Gnathostomata (pronounced /ˌneɪθɵstoʊˈmɑːtə/) is the group of vertebrates with jaws. The term derives from Greek γνάθος (gnathos) "jaw" + στόμα (stoma) "mouth".
The group is traditionally a superclass, broken into three top-level groupings: Chondrichthyes, or the cartilaginous fish; Placodermi, an extinct clade of armored fish; and Teleostomi, which includes the familiar classes of bony fish, birds, mammals, reptiles, and amphibians. Some classif...
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Gnathostomata (pronounced /ˌneɪθɵstoʊˈmɑːtə/) is the group of vertebrates with jaws. The term derives from Greek γνάθος (gnathos) "jaw" + στόμα (stoma) "mouth".
The group is traditionally a superclass, broken into three top-level groupings: Chondrichthyes, or the cartilaginous fish; Placodermi, an extinct clade of armored fish; and Teleostomi, which includes the familiar classes of bony fish, birds, mammals, reptiles, and amphibians. Some classification systems have used the term Amphirhina. It is a sister group of the jawless craniates Agnatha.
Recent genetic studies are causing a reassessment of Gnathostomata as a grouping.
New fossil finds suggests thelodonts as the closest relatives of the Gnathostomata.
It is believed that the jaws evolved from anterior gill support arches that had acquired a new role, being modified to pump water over the gills by opening and closing the mouth more effectively — the buccal pump mechanism. The mouth could then grow bigger and wider, making it...
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