Cranial kinesis

Cranial kinesis is movement between bones of the skull during feeding. It is especially developed in birds, snakes, and many fishes.

Quadrate bone: A paired skull bone that articulates with the lower jaw in many vertebrates. Its movement transfers motion between the braincase and jaw in many kinetic skulls.
Vertebrate skull: The bony or cartilaginous structure that supports the brain and sensory organs and forms the jaws. Cranial kinesis describes motion within this broader structure.
Raptorial feeding: Feeding by seizing prey with specialized structures such as jaws, claws, or a beak. Mobile skull elements can help predators seize, hold, or swallow prey.
Akinesis: The absence or near absence of movement between skull bones that are fused or tightly joined. It describes the contrasting condition in which skull bones do not move during feeding.
Jugal arch: A bony arch along the side of the skull, formed by the jugal and adjacent bones. In many birds, its motion helps transmit forces that raise the upper beak.
Skull joint: A connection between skull elements that permits or restricts relative movement. Kinesis depends on joints that allow bones to move relative to one another.
Suction feeding: Prey capture by rapidly expanding the mouth cavity to draw water and prey inward. Some fishes coordinate skull-bone movement with mouth expansion to generate suction.
Streptostyly: A form of skull mobility in which the quadrate bone can rotate relative to the braincase. This specific joint motion is one component of cranial kinesis in many vertebrates.
Pterygoid bone: A paired bone in the palate that connects with other skull bones in many vertebrates. Pterygoid movement links jaw motion to the palate and upper skull.
Jaw articulation: The joint connecting the lower jaw to the skull in vertebrates. Jaw articulation anchors feeding motion and can couple with other skull movements.

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