Tetras, short for Tetragonopterus, although no longer in use phylogenetically / taxonomically, is the name given to a group of small-statured  freshwater Characins from Central and South  America and tropical  Africa.  The name, Greek for “four-sided wing” refers to the four unpaired fins, which characterize most but not all tetras.  These are the dorsal, anal, caudal and adipose fins