The piranhas are oval fish, laterally compressed and with small scales, measuring between 25 and 60 cm long
They have poorly developed pectoral and pelvic fins, while the caudal and anal fins are quite broad.
They have a blunt head with powerful jaws armed with sharp triangular teeth that overlap like pruning shears and allow them to cut the flesh of their prey, almost always other fish, but also amphibians, birds and mammals.
Piranhas are associated in large banks and are attracted by the agitation of the waters and the smell of blood. They are extremely voracious and once excited, can turn a large mammal into a pile of bones in a short time, although that happens rarely. Cannibalism is also common.