Turtle shell

A turtle shell is a bony structure formed from modified ribs and vertebrae, covered by keratinous scutes or skin. It is integrated with the skeleton rather than a removable external armor.

Carapace: The dorsal, or upper, portion of a turtle’s shell. Expanded ribs and vertebrae contribute to this upper shell, which protects the back and internal organs.
Vertebral column: The articulated series of vertebrae that supports the trunk and protects the spinal cord. Turtle vertebrae are fused with the carapace rather than remaining freely articulated there.
Odontochelys: An extinct Late Triassic turtle relative known from fossils with a plastron but no complete carapace. Its anatomy documents an early stage in the evolution of the turtle shell.
Turtle camouflage: Coloration and patterning that help turtles avoid detection in their habitats. Shell colors and patterns can conceal turtles or break up their outline.
Armadillo armor: A flexible covering of bony plates embedded in an armadillo’s skin. Unlike a turtle shell, it does not incorporate the ribs and vertebrae into a rigid body case.
Plastron: The ventral, or lower, portion of a turtle’s shell. This bony underside completes the shell’s protective enclosure.
Osteoderm: A bony plate formed within the skin of some vertebrates. Unlike many other bony skin plates, the turtle shell’s main bones derive from the skeleton.
Proganochelys: An extinct Late Triassic turtle with a nearly complete shell and several primitive features. Its fossils preserve an early, largely complete version of the shell.
Turtle locomotion: The ways turtles move on land and through water. Shell shape and mass constrain movement and differ with habitat and lifestyle.
Crocodilian osteoderms: Bony plates embedded in the skin of crocodilians. They add armor above the skeleton instead of transforming the trunk skeleton into a shell.

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