The Hemiodontidae are a small

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

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 Paraná, Paranã or Parana may refer to: Geology * Paraná Basin, a sedimentary basin in South America Places In Argentina *Paraná, Entre Ríos, a city * Paraná Department, a part of Entre Ríos Province In Brazil *Paraná (state), a state ...

Paraguay Paraguay, officially the Republic of Paraguay, is a landlocked country in South America. It is bordered by Argentina to the Argentina–Paraguay border, south and southwest, Brazil to the Brazil–Paraguay border, east and northeast, and Boli ...

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 tributary, tributaries. The Amazon drainage basin covers an area of about ...

'' 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 moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

. The largest hemiodontids are around in length. Fossil remains of ''

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 ...

'' are known from the

Middle Miocene The Middle Miocene is a sub-epoch of the Miocene epoch (geology), epoch made up of two Stage (stratigraphy), stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0. ...

-aged

Pebas Formation The Pebas Formation is a stratigraphic unit#Lithostratigraphic units, lithostratigraphic unit of Miocene age, found in western Amazon rainforest, Amazonia. The geological formation, formation extends over , including parts of Brazil, Peru, Ecuador ...

of Peru.

Genera

The family has around 29 known

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

, as well as several undescribed species, in five

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

: *''

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 V ...

Cuvier Jean Léopold Nicolas Frédéric, baron Cuvier (23 August 1769 – 13 May 1832), known as Georges Cuvier (; ), was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...

, 1829 *''

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 considerably smaller portion in the Northern Hemisphere. ...

'' Böhlke &

Myers Myers as a surname has several possible origins, e.g. Old French ("physician"), Old English ("mayor"), and Old Norse ("marsh"). People * Abram F. Myers (1889–after 1960), chair of the Federal Trade Commission and later general counsel and b ...

, 1956 *''

Bivibranchia ''Bivibranchia'' is a genus of halftooths from tropical South America, with five recognized species: * '' Bivibranchia bimaculata'' Vari Vari () is a southern suburb of Athens and former municipality in East Attica, Greece along the Athens co ...

'' Eigenmann, 1912 *''

Müller Müller may refer to: Companies * Müller (company), a German multinational dairy company ** Müller Milk & Ingredients, a UK subsidiary of the German company * Müller (store), a German retail chain * GMD Müller, a Swiss aerial lift manufacturi ...

, 1842 *''

Micromischodus ''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 tributary, tributaries. The Amazon drainage basin covers an area of about ...

'' Roberts, 1971

References

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

Fishes of the World ''Fishes of the World'' is a standard reference for the systematics of fishes. It was first written in 1976 by the American ichthyologist Joseph S. Nelson (1937–2011). Now in its fifth edition (2016), the work is a comprehensive overview of t ...

''. John Wiley & Sons, Inc. Fish of South America Characiformes families {{Characiformes-stub Taxa named by Pieter Bleeker