The temporalis does not have the quadrilateral shape of the masseter but rather is shaped like a fan. The origin is very long, starting at the sphenoid bone and extending along the frontal, parietal and temporal bones between the superior and inferior temporal lines. The most anterior fibers descend vertically deep to the zygomatic arch to attach along the entire anterior portion of the coronoid process. The majority of the fibers travel anteriorly as they descend and join a large tendon that passes deep to the zygomatic arch to insert on the coronoid process. The large number of fibers makes this a powerful muscle even though it is not as thick as the masseter. This muscle is involved in forcibly elevating the mandible and the posteriorly placed fibers act to retract the mandible. The temporalis is unique in the muscle of mastication in that it is the only one that is the prime mover for retraction. Like the masseter this muscle is superficial and can be felt tensing when clenching or moving the mandible posteriorly.