Abstract
Astyanax utiariti, new species, is described from the upper rio Tapajós drainage, Mato Grosso, Brazil. Astyanax utiariti has a horizontally oval black humeral spot, a lozenge-shaped caudal-peduncle spot, continuing to the tip of the middle caudal-fin rays, and two brown bars in the humeral region that allows its inclusion in the A. bimaculatus species group. It also possesses a black stripe extending along midlateral body. The new species is distinguished from its congeners by a reticulate scale pattern, a black longitudinal stripe, toothless maxilla, larger dentary teeth and teeth of the inner row of the premaxilla with five to seven cusps, body depth 33.3-39.9% of standard length (SL), head length (HL) 23.9-26.4% of SL, caudal-peduncle depth 12.0-13.4% of SL, orbital diameter 28.5-34.3% of HL, interorbital width 32.7-38.4% of HL, 36-38 perforated scales along the lateral line, and 22-26 branched anal-fin rays.
Highlights
The genus Astyanax Baird & Girard is a speciose group of Neotropical characid fishes, comprising almost one hundred described species (Bertaco & Lucena, 2006) and occurring in diverse habitats within freshwater drainages from the southern United States to central Argentina
The new species is distinguished from species of this group by the following combination of characters: a reticulate scale pattern, a black longitudinal stripe, a toothless maxilla, larger dentary teeth, teeth of the inner row of the premaxilla with five to seven cusps, body depth 33.3-39.9% of standard length (SL), predorsal distance 51.7-55.5% of SL, caudal peduncle depth 12.0-13.4% of SL, head length 23.9-26.4% of SL, orbital diameter 28.534.3% of HL, interorbital width 32.7-38.4% of HL, 36-38 perforated scales along the lateral line, and 22-26 branched anal-fin rays (25-29 total)
Astyanax utiariti possesses a black, oval humeral spot, that is horizontally elongate, a black, lozenge-shaped caudalpeduncle spot continued into the middle caudal-fin rays, and two brown bars on the humeral region
Summary
The genus Astyanax Baird & Girard is a speciose group of Neotropical characid fishes, comprising almost one hundred described species (Bertaco & Lucena, 2006) and occurring in diverse habitats within freshwater drainages from the southern United States to central Argentina. The current definition of Astyanax is based on a combination of characters proposed by Eigenmann (1917). In the last years, Garutti (1995, 1998, 1999, 2003) and Garutti & Britski (1997, 2000) revised a group of Astyanax species with a combination of the following characters: a horizontally oval, black humeral spot, a lozenge shaped caudal-peduncle spot, continuing to the tip of the middle caudal rays, and two brown vertical bars in the humeral region.
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