The surangular normally lies over the centerof mass of the lower jaw, and thus occupies the most mechanically advantageous site for the attachment of the muscles closing the jaw. This is presumably why the mandibular fenestra is located there. The fenestra and the coronoid process provide additional surface area for muscle attachment at this critical site. In lepidosaurs and some other forms, the coronoid may be a separate element, and the mandibular fenestra is unique to the archosaurs . Lengthening the jaw.
Many vertebrates rely heavily on the speed of jaw closure for prey capture.
Strength is less important than speed in capturing small prey. This function takes no standard vertebrate form. See Untitled Document . Here, the surangular is an irregularly-shaped element which caps the lower jaw. In neopterygians , it may develop a coronoid process, as in tetrapods .