Megapiranha paranensis is an extinct serrasalmid characin fish from the Late Miocene (8–10 million years ago) of Argentina described in 2009. It is thought to have been up to a meter in length. The holotype consists only of premaxillae and a zigzag tooth row; the rest of its body is unknown. This dentition is reminiscent of both the double-row seen in pacus, and the single row seen in the teeth of modern piranhas, suggesting that M. paranensis is a transitional form.