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Symphurus pusillus.jpg
Northern tonguefish, Symphurus pusillus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Pleuronectiformes
Suborder: Soleoidei
Family: Cynoglossidae
Subfamilies & Genera[1]

Subfamily Cynoglossinae


Subfamily Symphurinae


Tonguefishes are flatfishes in the family 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.[2] This family has three 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.[3][4][5]

A preserved tongue sole at a lab

They are found in tropical and subtropical oceans, mainly in shallow waters and estuaries, though a few species found in deep sea floors, and a few in rivers.

Symphurus thermophilus lives congregating around "ponds" of sulphur at hydrothermal vents 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[edit]


  1. ^ Froese, Rainer, and Daniel Pauly, eds. (2012). "Cynoglossidae" in FishBase. October 2012 version.
  2. ^ Chapleau, Francois; Amaoka, Kunio (1998). Paxton, J. R.; Eschmeyer, W. N., eds. Encyclopedia of Fishes. San Diego: Academic Press. p. 225. ISBN 0-12-547665-5. 
  3. ^ Froese, Rainer, and Daniel Pauly, eds. (2014). Species of Cynoglossus in FishBase. May 2014 version.
  4. ^ Froese, Rainer, and Daniel Pauly, eds. (2014). Species of Paraplagusia in FishBase. May 2014 version.
  5. ^ Froese, Rainer, and Daniel Pauly, eds. (2014). Species of Symphurus in FishBase. May 2014 version.
  6. ^ Munroe, Thomas A.; Hashimoto, Jun (1 August 2008). "A new Western Pacific Tonguefish (Pleuronectiformes: Cynoglossidae): The first Pleuronectiform discovered at active Hydrothermal Vents" (PDF). Zootaxa 1839: 43–59. 
  7. ^ Amos, Jonathan (14 December 2006). "Fish dance on sulphur cauldrons". BBC News. Retrieved 25 May 2010.