Splitfins are a family, Goodeidae, of teleost fish endemic to Mexico and some areas of the United States. This family contains about 50 species within 18 genera.[1][2] The family is named after ichthyologist George Brown Goode.

Xenotoca eiseni
Redtail splitfin, Xenotoca eiseni
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cyprinodontiformes
Suborder: Cyprinodontoidei
Family: Goodeidae
D. S. Jordan, 1923

See text for genera and species.


The family is divided into two subfamilies, the Goodeinae and the Empetrichthyinae. The Goodeinae are endemic to shallow freshwater habitats in Mexico, particularly along the Mesa Central area (especially the Lerma River basin, smaller rivers directly south of it and inland to around the Valley of Mexico region), with some species found in brackish fringes at the Pacific coast, and north to central Durango, central Sinaloa and north San Luis Potosí. There are about 45 species of Goodeinae in 16 genera (some list 2 additional genera). The Empetrichthyinae are found in the southwestern Great Basin in Nevada, the United States, and contains 4 species in 2 genera.[3]

Physical information

The name "splitfin" comes from the fact that, in the male fish, the anterior rays of the anal fin are partly separated from rest of the fin. Splitfins can be up to 20 cm (8 in) in length, though most species are much smaller, around 5 cm (2 in). Goodeid fish have internal fertilisation, with males positioning themselves with a flexible part of the front anal fin, separated by a notch, which makes up the andropodium. Embryos hatch out of the egg within the ovarian follicle, and possess trophotaeniae, ribbon-like structures that emerge from the cloaca in front of the anal fin, on the ventral surface of the juvenile. These allow the absorption of nutrients within the ovary (matrotrophy), and are shed by juveniles shortly after birth. Female goodeids do not store sperm, and so a copulation event must precede each pregnancy.[4]

Conservation status

In recent years there has been a significant reduction in the range and size of Goodeid populations in this region, mainly due to anthropogenic disturbances, such as pollution, eutrophication, habitat modification and desiccation; recent estimates put habitat loss at 80% compared to historic ranges.[5] The low economic importance of Goodeid fish to Mexican fisheries and industry has led to this family being largely ignored by conservation efforts, but their small size and the dedication of a small number of aquaria hobbyists has led to a recent increase in the amount of research dedicated to the family. These investigations have highlighted the implications for conservation efforts concerning other global freshwater ichthyofauna.

Several species are threatened or extinct according to the IUCN[6] and the U.S. Fish and Wildlife Service[7]

Life cycle and evolution

The majority of Goodeid fish are viviparous, typically giving birth to live young. The family includes a number of popular aquarium fish, for example the redtail splitfin Xenotoca eiseni. Recent phylogenetic studies have put the age of this family at approximately 16.5 million years, with the majority of divergence occurring in the Miocene period. The speciosity of this family can be attributed to historical volcanic and geological disturbance in this region, which created suitable conditions for allopatric speciation of the fish.[2]


The following genera are included in Goodeidae:[1]

Subfamily Empetrichthyinae – springfishes and poolfishes

Subfamily Goodeinae – typical goodeids and splitfins


  1. ^ a b Froese, Rainer, and Daniel Pauly, eds. (2006). "Goodeidae" in FishBase. February 2006 version.
  2. ^ a b Webb, S.A.; Graves, J.A.; Macías-Garcia, C.; Magurran, A.E.; O'Foighil, D. & Ritchie, M.G. (2004). "Molecular phylogeny of the livebearing Goodeidae (Cyprinodontiformes)". Molecular Phylogenetics and Evolution. 30 (3): 527–544. doi:10.1016/S1055-7903(03)00257-4. PMID 15012937.
  3. ^ Foster, K.L.; K.R. Piller (2018). "Disentangling the drivers of diversification in an imperiled group of freshwater fishes (Cyprinodontiformes: Goodeidae)". BMC Evolutionary Biology. 18 (116). doi:10.1186/s12862-018-1220-3.
  4. ^ Ellenberg, G. (2005) Goodeiden [Online]. Available:
  5. ^ De la Vega-Salazar, M. Y. & Macías-García, C. (In press) Principal Factors in the decline of the Mexican endemic viviparous fishes (Goodeinae: Goodeidae). Ch. 33 in: H. J. Grier & M. C. Uribe (Eds.) Viviparous Fishes. Proceedings of I and II International Symposia. New Life Publications, Homestead FL, USA.
  6. ^ IUCN Red List -
  7. ^ Fish and Wildlife Service, Proposed rules: Pahrump poolfish; withdrawn.

Allodontichthys is a genus of splitfins, endemic to the Tuxpan (Coahuayana), Armería and Ameca river basins in Colima and Jalisco, west–central Mexico.

Alloophorus robustus

The bulldog goodeid (Alloophorus robustus) is a species of goodeid. It is endemic to stagnant and slow-flowing waters in the Lerma–Chapala, Presa de San Juanico and Balsas basins in west-central and southwestern Mexico. Despite its relatively wide range, it is generally uncommon. This is possibly the most predatory goodeid, it feeding on other fish, crayfish, insects and other invertebrates. At up to at least 14.3 cm (5.6 in) in standard length, this is likely the second-largest goodeid, after Goodea atripinnis.

Ash Meadows killifish

The Ash Meadows killifish (Empetrichthys merriami) was first documented by C. H. Gilbert in 1893 and historically occupied numerous springs near Ash Meadows, Nye County, Nevada, United States. This species was last seen in 1948 and is believed to have gone extinct in the early 1950s, likely as a result of habitat alteration and competition with and predation by introduced crayfish Procambarus clarkii, mosquitofish (Gambusia affinis), black mollies (Poecilia sphenops), and bullfrogs (Rana catesbeiana).The common name of the genus Empetrichthys has since been changed from killifish to poolfish.

