Cyprinodontiformes
Mummichog (Fundulus heteroclitus heteroclitus)
Scientific classification
Kingdom: Animalia   Phylum: Chordata   Class: Actinopterygii   Order: Cyprinodontiformes Berg, 1940
Families
Anablepidae (four-eyed fish) Aplocheilidae Cyprinodontidae (pupfish) Fundulidae Goodeidae Poeciliidae (live-bearers) Profundulidae Rivulidae Valenciidae

The Cyprinodontiformes is an order of ray-finned fish, also called the Microcyprini, and comprising mostly small, fresh-water fish. They are closely related to the Atheriniformes and are occasionally included with them. Many popular aquarium fish, such as killifish and live-bearers, belong here.

Members of this order are notable for inhabiting harsh environments, such as saline or very warm waters, water of poor quality, or isolated situations where no other types of fish occur. They are typically omnivores, and often live near the surface, where the oxygen-rich water compensates for environmental disadvantages.