A hard, plate-like structure that covers or protects the gills of certain crustaceans, sometimes fused with the jaw region.
From Greek gnathos (jaw) plus stegites (roofed or covered), referring to the protective covering near the jaw area in some crustaceans.
Crustaceans evolved these protective plates that basically act like a roof over their gills—and they're located right near the jaw, so early scientists thought they were related to jaw structures!
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