Osteoglossiformes (Greek: "bony tongues") is a relatively primitive

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

that contains two sub-orders, the

Osteoglossoidei Osteoglossoidei are a suborder of the order Osteoglossiformes (Latin: "bony tongues") that contains the butterflyfish, the arowanas and bonytongue Arapaiminae is a subfamily of freshwater osteoglossiform (bony-tongued) fishes belonging to the ...

and the

Notopteroidei Notopteroidei is a suborder of the order Osteoglossiformes that contains the extant families Gymnarchidae (aba), Notopteridae (feather backs and knifefish) and Mormyridae The Mormyridae, sometimes called "elephantfish" (more properly freshwat ...

. All of at least 245 living species inhabit freshwater. They are found in South America, Africa, Australia and southern Asia, having first evolved in

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

before that continent broke up. In 2008 several new species of

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

osteoglossiforms was described from the Danish

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

Fur Formation The Fur Formation is a marine geological formation of Ypresian (Lower Eocene Epoch, c. 56.0-54.5 Ma) age which crops out in the Limfjord region of Denmark from Silstrup via Mors and Fur to Ertebølle, and can be seen in many cliffs and quarries in ...

dramatically increases the diversity of this group. This implies that the Osteoglossomorpha is not a primary freshwater fish group with the osteoglossiforms having a typical

distribution. The

Gymnarchidae ''Gymnarchus niloticus'' – commonly known as the ''aba'', ''aba aba'', frankfish, freshwater rat-tail, ''poisson-cheval'', or African knifefish – is an electric fish, and the only species in the genus ''Gymnarchus'' and the family Gymnarchid ...

(the only species being ''

Gymnarchus niloticus ''Gymnarchus niloticus'' – commonly known as the ''aba'', ''aba aba'', frankfish, freshwater rat-tail, ''poisson-cheval'', or African knifefish – is an electric fish, and the only species in the genus ''Gymnarchus'' and the family Gymnarchid ...

'', the African knifefish) and the

Mormyridae The Mormyridae, sometimes called "elephantfish" (more properly freshwater elephantfish), are a Mormyridae (superfamily) , family of Electric fish , weakly electric freshwater fish in the order Osteoglossiformes native to Africa. It is by far the ...

are

weakly electric fish An electric fish is any fish that can generate electric fields. Most electric fish are also electroreceptive, meaning that they can sense electric fields. The only exception is the stargazer family. Electric fish, although a small minority, in ...

able to sense their prey using electric fields. The mooneyes (

Hiodontidae Hiodontidae, commonly called mooneyes, is a family of ray-finned fish with a single included genus ''Hiodon''. The genus comprise two living species native to North America and three to five extinct species recorded from Paleocene to Eocene age ...

) are often classified here, but may also be placed in a separate order,

Hiodontiformes Hiodontiformes is an order of ray-finned fish consisting of the two living species of the mooneye family, Hiodontidae, and three extinct genera. These are traditionally classified within the order Osteoglossiformes, a placement some authorit ...

. Members of the order are notable for having toothed or bony tongues, and for having the forward part of the

gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syste ...

pass to the left of the

oesophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...

and

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

(for all other fish it passes to the right). In other respects, osteoglossiform fishes vary considerably in size and form; the smallest is '' Pollimyrus castelnaui'', at just long, while the largest, the

arapaima The arapaima, pirarucu, or paiche is any large species of bonytongue in the genus ''Arapaima'' native to the Amazon and Essequibo basins of South America. ''Arapaima'' is the type genus of the subfamily Arapaiminae within the family Osteoglossi ...

(''Arapaima gigas''), reaches as much as .

Phylogeny

Phylogeny based on the following works:Sullivan, J. P., Lavoué S., & Hopkins C. D. (2000): ''Molecular systematics of the African electric fishes (Mormyroidea: Teleostei) and a model for the evolution of their electric organs.'' Journal of Experimental Biology. 203, 665-683
PDF

References

External links

*

* Li, Guo-Qing and Wilson, Mark V. H. 1998. Osteoglossomorpha. Bonytongues. Version 6 October 1998

in The

Tree of Life Web Project The Tree of Life Web Project is an Internet project providing information about the diversity and phylogeny of life on Earth. This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The site h ...

* {{Taxonbar, from=Q48407 Extant Late Jurassic first appearances Ray-finned fish orders Taxa named by Lev Berg