See text Pristobrycon is a genus of piranhas from the Orinoco and Amazon Basins, as well as rivers in the Guianas.

No single morphological feature has been found that completely diagnoses this genus.

[1] The genus Pristobrycon was created by Eigenmann to include species which have intermediate characters between "the fierce Rooseveltiella [=Pygocentrus nattereri] without palatine teeth, and the less blood-thirsty Serrasalmus with a series of permanent teeth along the palatine".

The author designed P. calmoni as the type species of the genus.

One group is characterized by presence of the preanal spine (only P. calmoni) and the other group including the rest of the species assigned (P. careospinus, P. maculipinnis and P. striolatus) (Fink & Machado-Allison, 1992; Machado-Allison et al., 1989; Machado-Allison & Fink, 1996).