![]() ![]() Microstructures can include the scutes mentioned prior or the ribs found internally of the shell. Shell shape allows the animal to escape predatory situations. The shape of the shell is from its evolutionary process, which caused many microstructures to appear to aid survival and motion. A thicker epidermis allows a higher stress force to be experienced without permanent deformation or critical failure of the shell. The epidermis layer is apparent in both sections of the shell, carapace, and plastron, and is thicker in critical areas. Even with such a small thickness, the epidermis allows the deformation the shell can experience and provides the shell more support. In an international study, the layer can be as thick as two to four cells. This layer is important to the strength of the shell surrounding it. In the shell there is a turtle's epidermis layer. On the carapace are the sutures into which they insert, known as the Bridge carapace suture. The anterior bridge strut and posterior bridge strut are part of the plastron. This is not the case in Cryptodires which have a floating pelvis. In Pleurodires the posterior pelvis is also part of the carapace, fully fused with it. The actual suture between the bridge and the plastron is called the anterior bridge strut. These are joined by an area called the bridge. The ventral surface is called the plastron. Some of those bones that make the top of the shell, carapace, evolved from the scapula rami of the clavicles along with the dorsal and superficial migration of the cleithra. ![]() The turtle shell is made up of numerous bony elements, generally named after similar bones in other vertebrates, and a series of keratinous scutes which are also uniquely named. ![]() Pe=Peripheral, P1=Pleural 1, BCS=Bridge Carapace Suture Shell nomenclature Internal anterior carapace of Elseya dentata. The shell of the hawksbill turtle, among other species, has been used as a material for a wide range of small decorative and practical items since antiquity, but is normally referred to as tortoiseshell. Hence understanding the shell structure in living species provides comparable material with fossils. The turtle's shell is an important study, not just because of the apparent protection it provides for the animal but also as an identification tool, in particular with fossils, as the shell is one of the likely parts of a turtle to survive fossilization. The bone of the shell consists of both skeletal and dermal bone, showing that the complete enclosure of the shell likely evolved by including dermal armor into the rib cage. It is constructed of modified bony elements such as the ribs, parts of the pelvis and other bones found in most reptiles. The turtle shell is a shield for the ventral and dorsal parts of turtles (the order Testudines), completely enclosing all the vital organs of the turtle and in some cases even the head. Scutes (left) and skeletal components (right) of a turtle's plastron Pleurodires have an extra scute known as the intergular. ![]()
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