Sclerite

A sclerite (Greek σκληρός, sklēros, meaning "hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly to the hardened parts of arthropod exoskeletons and the internal spicules of invertebrates such as certain sponges and soft corals. The term scleritome, used often in paleontology, refers to the complete set of sclerites of an organism, often all that is known from fossil invertebrates.

Sclerites in combination

Sclerites may occur practically isolated in an organism, such as the sting of a cone shell or they can occur more or less scattered, such as tufts of defensive sharp, mineralised bristles as in many marine Polychaetes or they can occur as structured, but unconnected or loosely connected arrays, such as the mineral "teeth" in the radula of many Mollusca, or the valves of Chitons. When sclerites are organised into such an unarticulated structure, that structure may be referred to as a scleritome, a term largely used in paleontology.