Piranha

Piranhas belong to the subfamily Serrasalminae, which also includes closely related herbivorous fish including pacus.^[2] Traditionally, only the four genera Pristobrycon, Pygocentrus, Pygopristis and Serrasalmus are considered to be true piranhas, due to their specialized teeth. However, a recent analysis^{[citation needed]} showed that, if the piranha group is to be monophyletic, it should be restricted to Serrasalmus, Pygocentrus and part of Pristobrycon, or expanded to include these taxa plus Pygopristis, Catoprion, and Pristobrycon striolatus. Pygopristis was found to be more closely related to Catoprion than the other three piranha genera.^[2]

The total number of piranha species is unknown and new species continue to be described. In 1988, it was stated^[where?] that fewer than a half of the approximately 60 nominal species of piranhas at the time were valid. More recently (in 2003), one author^[who?] recognized a total of 38 or 39 species, although the validity of some taxa remains questionable.