Abstract
A new Astyanax is described from the rio Taquari-Antas basin, rio Jacuí drainage, laguna dos Patos system, Rio Grande do Sul State, Brazil. The new species is distinguished from its congeners inhabiting the rio Uruguay, laguna dos Patos and rio Tramandaí basins by the presence of two vertically elongated humeral spots, the anterior humeral spot with the upper portion wider than the lower portion and slightly directed forward, 37-39 perforated scales along the lateral line, 14 scale rows around caudal peduncle, 2-4 maxillary tricuspid teeth, 24-28 branched anal-fin rays, bony hooks on all fins of mature males, and conspicuous caudal peduncle spot. Furthermore, the new species differs from its congeners by body depth (37.9-45.9% of standard length), preanal distance (62.4-69.1% of SL), anal-fin base length (29.7-35.6% of SL), and orbital diameter (29.5-38.2% of head length).
Highlights
Astyanax Baird & Girard is a species-rich characid genus, composed of 145 valid species, widely distributed on the Neotropical region from southern United States to central Argentina (Eschmeyer, 2014)
During a revisionary study of Astyanax from these basins, an endemic new species was recognized from tributaries of the rio Taquari-Antas, rio Jacuí drainage, laguna dos Patos system, which is described
Along the description counts are followed by the number of occurrence in parentheses, and the value observed on the holotype is marked with an asterisk
Summary
Astyanax Baird & Girard is a species-rich characid genus, composed of 145 valid species, widely distributed on the Neotropical region from southern United States to central Argentina (Eschmeyer, 2014). According to recent phylogenies Astyanax does not represent a monophyletic group (Javonillo et al, 2010; Mirande, 2010; Oliveira et al, 2011), and so far it has been defined by a combination of characters proposed nearly a century ago by Eigenmann (1921, 1927): two rows of premaxillary teeth, five teeth in the inner premaxillary series, lateral line complete, adipose fin present, and caudal fin scaleless. Some of these characters are shared by other genera in the Characidae (e.g., Hemigrammus Gill, Hyphessobrycon Durbin, and Moenkhausia Eigenmann & Eigenmann, 1921, 1927). During a revisionary study of Astyanax from these basins, an endemic new species was recognized from tributaries of the rio Taquari-Antas, rio Jacuí drainage, laguna dos Patos system, which is described
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