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|Death Valley pupfish, Cyprinodon salinus spawning|
T. N. Gill, 1865
Pupfish are a group of small killifish belonging to ten genera of the family Cyprinodontidae of ray-finned fish. Pupfish are especially noted for being found in extreme and isolated situations. They are primarily found in North America, South America, and the Caribbean region, but Aphanius species are from southwestern Asia, northern Africa, and southern Europe. As of August 2006, 120 nominal species and 9 subspecies were known.
The common name is said to derive from the mating habits of the males, whose activities vaguely resemble puppies at play. 
Carl L. Hubbs, a prominent fish biologist and one of the first people to take an interest in them, coined the name after he observed their "playful" circling and tussling, which is actually the aggressive behavior of territorial males. 
In spite of their name, the cyprinodontids are not closely related to Cyprinidae, or carp family. They were formerly considered near allies of the pikes and their relatives, as they share some features: a flat head with protractile mouth beset with cardiform, villiform, or compressed, bi- or tricuspid teeth, generally large scales, and the absence of a well-developed lateral line. However, they are now generally assigned to the order Cyprinodontiformes. Several forms occur in the fossil records of the Oligocene and Miocene beds of Europe.
- McGinnis, Samuel M. (2006). Field Guide to Freshwater Fishes of California (Revised ed.). University of California Press. p. 271.
- Berra, Tim M. (2001). Freshwater Fish Distribution. Academic Press. p. 348.
- Moyle, Peter B. (2002). Inland Fishes of California. Berkeley, California: University of California Press. pp. 326–239. ISBN 0-520-22754-9.
- Barlow, George W. (1961). "Social behavior of the desert pupfish, Cyprinodon macularius, in the field and in the aquarium". American Midland Naturalist. 65 (330-359).