Mandible
Irregular bone of the axial skeleton
Also known as: Jawbone
Classification
Irregular bone of the axial skeleton
Dimensions
Varies widely by species, featuring a horseshoe-shaped horizontal body that curves upward at the back into distinct upright branches.
Key Features
Characterized by a curved, sturdy lower arch that anchors teeth along the top edge, sweeping upward at the rear into a high corner point designed for muscle attachment.
Similar Bones
Can occasionally be confused with fragments of the upper jaw or heavy skull plates, but is easily distinguished by its distinct curved trough housing teeth and the prominent upward-reaching rear corner.
Across Species
In mammals, the jawbone is a single solid piece per side, highly specialized for chewing and holding various types of teeth. Herbivores like horses feature long, flat-topped grinding teeth, while carnivores possess sharp, pointed teeth for shearing. Birds have transformed this area into lightweight, bony beaks entirely lacking teeth.
Evolutionary History
The mammalian jawbone has a fascinating evolutionary journey originating from several smaller bones found in the lower jaws of our ancient reptile-like ancestors. Over millions of years of deep time, these extra bones shrank and migrated to the back of the skull to form the tiny bones of the inner hearing apparatus, leaving just one main structural bone to form the lower jaw.
Photography Tips
Take pictures from the side to capture the overall curve and height of the upright back section, and from a top-down angle to clearly show the row of teeth and the inner surface.