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  ScienceZoologyReptiles and AmphibiansOrder Chelonia
A Turtle's Shell

A turtle's shell consists of two layers. The inner layer is made up of bony plates and is actually part of the skeleton. Among most species, the outer layer consists of hard, horny structures called scutes, which are formed from skin tissue. Soft-shelled turtles and the leatherback turtle have an outer layer of tough skin rather than scutes. The part of the shell that covers the turtle's back is called the carapace, and the part that covers the belly is called the plastron. The carapace and the plastron are joined along each side of the body by a bony structure called the bridge.

Most turtles that live on land have a high, domed shell. Those that live in water have a flatter, more streamlined shell. Many species of turtles can pull their head, legs, and tail into their shell for protection. A few kinds of turtles, particularly sea turtles, cannot withdraw into their shell. Some species of turtles, including Blanding's turtle, box turtles, and mud turtles, have a hinged plastron. These turtles can close the plastron tightly against the carapace after withdrawing into their shells.

The World Book Encyclopedia. Chicago: World Book-Childcraft International, 1979

The Skeleton of a Land Turtle

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This page was last updated on January 19, 2015.

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