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In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: symphysis menti) or line of junction where the two lateral halves of the mandible typically fuse in the first year of life (6–9 months after birth). [1]
The unfused mandibular symphysis and constricted roots of the lower postcanines support the placement of Alemoatherium within Prozostrodontia, a clade of cynodonts including mammaliaforms and many of their Late Triassic relatives, from Prozostrodon crownwards.
Strepsirrhines are also traditionally noted for their unfused mandibular symphysis (two halves of the lower jaw), [87] however, fusion of the mandibular symphysis was common in adapiforms, [92] notably Notharctus. [93] Also, several extinct giant lemurs exhibited a fused mandibular symphysis. [94]
The postorbital bar (or postorbital bone) is a bony arched structure that connects the frontal bone of the skull to the zygomatic arch, which runs laterally around the eye socket. It is a trait that only occurs in mammalian taxa, such as most strepsirrhine primates [1] and the hyrax, [2] while haplorhine primates have evolved fully enclosed ...
The mandible has two main holes , found on both its left and right sides: The mandibular foramen, is above the mandibular angle in the middle of each ramus. The mental foramen sits on either side of the mental protuberance (chin) on the body of mandible, usually inferior to the apices of the mandibular first and second premolars. As mandibular ...
The mandibular symphysis divides below and encloses a triangular eminence, the mental protuberance, the base of which is depressed in the center but raised on either side to form the mental tubercle. The two mental tubercles along with the medial mental protuberance are collectively called the mental trigone.
The symphysis of the external surface of the mandible divides below and encloses a triangular eminence, the mental protuberance, the base of which is depressed in the center but raised on either side to form the mental tubercle. The size and shape of the bones making up this structure are responsible for the size and shape of a person's chin.
Sometimes (e.g. in bony fish), the maxilla is called "upper maxilla", with the mandible being the "lower maxilla". Conversely, in birds the upper jaw is often called "upper mandible". In most vertebrates, the foremost part of the upper jaw, to which the incisors are attached in mammals consists of a separate pair of bones, the premaxillae ...