# Tonguefish

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**Tonguefishes** are [flatfish](/source/Flatfish) in the [family](/source/Family_(taxonomy)) **Cynoglossidae**. They are distinguished by the presence of a long hook on the snout overhanging the mouth, and the absence of pectoral fins. Their eyes are both on the left side of their bodies, which also lack a pelvic fin.[1] This family has three [genera](/source/Genera) with a total of more than 140 species. The largest reaches a length of 66 cm (26 in), though most species only reach half that size or less.[2][3][4] They are found in [tropical](/source/Tropical) and [subtropical](/source/Subtropical) oceans, mainly in shallow waters and [estuaries](/source/Estuary), though some species are found in deep [sea floors](/source/Sea_floor),[5] and even a few in [rivers](/source/River).

*[Symphurus thermophilus](/source/Symphurus_thermophilus)* lives congregating around "ponds" of [sulphur](/source/Sulphur) at [hydrothermal vents](/source/Hydrothermal_vent) on the seafloor. No other flatfish is known from hydrothermal vents.[6] Scientists are unsure of the mechanism that allows the fish to survive and even thrive in such a hostile environment.[7]

## See also

- [List of fish families](/source/List_of_fish_families)

## References

1. *Encyclopedia of Fishes*. San Diego: Academic Press. 1998. p. 225. ISBN 0-12-547665-5.

1. Munroe, Thomas A. & Marsh, Barnaby N. (1997). ["Taxonomic status of three nominal species of Indo-Pacific symphurine tonguefishes (Symphurus: Cynoglossidae: Pleuronectiformes)"](https://www.researchgate.net/publication/227310648). *Ichthyological Research*. **44** (2–3): 189–200. [doi:10.1007/BF02678697](https://doi.org/10.1007/BF02678697). [S2CID 46661658](https://api.semanticscholar.org/CorpusID:46661658). Retrieved 2015-11-01.

1. Munroe, Thomas A. & Hashimoto, Jun (1 August 2008). ["A new Western Pacific Tonguefish (Pleuronectiformes: Cynoglossidae): The first Pleuronectiform discovered at active Hydrothermal Vents"](http://www.mapress.com/zootaxa/2008/f/zt01839p059.pdf). *[Zootaxa](/source/Zootaxa)*. **1839**: 43–59. [doi:10.11646/zootaxa.1839.1.2](https://doi.org/10.11646/zootaxa.1839.1.2)

1. Amos, Jonathan (14 December 2006). ["Fish dance on sulphur cauldrons"](https://news.bbc.co.uk/1/hi/sci/tech/6212716.stm). BBC News. Retrieved 25 May 2010.

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