protocercal tail Possibly the most primitive type of tail found in fish. The posterior end of the vertebral column is straight, dividing the tail fin into two equal lobes supported by fin rays. A Dictionary of Zoology. "protocercal tail ."

What is Protocercal?

adjective. Zoology. (In fishes) of, relating to, or designating a tail of a primitive (or larval) type, in which the end of the vertebral column is straight and the caudal fin is symmetrical and often continuous with the dorsal and anal fins; compare "heterocercal", "homocercal".

What is the meaning of Isocercal tail?

In fish, a tail in which there is an apparent symmetry between the dorsal and ventral regions, the fin rays being supported by equal-sized arches of the penultimate vertebrae as well as by the reduced, plate-like, ultimate vertebra. It is found e.g. in cod.