From Di... and Greek phýo, to produce, arise, and kérkos, tail.

Diphycercal caudal fin - externally and internally symmetrical, divided by the spine into equal upper and lower lobes. It is found in double-breathing fish and whole-headed fish, and in bony fish - in garganov and cod.

A caudal fin in which the axial skeleton extends to the posterior edge of the fin plate, dividing it into symmetrical upper and lower lobes. In phylogeny, it arises by secondary straightening of the skeletal axis of the heterocercal fin and by strengthening its upper blade.