Family of small, livebearing freshwater fishes with current taxonomic classification:
Superorder: Acanthopterygii (spiny-rayed fishes)
Order: Atheriniformes
Family: Poeciliidae
This family is commonly called the livebearing toothcarp, in contrast with the egg-laying toothcarp (or killifish). They are native to the Americas. Livebearers appeared late in the evolutionary process, about 44-38 million years ago during the Oligoscene and Miocene periods. They have an advantage over the egglaying fish in that the young can hide from predators immediately after birth. For this reason, livebearers don't need to be as prolific as egglayers; they commonly produce only 20-40 fry although some species may produce as many as 150.
Poeciliidae includes some of the most common aquarium fish:
as well as some not-so-commonly kept fish, such as
Gambusia.