Chitons (Polyplacophora)

This group gathers Mollusks subcategory members belonging to the class Polyplacophora, the chitons, mollusks immediately recognizable by a flattened, oval body armored across the back with eight overlapping calcareous plates that give the group its scientific name, meaning many-plated. Found clinging tightly to rocks in the intertidal zone and shallow subtidal waters worldwide, a chiton grips its substrate with a broad muscular foot strong enough to resist being pried loose by hand or dislodged by crashing waves, and grazes slowly across rock surfaces using a rasping, tooth-covered feeding structure called a radula to scrape away algae. If dislodged, a chiton can curl its jointed, plated shell into a tight ball much like a pillbug or armadillo, an unusual defensive flexibility made possible by the eight separate plates rather than the single rigid shell most other shelled mollusks carry.