|difē, -fə̇+ adjective
Etymology: diphy- + -cercal
1. of a tail fin : having the upper and lower portions alike or nearly so and the vertebral column extending to the tip without any upturning
in lungfish and crossopterygians this symmetry is attained by the evolution of a diphycercal tail — A.S.Romer
2. : having a diphycercal tail fin