Protuberance or fossa on the lateral surface of the mandible in primates.

Some primates have a protuberance on the lateral surface of the mandible, and some have a fossa. We investigated some species of primates in order to clarify morphological characteristics of the protuberance and/or fossa on the lateral surface of the mandible by using computed tomography. Both protuberance and fossa were found in some species of the Macaca, and each structure was found about 10%. The protuberance was found in the Cercocebs and Cercopithecus, and the fossa was found in the Papio, Mandrillus, Colobus and Hylobates. The protuberance didn't appear until M3s erupted. Well-developed protuberance was laid from P4 to M3 region. There found 3 types of protuberances; (1) the protuberance continue on the oblique line, (2) the protuberance is localized on the mandibular base, (3) the protuberance is situated the central part of the mandibular body. The 3rd type was often well-developed. The protuberance was composed of compact bone, and was similar to the mandibular tori in humans that were found on the internal surface of the mandible. There were the 3 types of the fossa; (1) the bone width of the mandible was thin in the center of the fossa, (2) the curvature of the external table of the mandible made a fossa, (3) the external surface of the mandible was looked like concave because of the thickened mandibular base. In the 2nd and 3rd types, the mandibular thickness did not change between the area of fossa and the other area. The 1st type of fossa was found in the Papio and Mandrillus, the 2nd type was found in the Macaca, Cercocebs and Cercopithecus, and the 3rd type was found in the Hylobates and Colobus. [ABSTRACT FROM AUTHOR]