From Hetero... and Greek kérkos - tail.

Asymmetrical fin with different sized lobes, end of spine sharply bent upwards and entering the upper fin blade (sharks, sturgeons, etc.).

The caudal fin is a fin located on the tail of many aquatic animals: non-pinnipeds, fish, some marine mammals (cetaceans and sirens), as well as some extinct marine reptiles. Its shape is closely related to the type of movement.

Heterocercal - a caudal fin with blades of significantly different lengths, with the upper blade being longer and the caudal spine entering it. It is characteristic of cartilaginous fish and sturgeons, as well as - for the majority of armored and part of shovelnose fish.