Reptile scale

Reptile skin is covered with scutes or scales which, along with many other characteristics, distinguish reptiles from animals of other classes. Scales are made of alpha and beta keratin and are formed from the epidermis (contrary to fish, in which the scales are formed from the dermis). They may be ossified or tubercular, as in the case of lizards, or modified elaborately, as in the case of snakes.

Lizard scales vary in form from tubercular to platelike, or imbricate (overlapping). These scales, which on the surface are composed of horny (keratinized) epidermis, may have bony plates underlying them; these plates are called osteoderms. Lizard scales may differ strongly in form on different parts of the lizard and are often of use in taxonomically differentiating species.

Snakes are entirely covered with scales or scutes of various shapes and sizes. Scales protect the body of the snake, aid it in locomotion, allow moisture to be retained within and give simple or complex colouration patterns which help in camouflage and anti-predator display. In some snakes, scales have been modified over time to serve other functions such as 'eyelash' fringes, and protective covers for the eyes with the most distinctive modification being the rattle of the North American rattlesnakes. Snakes periodically moult their scaly skins and acquire new ones. This permits replacement of old worn out skin, disposal of parasites and is thought to allow the snake to grow. The shape and arrangement of scales is used to identify snake species.

The shape and number of scales on the head, back and belly are characteristic to family, genus and species. Scales have a nomenclature analogous to the position on the body. 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.

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