A new species of Astyanax tetra has been described from the upper Tocantins River drainage in central Brazil in the most recent issue of the journal Neotropical Ichthyology.
Vinicius Bertaco, Fernando Carvalho and Fernando Jerep name the new tetra Astyanax courensis in a paper in the journal Neotropical Ichthyology.
The new tropical fish species was collected in a forested stream with clear water, and a substrate of small stones, submerged logs and roots.
It was found together with the poorly known Astyanax goyanensis, which is also redescribed in this study.
It can be distinguished from other members of the A. scabripinnis species group (to which it belongs) in having a combination of: prepectoral distance 23.7–27.8% standard length; body depth 27.4–33.1% standard length; caudal peduncle length 13.6–16.9% standard length; head length 24.9–28.2% standard length; eye diameter 24.9–31.9% head length; upper jaw length 40.6–50.0% head length; 8 pelvic-fin rays; 15–17 branched anal-fin rays; 35–36 lateral-line scales; 3–4 scale rows between the lateral line the and pelvic fin origin; one tooth on the maxilla; teeth on the lower jaw abruptly decreasing in size after the fourth tooth; a single humeral spot.
For more information, see the paper: Bertaco, VA, FR Carvalho and FC Jerep (2010) Astyanax goyanensis (Miranda-Ribeiro, 1944), new combination and Astyanax courensis, new species (Ostariophysi: Characiformes): two Characidae from the upper rio Tocantins basin, Central Brazil. Neotropical Ichthyology 8, pp. 265–275.