Serrasalmidae

The Serrasalmidae (serrasalmids) are a family of characiform fishes native to freshwater habitats of South America. They include more than 90 species. The name means "serrated salmon family", which refers to the serrated keel running along the belly of these fish. Fish classified as Serrasalmidae are also known by these common names: pacu, piranha, and silver dollar. These common names generally designate differing dental characteristics and feeding habits.

==Description== Serrasalmids are medium- to large-sized characiform bony fishes that reach about long, generally characterized by a deep, laterally compressed body with a series of midventral abdominal spines or scutes, and a long dorsal fin (over 16 rays). Most species also possess an anteriorly directed spine just before the dorsal fin extending from a supraneural bone; exceptions include members of the genera Colossoma, Piaractus, and Mylossoma.