Astyanacinus Eigenmann, 1907

Astyanacinus was considered closely related to Astyanax, differing from that genus only by the form of the mouth. In Astyanacinus the maxilla is long and does not form an angle with the premaxilla (Eigenmann, 1921). This character state is present in other genera of the Characidae, as Dectobrycon, Hollandichthys, Oligosarcus, and Pseudochalceus. Among the presumably apomorphic features of Astyanacinus, the rounded humeral spot and the presence of circulii on the posterior field of scales [(pers. obs. in A. moorii (Boulenger)] and the presence of chromatophores densely concentrated in the focus of scales (pers. obs. in A. multidens Pearson), would relate this genus with the Astyanax bimaculatus -group, while the presence of chevron-shaped marks on the flanks is shared with Astyanax superbus Myers and Hyphessobrycon bifasciatus, among other species. These alternatives could relate Astyanacinus both with the Astyanax clade or with the Hyphessobrycon luetkenii clade and it is preferable to leave this genus as incertae sedis pending its inclusion in a phylogeny of the family.