The Collaborative International Dictionary
Diphycercal
Diphycercal \Diph`y*cer"cal\, a. [Gr. difyh`s double (di- = di`s- twice + fy`ein to produce) + ke`rkos tail.] (Anat.) Having the tail fin divided into two equal parts by the notochord, or end of the vertebral column; protocercal. See Protocercal.
Wiktionary
diphycercal
a. (context zoology English) Describing a symmetric tail fin in which the vertebral column extends to the tip