Butterfly splitfin

The butterfly splitfin or butterfly goodeid, Ameca splendens, is a bony fish from the monotypic genus Ameca

of the splitfin family (Goodeidae). It was formerly found throughout the Ameca River drainage in Mexico; the type locality is Rio Teuchitlán in the vicinity of Teuchitlán, Jalisco. The species was only ever found in an area about 10 miles (15 km) in diameter.Today, the species is rated as extinct in the wild by the IUCN, though this assessment is obsolete: a remnant population has been found to persist in El Rincón waterpark near the town of Ameca. Possibly, it also exists in a feral state in the United States; individuals apparently derived from escaped or introduced captive stock were met with in southeastern Nevada. For some time, it was a popular fish among aquarists, but hobbyist stocks have declined recently, placing its survival in jeopardy.


Characodon is a genus of splitfins endemic to north–central Mexico. Two of the species are highly threatened and restricted to pools, ponds and springs in the upper San Pedro Mezquital River basin in Durango. The third species, C. garmani, was restricted to springs near Parras in Coahuila, but it became extinct when they dried out.


Crenichthys is a genus of fish in the family Goodeidae, the splitfins. This small genus consists of two species which are both endemic to Nevada in the United States. They occur in small populations in isolated warm springs. Fish of this genus are known commonly as springfish.

Distinctive characteristics include the loss of the pelvic fins, a relatively large anal fin and one or two rows of black spots along each side.


Empetrichthys is a genus of splitfins endemic to the state of Nevada in the United States.


Fundulus is a genus of ray-finned fishes in the superfamily Funduloidea, family Fundulidae (of which it is the type genus). It belongs to the order of toothcarps (Cyprinodontiformes), and therein the large suborder Cyprinodontoidei. Most of its closest living relatives are egg-laying, with the notable exception of the splitfin livebearers (Goodeidae).

They are usually smallish; most species reaching a length of at most 4 in (10 cm) when fully grown. However, a few larger species exist, with the giant killifish (F. grandissimus) and the northern studfish (F. catenatus) growing to twice the genus' average size.

Many of the 40-odd species are commonly known by the highly ambiguous name "killifish" (the general term for egg-laying toothcarps), or the somewhat less ambiguous "topminnow" (a catch-all term for Fundulidae). "Studfish" is a quite unequivocal vernacular name applied to some other Fundulus species; it is not usually used to refer to the genus as a whole, however.

Golden skiffia

Skiffia francesae, the golden skiffia or tiro dorado, is a species of splitfin endemic to the Rio Teuchitlán, a tributary of Río Ameca in western Mexico. It is extinct in the wild, but has been maintained in aquaria and the aquarium hobbyist trade.

Hubbsina turneri

The Highland Splitfin (Hubbsina turneri) is a species of splitfin endemic to Mexico where it is found in the Lerma River basin. This species grows to a length of 5 centimetres (2.0 in) TL. It is the only known member of its genus.


Ilyodon is a genus of splitfins found in the Pacific slope river basins of Balsas, Tuxpan (Coahuayana), Purificación, Chacala (Marabasco), Armería and Ameca in western Mexico.

Ilyodon whitei

The Balsas splitfin (Ilyodon whitei) is a species of fish in the family Goodeidae. It is endemic to Mexico.

List of aquarium fish by scientific name

This page lists all fish commonly kept in aquariums and ponds.

Raycraft Ranch killifish

The Raycraft Ranch killifish or Raycraft poolfish, Empetrichthys latos concavus, was first described in 1948. It is extinct.

Redtail splitfin

The redtail splitfin, or redtail goodeid, (Xenotoca eiseni) is a species of goodeid fish from the family Goodeidae and subfamily Goodeinae. Like other members of Goodeinae, the redtail splitfin is native to Mexico and a livebearer. However, the goodeid mating system differs in several ways from the more common livebearing fish from the family Poeciliidae that includes guppies and swordtails. While no goodeid species is a very popular aquarium fish, the redtail splitfin is one of the most popular. Only the male has the red-orange tail for which it is named.

White River springfish

The White River springfish (Crenichthys baileyi) is a species of fish in the family Goodeidae, the splitfins. It is a rare species of the Great Basin of western United States, where it is endemic to isolated warm springs in the White River drainage of eastern Nevada.Each side has two rows of dark blotches. The pelvic fins are entirely absent, while the anal fin is large, with 14 rays. The dorsal fin is set far back on the body, just above the anal fin, and is somewhat smaller than the anal fin, with 11 rays.

Xenotaenia resolanae

Xenotaenia resolanae, the leopard splitfin, is a species of splitfin endemic to west–central Mexico where it is found in the Purificación and Marabasco River basins in Jalisco and Colima. This species grows to a length of 5 centimetres (2.0 in) TL. It is found in the aquarium trade and is the only known species in its genus.


Xenotoca is a genus of fish in the family Goodeidae from Mexico, where found in a wide range of habitats, from rivers and creeks to pools and lakes, in the Lerma–Grande de Santiago, Panuco, Cuitzeo and other basins of the Mesa Central. While no goodeid is a very common aquarium fish, the redtail splitfin (X. eiseni), is one of the most common aquarium goodeids. Its relatively bright colors offset its reputation for being aggressive towards tankmates, occasionally even killing them. Similarly to that species, two species described in 2016 have males with red-orange tails, but this feature is not shared by the remaining members of the genus. The Xenotoca species are small, reaching up to 9 cm (4 in) in standard length.

Zoogoneticus tequila

Zoogoneticus tequila, Tequila splitfin or simply Tequila fish, is a species of goodeid fish (family Goodeidae) from Mexico. The specific epithet, tequila, derives from the Tequila Volcano, which looms near the type locality.

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