Cyclostomi

Superclass of jawless fishes

Cyclostomi, often referred to as Cyclostomata (from Ancient Greek κύκλος (kúklos), meaning "circle", and στόμα (stóma), meaning "mouth", and thus, "circular mouth") is a superclass of vertebrates that comprises the living jawless fish classes: the lampreys and hagfishes. Both groups have jawless mouths with horny epidermal structures that function as teeth called ceratodontes, and branchial arches that are internally positioned instead of external as in the related jawed fishes.

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