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An exoskeleton (from Greek Î­Î¾Ï, Ã©xÅ outer and ÏÎºÎµÎ»ÎµÏÏÏ, skeletos skeleton) is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton (endoskeleton) of, for example, a human. In usage, some of the larger kinds of exoskeletons are known as shells.
One advantage an exoskeleton provides is a strong outer layer that acts as armor against predators and environmental hazards. It also serves as a protective water barrier, and it imparts advantages related to structure and mobility. Like endoskeletons, exoskeletons provide structure and support to an animal's body. However, exoskeletons encase all of an animal's living tissues, protecting them from damage and attack. Muscles used for locomotion attach directly to the exoskeleton, giving the animal better leverage for rapid movement. One of the most important functions of an exoskeleton is to prevent land-dwelling species from drying out.