The temporalis muscle (or temporal muscle) is one of the mastication muscles; if you clench and unclench your jaw, you can see and feel it contracting at the temples on both sides of your head. It's attached to the mandible (jaw) and to the skull's temporal bone, or temporal fossa. The temporal fascia is a strong, fibrous investment that covers the temporal muscle. Contracting the temporalis muscle lifts the jaw, while the muscle's rear fibres (which are almost horizontal) cause the jaw to retract.