all others species of the genus (including species complex A. bimaculatus and A. scabripinnis): the presence of two humeral spots, the first spot vertically elongate, a conspicuous caudal spot, 35 - 39 perforated lateral line scales, 6 - 7 scale rows between dorsal-fin origin and lateral line, 22 - 28 branched anal-fin rays, predorsal region scaled, one heptacuspid maxillary tooth, body depth (37.2 - 44.2 % of SL), and head length (22.7 - 27.3 % of SL).

Three new species of Astyanax from drainages of southern Brazil (Characiformes: Characidae)

distribution

Distribution. Astyanax dissensus is known from the laguna dos Patos system and rio Uruguay drainage (Fig. 3). One specimen was captured from coastal lagoon of rio Tramandaí system (MCP 21119). Astyanax dissensus appears to be rare in the rio Tramandaí system because although the sampling efforts in the region it is not mentioned in the Malabarba et al. (2013).

Three new species of Astyanax from drainages of southern Brazil (Characiformes: Characidae)

etymology

Etymology. The specific epithet dissensus from Latin, disagreement, in reference to the larger maxillary heptacuspid tooth peculiar to the species and unusual in Astyanax species.

Three new species of Astyanax from drainages of southern Brazil (Characiformes: Characidae)