Jaw abnormality sagittally divides the face into five equal parts: It is insufficient to derive at a diagnosis of jaw deformity solely based on the clinical examination. Hence, additional information is gathered from diagnostic tests, which may include dental model analyses and radiographic imaging studies. Mandibular micrognathia is the condition when lower jaw is smaller than normal. Failure of the ramus to develop will give rise to micrognathia.<ref name="Elsevier/Churchill Livingstone"></ref> Micrognathia can be classified as either congenital or acquired. Clinical appearance of some patients with congenital type of mandibular micrognathia can have a severe retrusion of the chin but by actual measurements,
Jaw of the mammalian jaw, two of the bones of the jaw structure (the articular bone of the lower jaw, and quadrate) were reduced in size and incorporated into the ear, while many others have been fused together. As a result, mammals show little or no cranial kinesis, and the mandible is attached to the temporal bone by the temporomandibular joints. Temporomandibular joint dysfunction is a common disorder of these joints, characterized by pain, clicking and limitation of mandibular movement. Sea urchins possess unique jaws which display five-part symmetry, termed the "Aristotle's lantern". Each unit of the jaw holds a single,