Summary.The skulls and cranial muscles of the primitive characinsCreatochanesandBryconare described. Other Characinoidei, which have been selected to illustrate the remarkable adaptive radiation of the suborder, are compared with them in detail. They are:Myleus, a deep‐bodied herbivore specialized for biting pieces from plants;Serrasalmus, the piranha, a predator which bites pieces of flesh from large prey;Pyrrhulina, a surface feeder;Leporinus, a herbivore with jaws and teeth suited for nibbling rather than biting;Hoplias, a long‐jawed predator; andAnisitsia, a detritus feeder which is convergent with the grey mull