Order Cyprinodontiformes
Suborder Cyprinodontoidei
Family Poeciliidae
Subfamily Poeciliinae
Genus Scolichthys
— Scolichthys greenwayi [Rosen, 1967]. Guatemala, Salba River. Male 3 cm, female 4 cm. The main color varies from greenish-blue to brownish-gray with a bluish-purple tint and 1-4 large black spots in the middle of the body and a central black stripe. In males, the tail and dorsal fins are transparent, bluish-yellowish with a smoky border. Males in the wild are very few compared to females, with 1 male to 10-15 females. They like to stay among plants. After 4 weeks, the female gives birth to up to 30 fry. dH 2-10°; pH 7.0-8.0; T 20-24°C.
Genus Tomeurus
— Tomeurus gracilis [Eigenmann, 1909]. Eastern Venezuela, Guyana, Suriname, Brazil. 6-8 cm. Similar in shape to Alfaro. Brownish-yellow with specks and a thin stripe in the middle of the body. Fins are transparent or yellowish. Shoaling fish, they like to stay under floating vegetation. Brackish water is required; in clean fresh water, fish contract bacterial infections, which usually lead to a fatal outcome. In terms of reproduction, the only exception in the family is Tomeurus gracilis, which spawns eggs like most fish. Fertilization is internal; a few days after fertilization, females lay eggs on aquatic plants. dH 2-10°; pH 6.8-8.0; T 24-29°C.
Genus Xenophallus
— Xenophallus umbratilis [Meek, 1912]. Synonym: Brachyrhaphis, Gambusia, Neoheterandria umbratilis, Poeciliopsis maculifer. Rivers of the Atlantic coast of Costa Rica, Nicaragua. Male 4-5 cm, female up to 6 cm. Body slender, translucent, yellowish with shiny silvery scales. The dorsal fin in males is bright yellow with a black spot, in females it is bright yellow. Males and juveniles have 5 to 10 faint black dashes on the rear half of the body, which are absent in females. When excited, males turn bright yellow, although females always look about the same. The gonopodium is asymmetrical, either right-sided or left-sided. Peaceful, very active, live in small groups. They are more sensitive to ammonia than most fish. They mature at 3-4 months. Every 4 weeks, the female gives birth to 10-20 fry measuring 8 mm. dH 10-20°; pH 7-7.5, T 24-26°C.
Alfaro cultratus, Alfaro huberi.
Genus Cnesterodon, Genus Neoheterandria, Genus Priapichthys. 
