hyoid muscle jaw depressor muscle protractor hyoideus depressor gnathalis geniothoracis AAO:0010655 branchiomandibularis geniohyoideus Muscle that pulls the hyoid apparatus forward and depresses the lower jaw.[AAO] A muscle whose action is to depress the lower jaw. geniohyoideus muscle UBERON:0011151 XAO:0004127 Source: Winterbottom, R. 1973. A Descriptive Synonymy of the Striated Muscles of the Teleostei. Proceedings of the Academy of Natural Sciences of Philadelphia, Vol. 125 (1973), pp. 225-317.[TAO] In amphibians, 'Muscle that pulls the hyoid apparatus forward and depresses the lower jaw.' [AAO:0010655]. 'The protractor hyoideus muscle in teleosts is commonly, albeit mistakenly, referred to as the geniohyoideus muscle, which is involved in the coracomandibularis coupling. According to Edgeworth (1935) and Winterbottom (1974), the protractor hyoideus is composed of a fusion of the intermandibularis posterior and the interhyoideus muscles which resulted in the protractor hyoideus which spans the hyoid and mandible. The intermandibularis spans the mandible while the closely apposed interhyoideus spans the hyoid in other fishes. Furthermore, they concluded that any muscle that is homologous to the geniohyoideus (coracomandibularis coupling) in other lower vertebrates has been lost in teleosts, as well as gars. However, the protractor hyoideus muscle is functionally analogous to the coracomandibularis coupling of other vertebrates and so we use it in our discussion to show the phylogenetically broad roles of these couplings in jaw mechanics.' coracomandibularis relationship loss: subclass hyobranchial muscles (AAO:0000224)[AAO] Muscle located on ventral side of the head, linking the ventral hyoid arch to the dentary. Innervated by ramus mandibularis V and ramus hyoides VII.[TAO] TAO:0000612 protractor hyoidei