Cyprinodontiformes

Cyprinodontiformes is an order of mostly small ray-finned fishes that includes killifishes, livebearers, and pupfishes. Many species inhabit fresh water, and some tolerate highly variable or extreme environments.

Atherinomorpha: A group of ray-finned fishes that includes silversides, halfbeaks, and Cyprinodontiformes. Cyprinodontiformes is commonly placed within this broader grouping.
Internal fertilization: Fertilization in which sperm meets an egg inside the female reproductive tract. It occurs in the livebearing lineages of Cyprinodontiformes.
Zebrafish: A small freshwater fish widely used in developmental and genetic research; it belongs to Cypriniformes. It is a familiar research fish often confused with cyprinodontiform models, but belongs to another order.
Cypriniformes: An order of freshwater ray-finned fishes that includes carps, minnows, and loaches. The similar name masks a separate order with very different major lineages.
Fish classification: The scientific organization of fishes into evolutionary groups and named taxa. Cyprinodontiform relationships and family boundaries are revised as evidence accumulates.
Killifish: A common name for small egg-laying fishes in several cyprinodontiform families. Killifishes make up much of the order's diversity.
Ovoviviparity: Reproduction in which eggs develop inside the parent and hatch before or shortly after release. This reproductive mode describes many cyprinodontiform livebearers.
Medaka: A small East Asian ricefish used in genetics and developmental biology. Medaka is a prominent model within the order.
Beloniformes: An order of ray-finned fishes that includes needlefishes, flyingfishes, and ricefishes. It is a neighboring fish order that also contains small, slender species.
Molecular phylogenetics: The reconstruction of evolutionary relationships using DNA or protein sequences. Genetic analyses help resolve deep branching patterns within the order.

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