Search Result for "heterocercal fin":
Wordnet 3.0

NOUN (1)

1. a tail fin with unequal lobes in which the vertebral column turns upward into the larger lobe as in sharks; 



WordNet (r) 3.0 (2006):

heterocercal fin
    n 1: a tail fin with unequal lobes in which the vertebral column
         turns upward into the larger lobe as in sharks [ant:
         homocercal fin]