The Collaborative International Dictionary of English v.0.48:

Caudal \Cau"dal\, a. [L. Cauda tail. Cf. Coward.]
   Of the nature of, or pertaining to, a tail; having a
   tail-like appendage.
   [1913 Webster]

         The male widow-bird, remarkable for his caudal plumes.
                                                  --Darwin.
   [1913 Webster]

   Caudal fin (Zool.), the terminal fin (or "tail") of a fish.
      [1913 Webster]

WordNet (r) 3.0 (2006):

caudal fin
    n 1: the tail of fishes and some other aquatic vertebrates [syn:
         tail fin, caudal fin]