the primary upper jaw in gnathostomatous vertebrate animals and man.
In cartilaginous fish and in the larvae of amphibians, the palatoquadrate cartilage functions as a jaw; in bony fish, terrestrial vertebrates, and man, it becomes part of the palate with the development of secondary jaws. Articulation of the palatoquadrate cartilage with the skull may be amphistylic, hyostylic, or autostylic. In all bony fish, terrestrial vertebrates, and man, the palatine, pterygoid, and quadrate bones are formed at the site of the palatoquadrate cartilage. (The quadrate bone serves to articulate the lower jaw with the skull and in mammals, including man, becomes one of the auditory ossicles—the incus.)