Dental Morphology and Taxonomic Assessment of Key Serrasalmidae Genera (Actinopterygii: Teleostei: Characiformes)

The family Serrasalmidae, which is exclusively formed of Neotropical freshwater Characiformes, comprises 18 South American genera with 105 described species. Most of this species is represented in the fossil record, with one species now extinct. Reviewing the teeth morphology of this family is of great relevance, given the recurrent use of dental morphology in taxonomic classification and in identifying fossil teeth within the family’s extinct forms. The goal of this study was to review the dental morphology and taxonomy of the main current representatives of this family. The specimens analyzed are in the ichthyological collection of the State University of Rio de Janeiro (UERJ). The specimens studied (Metynnis fasciatus Ahl 1931, Metynnis guaporensis Eigenmann 1915, Myloplus arnoldi Ahl 1936, and Pygocentrus nattereri Kner 1858) were identified using bibliographic references, dissected, and their skeletons were prepared using dermestid beetles. The dentary and premaxillary bones were then extracted for detailed analysis. The teeth of Myloplus arnoldi and Metynnis are molariform, with slightly elevated and convex crowns, asymmetrical cusps, external ones larger and darker (brown) than internal ones (white), broad roots, laterally long and deeply anchored in the dentary, and a wide, smooth surface. These analyses allowed us to identify differences in the heterodonty patterns between the two genera. Pygocentrus nattereri's teeth are caniniform, with long, flat, high crowns, sharp serrated edges, broad conical roots tightly set into the dentary, and a smooth, triangular, whitish surface. In conclusion, this study deepens the discussion on the relationship between dental morphology and taxonomic classification of this family, along with its fossil identification. The data from this study will contribute to a better understanding of morphological–taxonomic relationships, offering a more categorized view of Serrasalmidae dental morphological traits.