• (a.) Having a caudal fin extending around the end of the vertebral column, like that which is first formed in the embryo of fishes; diphycercal.
Pro`to·cer'cal adjective [ Proto- + Greek ... the tail.] (Zoology) Having a caudal fin extending around the end of the vertebral column, like that which is first formed in the embryo of fishes; diphycercal.