Description
Piranhas are normally about 14 to 26 cm long (5.5 to 10.25 inches), although some specimens have been reported to be up to 43 cm (17.0 inches) in length.
Serrasalmus, Pristobrycon, Pygocentrus and Pygopristis are most easily recognized by their unique dentition. All piranhas have a single row of sharp teeth in both jaws; the teeth are tightly packed and interlocking (via small cusps) and are used for rapid puncture and shearing. Individual teeth are typically broadly triangular, pointed and blade-like (flat in profile). There is minor variation in the number of cusps; in most species, the teeth are tricuspid with a larger middle cusp which makes the individual teeth appear markedly triangular. The exception is Pygopristis, which has pentacuspid teeth and a middle cusp usually only slightly larger than the other cusps. In the scale-eating Catoprion, the shape of their teeth is markedly different and the premaxillary teeth are in two rows, as in most other serrasalmines.
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