diphycercal
Pronunciation: /ˌdɪfɪˈsəːk(ə)l/
adjective
Zoology- (of a fish’s tail) approximately symmetrical and with the vertebral column continuing to the tip, as in lampreys. Contrasted with heterocercal, homocercal.
Origin:
mid 19th century: from Greek diphu- 'of double form' + kerkos 'tail' + -al