What's the difference between diphycercal and heterocercal?

Diphycercal

Definition:

(a.) Having the tail fin divided into two equal parts by the notochord, or end of the vertebral column; protocercal. See Protocercal.

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Definition:

(a.) Having the vertebral column evidently continued into the upper lobe of the tail, which is usually longer than the lower one, as in sharks.

Example Sentences: