''Tomeurus gracilis'' is a species of

poeciliid The Poeciliidae are a family of freshwater fishes of the order Cyprinodontiformes, the tooth-carps, and include well-known live-bearing aquarium fish, such as the guppy, molly, platy, and swordtail. The original distribution of the family wa ...

fish native to

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...

, in Brazil, Surinam and Venezuela. This species grows to a length of TL. It is the only known member of its

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

. This species is classified in the

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English is in the discipline of anthropology. This definition is contested, in part due to confl ...

Cnesterodontini in the 5th edition of

Fishes of the World ''Fishes of the World'' by the American Ichthyology, ichthyologist Joseph S. Nelson (1937–2011) is a standard reference for fish systematics. Now in its fifth edition (2016), the work is a comprehensive overview of the diversity and classificat ...

. but other workers place it in its own tribe, the Tomeurini. This is a sociable fish which lives in small schools consisting of several dozens of fishes. It is found in muddy creeks or along the sandy-muddy edges of shallow estuaries. It has been observed remaining still just below the surface but it prefers to hide beneath aquatic plants. Fertilisation is internal and, uniquely among the Poeciliinae, the females may then lay eggs placing them individually onto aquatic plants. They can also be facultively

ovoviviparous Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop insi ...

References

Poeciliidae Fish of South America Taxa named by Carl H. Eigenmann Ray-finned fish genera Monotypic freshwater fish genera {{Cyprinodontiformes-stub