Bichir
Bichirs (Polypterus) belong to a very ancient group of fishes, the crossopterygians, and have kept many of the characteristics of their ancestors including their jaws. Primitively, the bones that make up the jaws in modern teleosts were fused to the skull. This primitive condition might look a little prehistoric, but it still works for Polypterus.
Predators
Predators have long jaws optimized for speed in which sharp, conical teeth spear the prey to prevent its escape. In the barracuda (Sphyraena spp.) teeth toward the back of the oral jaw butcher large fishes into swallowable pieces. Tigerfishes (Hydrocyon spp.) are muscular predators that chase down their prey before delivering a killing bite, just like their terrestrial namesakes. The slingjaw wrasse (Epibulus insidiator) is just as effective a predator, but it adopts a more lazy approach by telescoping its oral jaws to the prey, rather than moving its entire body.
Filter Feeders
Filter feeders have lost their oral teeth and rely on modified gill rakers to strain tiny animals and plants from sediments (Cyprinus spp.) or the water column (Clupea spp.).
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