Osteology of Astyanax aurocaudatus, Eigenmann, 1913 (Pisces, Characidae), with notes on the validity of Carlastyanax, Géry, 1972. The taxonomic status of Astyanax aurocaudatus is difficult to interpret as no relevant osteological data are available to date. In the present paper we studied the osteological, morphometric and meristic characters of this species. The osteological characters of A. aurocaudatus found include the number and shape of premaxilla, maxilla and dentary teeth, second infraorbital separate from the preopercle, anal fins with pterygiophores that differ as towards the anterior, and presence of supra–orbital. These and other characters, body shape and coloring pattern, coincide with descriptions for the genus Astyanax. The characters describing the genus Carlastyanax therefore correspond to incorrect observations and the studied species is situated in the genus Astyanax. Carlastyanax is here considered a synonym of Astyanax.