The Hemiodontidae are a small

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

of freshwater

characin Characiformes is an order of ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known piranha and tetras.; Buckup P.A.: "Relationsh ...

s found in northern South America, south to the Paraná-

Paraguay Paraguay (; ), officially the Republic of Paraguay ( es, República del Paraguay, links=no; gn, Tavakuairetã Paraguái, links=si), is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to th ...

Basin. The larger species are popular food fish. Hemiodontids have a streamlined body shape; many are fast-swimming, and are able to leap out of the water to escape predators. The adults of all species except ''

Micromischodus sugillatus ''Micromischodus sugillatus'' is a species of halftooth endemic to the Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or a ...

'' have no teeth on their lower jaws. Most species have a round spot on the side of the midbody and a stripe along the lower lobe of the

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as s ...

. The largest hemiodontids are around in length.

Genera

The family has around 29 known

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

, as well as several undescribed species, in five

genera 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 ...

: *''

Anodus ''Anodus'' is a genus of halftooths from tropical South America. There are currently two species in this genus. Species * '' Anodus elongatus'' Agassiz, 1829 * '' Anodus orinocensis'' (Steindachner Franz Steindachner (11 November 1834 in Vi ...

'' *''

Argonectes ''Argonectes'' is a genus of halftooths from tropical 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 th ...

'' *''

Bivibranchia ''Bivibranchia'' is a genus of halftooths from tropical South America, with five recognized species: * '' Bivibranchia bimaculata'' Vari, 1985 * '' Bivibranchia fowleri'' (Steindachner, 1908) * '' Bivibranchia notata'' Vari & Goulding, 1985 * ...

'' *''

Hemiodus ''Hemiodus'' is a genus of halftooths from South America with the greatest species richness in the Amazon Basin, but also found in the Orinoco, Essequibo, Paraná–Paraguay and Parnaíba River basins. Depending on the species involved, these ...

'' *'' Micromischodus''

References

*Nelson, Joseph S. (2006). ''

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 ...

''. John Wiley & Sons, Inc. Fish of South America {{Characiformes-stub