An
exoskeleton (from Greek έξω,
éxō "outer" and σκελετός,
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". Examples of exoskeleton animals include
insects such as
grasshoppers and
cockroaches, and
crustaceans such as
crabs and
lobsters. The
shells of certain
sponges and the various groups of shelled mollusks, including those of
snails,
clams,
tusk shells,
chitons and
nautilus, are also exoskeletons.