Bones come in several different types. Long bones are longer than they are wide. The length of the bone, or shaft, widens at the extremities (ends). Short bones are cubelike, about as long as they are wide. Flat bones, such as ribs or skull bones, are thin or flattened. Irregular bones, such as vertebrae, facial bones, or hip bones, have specific shapes, unlike the other types of bones. The following two bone types are usually classified separately: Sesamoid or round bones, such as the kneecap, are found embedded within certain tendons. Sutural or Wormian bones occur between the sutures (joints) of the cranial bones of the skull.