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 system.
The traditional classes of Gnathostomata include:
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