Spiracle (vertebrates)

[3][4] In many species of sharks and all rays the spiracle is responsible for the intake of water into the buccal space before being expelled from the gills.

[9] Coelacanths have closed off spiracles which may be a product of their deepwater lifestyle and loss of air breathing lungs.

Acipenseriformes including sturgeons and paddlefish have small seemingly vestigial spiracles much like coelacanths[11] further reduced in Holostei[12] and completely absent in Teleostei, the clade containing 96% of all extant species of fish.

[15] The spiracle is still found in all cartilaginous fish except requiem sharks, hammerhead sharks, and chimaeras, and is found in some primitive bony fishes (coelacanth, sturgeon, paddlefish and bichirs).

It is also seen as an otic notch in the skull of the extinct labyrinthodonts, and is thought to be associated with the ear opening in amniotes and frogs.