Jaw

The jaws are a pair of opposable articulated structures at the entrance of the mouth, typically used for grasping and manipulating food.

The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of humans and most animals.

The vertebrate jaw is derived from the most anterior two pharyngeal arches supporting the gills, and usually bears numerous teeth.

The vertebrate jaw probably originally evolved in the Silurian period and appeared in the Placoderm fish which further diversified in the Devonian.

[5] Sea urchins possess unique jaws which display five-part symmetry, termed the Aristotle's lantern.

Each unit of the jaw holds a single, perpetually growing tooth composed of crystalline calcium carbonate.

Human lower jaw viewed from the left
The mandibles of a bull ant
Jaws of a great white shark
Moray eels have two sets of jaws: the oral jaws that capture prey and the pharyngeal jaws that advance into the mouth and move prey from the oral jaws to the esophagus for swallowing.