masseter muscle morphology trait masseter muscle size trait Trait.ontology Any measurable or observable characteristic related to the physical magnitude of the masticatory muscle of the posterior cheek with origin from the inferior border and medial surface of the zygomatic arch, with insertion into the lateral surface of the ramus of the mandible, with nerve supply from the masseteric nerve, and whose action closes the jaw during chewing. VT:0004236 masticatory muscle size trait