homocercal
adjective
ho·mo·cer·cal ˌhō-mə-ˈsər-kəl 
ˌhä-
1
of a fish tail fin : having the upper and lower lobes approximately symmetrical and the vertebral column ending at or near the middle of the base
2
: having or relating to a homocercal tail fin
Word History
First Known Use
1838, in the meaning defined at sense 1