Megapiranha

Megapiranha is a genus of extinct serrasalmid fish from the Late Miocene (between 8-10 million years ago) of Argentina described in 2009. Megapiranha reached lengths of up to 3 feet (1 meter) long, four times the size of the modern-day piranha. It differs from modern-day piranhas in that it's teeth are arranged in a zig-zag, intermediate pattern; a transitional form that bridges the evolutionary gap between flesh-eating piranhas and their plant-eating relatives. Present-day piranhas have a single row of teeth, while the piranhas relatives, the Pacu, have two rows of square teeth used for crushing fruits and seeds. The discovery of Megapiranha suggests that the two rows in pacu were compressed to form a single row in piranhas. The teeth of Megapiranha also suggest that the creature was most likely omnivorous. Megapiranha also had seven teeth in its jaw, as opposed to the six teeth found in modern piranhas.

The type specimen was originally collected in a riverside cliff in northeastern Argentina in the early 1900s. However, it remained in storage until paleontologist Alberto Cione of Argentina's La Plata Museum rediscovered the specimen in 1980s. The genus and species were formally described in the scientific literature in the Journal of Vertebrate Paleontology in 2009.