Epibranchial organs in lower teleostean fishes*

Epibranchial organs, consisting of a paired pharyngeal diverticulum, occur in some osteo‐glossiform, cypriniform, gonorynchiform and clupeiform fishes. They appear to have been independently developed during the evolution of the fishes of each of these four lineages, and constitute one of a series of gut specializations associated with microphagus habits. On the basis of adult gill‐arch structure, the organs always seem to be formed in the same way, by the secondary upgrowth, posterior to the fifth epibranchial, of the ventral part of the fifth gill slit.