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ScalesNomenclature
This part of the article provides a photographic guide cum glossary of scale names on a snake's head and body for easy and convenient identification by the reader, with annotated photographs of Buff-striped Keelback Amphiesma stolata (a common grass-snake of South Asia) for following the text.
Head scales
Nomenclature of scales (underside view of head)
Identification of scales is most conveniently begun with reference to the nostril which is easily identified on the snake. There are two scales enclosing the nostril which are called the NASALs. The outer nasal (near the snout) is called the PRENASAL. The inner nasal (near the eye) is called the POSTNASAL. Along the top of the snout connecting the nasals on both sides of the head are scales called INTERNASALs. Between the two prenasals is a scale at the tip of the snout. This is called the ROSTRAL scale.
The scales around the eye are called CIRCUMORBITAL scales and are named as ocular scales but with appropriate prefix. The OCULAR SCALE proper is a transparent scale covering the eye. The ocular scale is also called Spectacle, Brille or Eyecap.
The circumorbital scales towards the snout or the front are called PREOCULAR scales, those towards the rear are called POSTOCULAR scales and those towards the upper or dorsal side are called as SUPRAOCULAR scales. Circumorbital scales toawrds the venral or lower side, if any, are called as SUBOCULAR scales.
Between the preocular and the postnasal scales are the LOREAL scales. The scales along the lips of the snake are called as LABIALs. Those on the upper lip are called SUPRALABIALs while those on the lower labial are called INFRALABIALs.
Between the eyeballs on top of the head, adjacent to the supraoculars are the FRONTAL scales. The PREFRONTAL scales are the scales connected to the frontals towards the tip of the snout which are in contact with the rostrals.
The back of the top of the head has scales connected to the frontal scales called as the PARIETAL scales. At the sides of the back of the head are scales called TEMPORAL scales.
On the underside of the head, a snake has an anterior scale called as the MENTAL scale. Connected to the mental scales and all along the lower jaws are the INFRALABIALs. Along the lower jaw connected to infralabials are a pair of shields called the ANTERIOR CHIN SHIELDs. Next to the anterior chin shields, further back along the jaw are another pair of shields called the POSTERIOR CHIN SHIELDs.
Scales on the body
Enlarged vertebral scales of Banded Krait Bungarus fasciatus The scales on the body of the snake are called the DORSAL or COSTAL scales. Sometimes there is a special row of large scales along the top of the back of the snake, i.e, the uppermost row, called the VERTEBRAL scales. The enlarged scales on the belly of the snake are called VENTRAL scales or GASTROSTEGEs.
In "advanced" (Caenophidian) snakes, the broad belly scales and rows of dorsal scales correspond to the vertebrae, allowing scientists to count the vertebrae without dissection.
Tail scales
Nomenclature of scales (underside view of body) At the end of the ventral scales of the snake is an anal plate which protects the opening to the cloaca (a shared opening for waste and reproductive material to pass) on the underside near the tail. This ANAL scale may be single or divided into a pair. The part of the body beyond the anal scale is considered to be the tail.
Sometimes snakes have enlarged scales, either single or paired, under the tail; these are called SUBCAUDALs or UROSTEGEs. These subcaudals may be smooth or keeled as in Bitis arietans somalica. The end of the tail may simply taper into a tip (as in the case of most snakes), it may form a spine (as in Acanthophis), end in a bony spur (as in Lachesis), a rattle (as in Crotalus), or a rudder as seen in many sea snakes.
The rattlesnake tail is made up of a series of loosely linked, interlocking chambers that when shaken, vibrate against one another to create the warning signal of a rattlesnake. Only the bottom button is firmly attached to the tip of the tail.
Sources. Details for this section have been sourced from scale diagrams in Malcolm Smith. Details of scales of Buff-striped Keelback have been taken from Daniels.
Arrangement of scales
Snake have imbricate scales, overlapping like the tiles on a roof. [20] Snakes have rows of scales along the whole or part of their length and also many other specialised scales, either singly or in pairs, occurring on the head and other regions of the body.
The dorsal scales on the snake's body are arranged in rows along the length of their bodies. Adjacent rows are diagonally offset from each other. Most snakes have an odd number of rows across the body though certain species have an even number of rows e.g. Zaocis spp. [2] In the case of some aquatic and marine snakes, the scales are granular and the rows cannot be counted .
The number of rows range from ten in Tiger Ratsnake Spilotes pullatus; thirteen in Dryocalamus, Liopeltis, Calamaria and Asian coral snakes of genus Calliophis; 65 to 75 in Python; 74 to 93 in Kolpophis and 130 to 150 in Acrochordus. The majority of the largest family of snakes, the Colubridae have 15, 17 or 19 rows of scales. The maximum number of rows are in mid-body and they reduce in count towards the head and on the tail.
Glossary of scales
Nomenclature of scales (side view of head)
A line diagram from G.A. Boulenger's Fauna of British India (1890)illustrating the terminology of shields on the head of a snake
Other pertinent terms
Cultural significance
The highly periodic cross-hatch or grid patterns on snakeskin appeal to people's aesthetics. Snakeskin is used to manufacture of many leather articles including fashionable accessories. The use of snakeskin has endangered snake populations and resulted in international restrictions in trade of certain snake species and populations in the form of CITES provisions. Animal lovers in many countries propagate the use of artificial snakeskin instead, which are easily produced from embossed leather, patterned fabric, plastics and other materials.
Snake scales have inspired dread and awe in humans from pre-historic times. Patterns in art prevalent to those times and later on may be ascribed to the visual influence of snakes, some of which, such as the Gaboon Viper, can both repel and fascinate the human mind. Studies of fear imagery and psychological arousal indicate that snake scales are a vital component of snake imagery. Snake scales also appear to have affected Islamic art in the form of tessallated mosaic patterns which show great similarity to snake-scale patterns.
A snake scale was portrayed as a clue in the 1982 sci-fi cum film noir called 'Blade Runner'. Snake scales occur as a motif regularly in computer action games. Snake scales also figure in popular fiction, such as the Harry Potter series (as a raw material for concocting potions), and also in teen fiction
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