The tortoise's shell is a living structure composed of a carapace and a plastron joined laterally by bony bridges. It is made up of osteodermal bone plates covered with keratinized epidermal and not superimposed scales. The spine and ribs are welded to the carapace. The bony structures connecting the anterior and posterior limbs to the spine are integral with the shell. Only the reptile's neck, skull, four limbs, and tail can move.