How do the jaws of atheriniform fishes protrude while feeding?

In atheriniform fishes, the protrusion of the jaws is achieved through a mechanism distinct from that of typical acanthopterygians. Rather than utilizing a complex system of joints and ligaments, atheriniforms protrude their jaws by twisting the maxilla and displacing its head forward.

The structural basis for this movement involves a simple, shelflike head of the maxillary bone, which is attached to the palate solely by ligaments rather than a mobile joint. Additionally, the premaxilla—the bone forming the front of the upper jaw—is longer than the maxilla and possesses a simple head, facilitating this specialized movement during feeding.1