Cheirolepis

Cheirolepis, shown here in a reconstruction by the 19th-century paleontologist and journalist Hugh Miller, lived in fresh waters of the Middle Devonian in what is now Scotland. It and several related fishes of this time are the most primitive ray-finned fishes known. Note its highly streamlined body, capable of rapid swimming. Cheirolepis also bore pointed teeth in a large mouth (not visible on this drawing), suggesting it was a predator. Also note its heterocercal (asymmetrical) tail, similar in shape to that of modern sharks and their kin. This is an extermely primitive feature, which almost all living ray-finned fish have lost.

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