Keeled scales refer to

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

scales that, rather than being smooth, have a ridge down the center that may or may not extend to the tip of the scale, Campbell, J. A., Lamar, W. W. (2004). ''The Venomous Reptiles of the Western Hemisphere''. Ithaca and London: Comstock Publishing Associates. 870 pp. 1,500 plates. . making them rough to the touch. According to Street's (1979) description of European

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

s and

snake Snakes are elongated, Limbless vertebrate, limbless, carnivore, carnivorous reptiles of the suborder Serpentes . Like all other Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales. Ma ...

s, in those that have keeled scales the keels are usually stronger in male specimens and are consistently arranged according to the species of reptiles, even though many others do not have them. With European lizards, the dorsal scales are usually well keeled, while those on the flanks are more weakly keeled and those on the belly smooth. Street, D. (1979). ''The Reptiles of Northern and Central Europe''. London: B.T. Batsford Ltd. 268 pp. . Non-European lizards such as ''

Sphaerodactylus macrolepis ''Sphaerodactylus macrolepis'', also known as the big-scaled dwarf gecko or the big-scaled least gecko, is a lizard of the ''Sphaerodactylus'' genus. It was first documented in 1859 in the US Virgin Islands, specifically, St. Croix. This diurnal sp ...

'' also display keeled scales. Klauber (1997), describes how the keels on the scales of ''

Crotalus ''Crotalus'' is a genus of venomous pit vipers in the family Viperidae, known as rattlesnakes or rattlers.Albert Hazen WWright AH, Wright AA (1957). ''Handbook of Snakes of the United States and Canada''. Ithaca and London: Comstock Publishing ...

rattlesnakes Rattlesnakes are venomous snakes that form the genera ''Crotalus'' and ''Sistrurus'' of the subfamily Crotalinae (the pit vipers). All rattlesnakes are vipers. Rattlesnakes are predators that live in a wide array of habitats, hunting small anima ...

are particularly strong mid-dorsally, but gradually weaken on the lateral rows with the ventral scales being smooth. He stated that the function of the keels was uncertain, but that since they reduced shininess, and thus made it easier for the animals to conceal themselves, it afforded them an evolutionary advantage. Klauber, L. M. (1997). ''Rattlesnakes: Their Habitats, Life Histories, and Influence on Mankind''. Second Edition. First published in 1956, 1972. Berkeley: University of California Press. . In some viperines, most notably those of the genus ''

Echis ''Echis'' (common names: saw-scaled vipers, carpet vipersSpawls S, Branch B. 1995. ''The Dangerous Snakes of Africa''. Dubai: Ralph Curtis Books. Oriental Press. 192 pp. .) is a genus of vipers found in the dry regions of Africa, the Middle East ...

'', the lateral scales are not only keeled, but the keels have minute serrations. The snakes use this in a warning and threat display: the body is arranged into a series of parallel C-shaped (counterlooped) coils that they rub together continuously to produce a sizzling sound, rather like water on a hot plate. This method of making sound is called

stridulation Stridulation is the act of producing sound by rubbing together certain body parts. This behavior is mostly associated with insects, but other animals are known to do this as well, such as a number of species of fish, snakes and spiders. The mech ...

. Mallow, D., Ludwig, D., Nilson, G. (2003). ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. 359 pp. .

Gallery

Image:Hornviper_Cerastes_cerastes.jpg,

Horned desert viper ''Cerastes cerastes'', commonly known as the Saharan horned viperMallow D, Ludwig D, Nilson G. (2003). ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. . or the desert horned viper ...

(''Cerastes cerastes'') Image:Bitis arietans.jpg,

Puff adder The puff adder (''Bitis arietans'') is a viperinae, viper species found in savannahs and grasslands from Morocco and western Arabia throughout Africa except for the Sahara and rainforest regions.U.S. Navy. 1991. ''Venomous Snakes of the World'' ...

(''Bitis arietans'') Image:Viperaberus1.jpg,

Common European adder ''Vipera berus'', the common European adderMallow D, Ludwig D, Nilson G. (2003). ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. . or common European viper,Stidworthy J. (1974). ...

(''Vipera berus'') Image:Crotalus cerastes mesquite springs CA-2.jpg,

Horned rattlesnake ''Crotalus cerastes'', known as the sidewinder, horned rattlesnake or sidewinder rattlesnake,Wright AH, Wright AA. 1957. Handbook of Snakes. Comstock Publishing Associates. (7th printing, 1985). 1105 pp. . is a pit viper species belonging to the ...

(''Crotalus cerastes'') Image:Crotalus atrox Portrait 070731.jpg,

Western diamondback rattlesnake The western diamondback rattlesnake or Texas diamond-backWright AH, Wright AA. (1957). ''Handbook of Snakes''. Comstock Publishing Associates. (7th printing, 1985). . (''Crotalus atrox'') is a rattlesnake species and member of the viper family, ...

(''Crotalus atrox'') Image:Montivipera xanthina.JPG,

Ottoman viper ''Montivipera xanthina'', known as the rock viper, coastal viper, Ottoman viper,Mallow D, Ludwig D, Nilson G. 2003. ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. 359 pp. . and b ...

shows typical non-reflective appearance of reptiles with keeled scales Image:Crotalus horridus (5).jpg,

Timber rattlesnake The timber rattlesnake, canebrake rattlesnake, or banded rattlesnake (''Crotalus horridus'') Wright AH, Wright AA (1957). ''Handbook of Snakes of the United States and Canada''. Ithaca and London: Comstock Publishing Associates, a division of ...

(''Crotalus horridus'') Image:Echis carinatus head sal.jpg, ''

Echis carinatus ''Echis carinatus'', known as the saw-scaled viper,Mallow D, Ludwig D, Nilson G (2003). ''True Vipers: Natural History and Toxinology of Old World Vipers''. Malabar, Florida: Krieger Publishing Company. 359 pp. . Indian saw-scaled viper, little I ...

'' Image:Bothropoides_neuwiedi_-_Jardim_Zoológico_de_Brasília_-_DSC09973.JPG,

Bothrops neuwiedi :''Common names: Neuwied's lancehead, Silva VX da (2004). "The ''Bothrops neuwiedi'' complex". ''In'': Campbell JA, Lamar WW (2004). ''The Venomous Reptiles of the Western Hemisphere''. Ithaca and London: Comstock Publishing Associates. 870 pp. ...

(''Neuwied's lancehead'') Image:Keeled_Scales_on_skin_of_Puff_Adder_IMG_0875.JPG,

Puff Adder The puff adder (''Bitis arietans'') is a viperinae, viper species found in savannahs and grasslands from Morocco and western Arabia throughout Africa except for the Sahara and rainforest regions.U.S. Navy. 1991. ''Venomous Snakes of the World'' ...

(Bitis arietans)

References

{{Reflist Snake scales