Sclerite

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.

Or, they can occur as structured, but unconnected or loosely connected arrays, such as the mineral "teeth" in the radula of many Mollusca, the valves of chitons, the beak of a cephalopod, or the articulated exoskeletons of Arthropoda.

In Arthropoda, the hardening that produces sclerites is accomplished either by the cross-linking of protein chains in the exocuticle, a process called sclerotization, or by incorporation of minerals such as calcium carbonate into regions of the exoskeleton, or both.

Clamps, the main attachment structure of the parasitic polyopisthocotylean monogenean flatworms,[2][3] are composed of various sclerites and associated musculature, located on a posterior organ called the haptor.

[6] At least one modern gastropod mollusc living near deep sea hydrothermal vents has structures made of iron sulfides similar to some Cambrian sclerites.