Cyprinodontiformes - Toothcarps

Cyprinodontiformes is an order of ray-finned fish, comprising mostly small, freshwater fishes.

Many popular aquarium fish, such as killifish and live-bearers, are included.

They are closely related to the Atheriniformes and are occasionally included with them. A colloquial term for the order as a whole is toothcarps, though they are not actually close relatives of the true carps – the latter belong to the superorder Ostariophysi, while the toothcarps are Acanthopterygii.

The families of Cyprinodontiformes can be informally divided into three groups based on reproductive strategy:

• viviparous
• ovoviviparous (all species give live birth),
• oviparous (all species are egg-laying).

The live-bearing groups differ in whether the young are carried to term within (ovoviviparous) or without (viviparous) an enclosing eggshell. Phylogenetically however, one of the two suborders – the Aplocheiloidei – contains oviparous species exclusively, as do two of the four superfamilies of the other suborder (the Cyprinodontoidea and Valencioidea of the Cyprinodontoidei). Vivipary and ovovivipary have evolved independently from oviparous ancestors, the latter possibly twice.