Latimeria chalumnae
The coelacanth was thought to have gone extinct with the dinosaurs until a living specimen was caught off South Africa in 1938, one of the great zoological surprises of the century. Its lobed, paddle-like fins move in an alternating gait unlike any other fish, and it gives birth to live young. It survives on deep volcanic slopes where cold upwelling water suits it; slow reproduction and accidental bycatch make it one of the rarest fish on Earth.