Figure 1. Craniofacial skeleton of an adult zebrafish. An x-ray of an adult zebrafish reveals segmented pharyngeal arch skeletal elements that closely resemble those of higher vertebrates. Abbreviations: m, mandible; mx, maxilla; n, nasal; ot, otoliths; pa1-5, pharyngeal arches 1-5; pt, pharyngeal teeth; q, quadrate; and sy, symplectic.