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The scales may be ossified or tubercular, as in the case of lizards, or modified elaborately, as in the case of snakes. [1] The scales on the top of lizard and snake heads has also been called pileus, after the Latin word for cap, referring to the fact that these scales sit on the skull like a cap. [2]
Most snakes have extra broad scales on the belly, each scale covering the belly from side to side. The scales of all reptiles have an epidermal component (what one sees on the surface), but many reptiles, such as crocodilians and turtles, have osteoderms underlying the epidermal scale.
The skin is tough and leathery, and is shed (sloughed) as the animal grows. Unlike snakes which shed the skin in a single piece, lizards slough their skin in several pieces. The scales may be modified into spines for display or protection, and some species have bone osteoderms underneath the scales. [6] [7]
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 arrangement of scales is used to identify snake species. Snakes have been part and parcel of culture and religion.
Reptiles, in the traditional sense of the term, are defined as animals that have scales or scutes, lay land-based hard-shelled eggs, and possess ectothermic metabolisms. So defined, the group is paraphyletic , excluding endothermic animals like birds that are descended from early traditionally-defined reptiles.
Spotted patterning can similarly help snakes to blend into their environment. [62] The shape and number of scales on the head, back, and belly are often characteristic and used for taxonomic purposes. Scales are named mainly according to their positions on the body.
Over time, some of them evolved to have larger body sizes, and by 202 million years ago, ocean titans such as severnensis were likely the largest marine reptiles.
Reptiles, from Nouveau Larousse Illustré, 1897–1904, notice the inclusion of amphibians (below the crocodiles). In the 13th century, the category of reptile was recognized in Europe as consisting of a miscellany of egg-laying creatures, including "snakes, various fantastic monsters, lizards, assorted amphibians, and worms", as recorded by Beauvais in his Mirror of Nature. [7]