Exoskeleton

An exoskeleton is a structural covering on an animal’s exterior that supports and protects its body. It can also provide attachment points for muscles and limit water loss.

Arthropod cuticle: The layered external covering of arthropods, made chiefly of chitin and proteins. Its hardened regions form the familiar armor of insects, spiders, and crustaceans.
Arthropoda: The animal phylum that includes insects, arachnids, myriapods, and crustaceans. Most familiar exoskeletons belong to members of this diverse phylum.
Insect flight: The aerodynamic and muscular process by which insects generate lift and maneuver in flight. The thoracic exoskeleton anchors flight muscles and transmits their forces to the wings.
Cambrian explosion: A period of rapid animal diversification and fossil appearance beginning about 539 million years ago. The fossil record shows widespread mineralized animal skeletons emerging during this interval.
Chitin: A tough structural polysaccharide found in arthropod cuticles and fungal cell walls. This polymer gives many exoskeletons tensile strength.
Calcium carbonate: An inorganic compound that forms the principal mineral component of many shells and skeletons. Molluscan shells and crustacean cuticles can gain rigidity from mineral deposits.
Crab: A decapod crustacean with a broad, usually short abdomen and a hard carapace. Its mineralized shell shows how an exoskeleton can protect and support a large-bodied animal.
Trilobite: An extinct marine arthropod with a segmented, mineralized exoskeleton, abundant in Paleozoic fossils. Its preserved armor reveals the form and evolution of early arthropod skeletons.
Sclerotization: A chemical process that hardens and darkens arthropod cuticle through cross-linking of its components. It turns flexible cuticle into rigid plates and protective structures.
Collagen: A family of structural proteins that forms fibrous frameworks in animal tissues. Collagen supports mineralized external structures in some invertebrates.

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