The hyomandibula is the large, dorsal-most member of the hyoid arch. It begins ossifying in the dorsal edge of the hyosymplectic cartilage near the hyomandibular foramen (4.6 mm NL). Ossification spreads through the cartilage, and sheets of membrane bone form off the cartilage model anteriorly and posteriorly (6.6 mm). In the adult, the hyomandibula has cartilage-capped anterior and posterior articulating heads that meet the sphenotic-prootic fossa and the pterotic fossa, respectively, in synovial joints. A posterior knob of bone develops, also capped in cartilage, and it forms a synovial joint with the opercle. [ GOC:mh ORCiD:0000-0001-9114-8737 ]