Phylogenetics and diversification of the neotropical Serrasalminae (Ostariophysi: Characiformes)

The phylogenetics and fossil record of Serrasalminae (piranhas and pacus) were investigated to reconstruct the evolutionary history of this diverse characiform lineage. Serrasalmine phylogenetic relationships were inferred based on morphological and molecular data. The morphological dataset consists of 100 newly described and previously published osteological characters that were analyzed by maximum parsimony. The molecular dataset comprises sequences of the 5\u27 coding region of rag1, the second intron of rag1, and rag2. These sequences were combined and analyzed using maximum parsimony and Bayesian analysis. Both the morphological and molecular datasets strongly support three subgroups of serrasalmines: the basal clade consisting of Colossoma, Mylossoma, and Piaractus; the piranha clade with basal Metynnis; and the Myleus clade. Acnodon\u27s position was in conflict in the two analyses; it was placed as the sistergroup to the Myleus clade in the molecular analysis, versus the sister group to both the Myleus clade + piranhas in the morphological analysis. Serrasalmine fossils are used to provide minimum dates of origin for serrasalmine lineages. These fossils, both newly described and reexamined here, date from the Late Cretaceous to Late Cenozoic. My phylogenetic placement of the fossils establishes a Late Cretaceous origin for the basal split of serrasalmines. This finding indicates that serrasalmines had originated minimally by the Late Cretaceous and diversified throughout the Cenozoic, with subgroups and species appearing modern by the mid-Miocene