We will begin and, until later revision, also end with a brief discussion of gill arches.
Elements derived from the hyoid arch are most conspicuously present in jaw support.
Opinions vary on the mandibular arch, and it may still be that the jaw has some completely different ancestral homologue. However, the gill arch theory is not only elegant, but has the virtue of being easy to learn and remember, which may be why it has dominated the discussion for the last century or so. The segments of a typical gnathostome gill arch are shown in Figure 1. By convention, the corresponding parts of the hyoid arch are named by using the suffix -hyal , as in ceratohyal or basihyal, with the exception of the epihyal , which is more commonly called the hyomandibular , columella or stapes , depending on the subject matter and taxon under consideration and how badly the writer wishes to confuse you. Only the ceratal and epal elements of the mandibular arch are known.