het·er·o·cer·cal 
(hĕt′ə-rō-sûrkəl)
(hĕt′ə-rō-sûrkəl)adj.
Relating to, having, or being a tail fin in which the upper lobe is larger than the lower and the vertebral column extends into the upper lobe, as in sharks.
[HETERO- + Greek kerkos, tail + -AL1.]
heterocercaltail of a leopard shark
Triakis semifasciata