heterocercal

/ˌhɛtəroʊˈsʌrkəl/

Definitions of heterocercal

1. adjective

   possessing a tail with the upper lobe larger than the lower and with the vertebral column prolonged into the upper lobe
   antonyms:

   homocercal

   possessing a symmetrical tail that extends beyond the end of the vertebral column (as in most bony fishes)