Tonguefishes are flatfish in the familyCynoglossidae. 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]
They are found in tropical and subtropical oceans, mainly in shallow waters and estuaries, though some species are found in deep sea floors,[6] and even a few in rivers.
Symphurus thermophilus lives congregating around "ponds" of sulphurathydrothermal vents on the seafloor. No other flatfish is known from hydrothermal vents.[7] Scientists are unsure of the mechanism that allows the fish to survive and even thrive in such a hostile environment.[8]
^Froese, Rainer, and Daniel Pauly, eds. (2012). "Cynoglossidae"inFishBase. October 2012 version.
^Chapleau, Francois; Amaoka, Kunio (1998). Paxton, J. R.; Eschmeyer, W. N. (eds.). Encyclopedia of Fishes. San Diego: Academic Press. p. 225. ISBN0-12-547665-5.
