A new species of Astyanax (Characiformes, Characidae) from the rio Apiacás, rio Teles Pires basin, with a discussion on its phylogenetic position

A new species of Astyanax Baird & Girard, 1854 is described from the rio Apiacás, a tributary of the rio Teles Pires, rio Tapajós basin, Mato Grosso state, Brazil. The new taxon can be distinguished from all congeners, except those belonging to the Astyanax bimaculatus species group and to the Astyanax orthodus species group, by the presence of a horizontally elongated to rounded humeral blotch. The new taxon can be readily distinguished from all species belonging to the A. bimaculatus species group and to the A. orthodus species group by presenting a distinct morphology in premaxillary and dentary teeth with conspicuous diastema (a teeth gap) between them. We also present a hypothesis about the phylogenetic relationships of the new taxon within Astyanax.