Dorsal fin

Dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fish, certain marine mammals (like dolphins), and the (extinct) ichthyosaurs. Depending on the species, an animal may have one or more dorsal fins. The dorsal fin aids the animal in sudden turns and stops.

Function

The main purpose of the dorsal fin is to stabilize the animal against rolling and assist in sudden turns. Some animals have developed dorsal fins with protective functions, such as spines or venom. Many catfish can lock the leading ray of the dorsal fin in an extended position to discourage predation; others, like lionfish, have venomous spines in their dorsal fins.

Anatomy

The bony or cartilaginous bones that support the base of the dorsal fin are called pterygiophores.

In different animals

Different animals have developed dorsal fins with different functions.

Fish

In many fish, the dorsal fin(s) serve to protect against predation, and many have spines in them that are venomous, like the lionfish.

Dolphins

In dolphins, the dorsal fin acts as a keel, preventing the dolphin from rolling and providing stability.

Ichthyosaurs

In the extinct ichthyosaurs, which were not fish, the dorsal fin was similar to that of dolphins.

See also

• Fin
• Fish anatomy
• Ichthyosaur
• Dolphin

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