The mandible, or lower jaw bone, is a type of irregular bone. Irregular bones are those that, because of their different shape, do not fit into another category of bones. Other good examples of irregular bones are the vertebrae.
Four other types of bones exist. They are the long bones, short bones, flat bones and sesamoid bones. The humerus in the arm and the femur in the leg are examples of long bones. The carpals in the wrist and the tarsals in the ankle are short bones. The ribs and scapula are examples of flat bones, and the patella, or kneecap, is a sesamoid bone.