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The group is traditionally a superclass, including the familiar classes of fish, birds, and so forth, and a sister group of the jawless vertebrates Agnatha. However, recent genetic studies are causing a reassessment of Gnathostomata as a grouping.

Other distinguishing characteristics of living gnathostomates are the myelin sheathes of neurons, and an adaptive immune systemThe immune system is any system present in an organism to prevent predation by biological agents. All living organisms have these protective measures, although they vary radically in scope and mechanism. In humans and domesticated animals, the immune syst.

The traditional classes of Gnathostomata include:

• Placodermi - extinct
• Chondrichthyes (cartilagenous fish)
• Acanthodii - extinct
• Osteichthyes (bony fish)
  • subclass SarcopterygiiCoelacanthimorpha Coelacanths Dipnoi Lungfishes Tetrapoda Sarcopterygii is traditionally the class of lobe-finned fishes, consisting of lungfish and coelacanths. Most taxonomists who subscribe to the cladistic approach include within this group the subcla (lobe-finned fish)
  • subclass ActinopterygiiSee text The Actinopterygii are the ray-finned fish . They are the dominant group of vertebrates, with over 27,000 species ubiquitous throughout fresh water and marine environments. They are traditionally treated as a subclass of the Osteichthyes, or bony (ray-finned fish)
• AmphibiaSubclass Labyrinthodontia extinct Subclass Lepospondyli extinct Subclass Lissamphibia Urodela Anura Gymnophiona The class Amphibia consists of all tetrapods (four-legged vertebrates) that do not have amniotic eggs. Amphibians generally spend part of their ( amphibians)
• Reptilia (reptiles)
• Aves (birds)
• Mammalia (mammals)

External link

• Tree of Life discussion of Gnathostomata