How do osteoglossomorph jaws differ from the protrusible jaws of many other fishes?

Unlike the protrusible jaws found in many other fishes, the jaws of osteoglossomorphs are not protrusible. While many other fish species have evolved the ability to extend their jaws outward to capture prey, osteoglossomorphs possess strongly toothed jaws that remain fixed in their position.1

Despite this lack of protrusion, these fish are highly effective predators. In piscivorous (fish-eating) species, the gape of the mouth can be considerable, allowing them to consume relatively large prey. Furthermore, osteoglossomorphs are unique among fishes for using their tongue as an opposing surface for their teeth when biting into food.12