Characiformes is an order of ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, there are a few thousand different species (based on Wikipedia, about 2,086), including the well-known piranha and tetras.

Characiformes is an order of ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, there are a few thousand different species (based on Wikipedia, about 2,086), including the well-known piranha and tetras.