See the text Pupfish are a group of small killifish belonging to ten genera of the family Cyprinodontidae of ray-finned fish.

[2] The common name is said to derive from the mating habits of the males, whose activities vaguely resemble puppies at play;[3] Carl L. Hubbs, a prominent ichthyologist 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.

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.

Pupfish on the island of San Salvador, Bahamas, have a large adaptive diversification in only two small lakes.

Three species of pupfish on the island of San Salvador, Bahamas, all live in salty lakes.

The Death Valley pupfish evolve 5–10 faster than average[citation needed] and are known for their abilities to survive in extremely hot waters.

Cyprinodon diabolis eat algae off a rock shelf near the surface of the deep pool they live in.

The Devils Hole pupfish (Cyprinodon diabolis) is a specific species native to Nevada.