that evolved independently at least five times.

The premaxilla is unattached to the neurocranium (braincase); it plays a role in protruding the mouth and creating a circular opening. This lowers the pressure inside the mouth, sucking the prey inside. The lower jaw and maxilla (main upper fixed bone of the jaw) are then pulled back to close the mouth, and the fish is able to grasp the prey. By contrast, mere closure