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The crocodile exoskeleton consists of the protective dermal and epidermal components of the integumentary system in animals of the order Crocodilia. It is a form of armour. ==Structure and anatomy== The epidermal exoskeleton of the alligator consists of oblong horny scales, arranged in transverse rows; the long axes of the scales are parallel to that of the body. On the tail, except along the mid-dorsal line, and on the ventral side of the trunk and head these scales are very regular in outline and arrangement; on the sides of the head and trunk and on the legs they are much smaller and less regularly arranged, while along the mid-dorsal line of the tail, especially in its posterior half, they are elevated into tall keels that give the tail a large surface area for swimming. The first three digits of both manus (fore foot) and pes (hind foot) are armed with horny claws, which also belong to the epidermal part of the exoskeleton. The dermal exoskeleton consists of bony scutes that underlie the epidermal scales of the dorsal surface of the trunk and anterior part of the tail. The overlying scales, except in very young animals, are always rubbed off, so that the bony scales are exposed. The ventral or inner surface of the scutes is flat, while the outer surface is strongly keeled and in old animals is often rough and pitted. The plates are nearly square in outline and are closely joined together in most places. The scutes are grouped in two fairly distinct areas known as the nuchal and the dorsal shields. The former lies just back of the head, in the region of the fore legs, and consists of four larger and a number of smaller plates. The latter, or dorsal shield, extends over the back in fairly regular longitudinal rows and quite regular transverse rows. At the widest part of the trunk there are six or eight of these scutes in one transverse row. They become smaller towards the tail. The teeth are exoskeletal structures, partly of ectodermal, partly of dermal origin. They are conical in shape, without roots, and are replaced when lost. They will be described in connection with the skull. Musk glands, said by Gadow〔Gadow 1923.〕 to be present in all Crocodilia, are found in both sexes and are derivations of the skin. One pair, each of which may be as large as a walnut, is found on the lower side of the head, one on the inside of each half of the mandible. The other pair is inside of the lips of the cloaca. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Crocodilian armor」の詳細全文を読む スポンサード リンク
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