Dorsal Fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, cetaceans (whales, dolphins, and porpoises), and the (extinct) ichthyosaurs. Depending on the species, an animal may have one or two of them.

Wildlife biologists often use the distinctive nicks and wear patterns which develop on the dorsal fins of large cetaceans to identify individuals in the field.

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