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The functional significance of the squamosal suture in Australopithecus boisei
Author(s) -
Rak Yoel
Publication year - 1978
Publication title -
american journal of physical anthropology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.146
H-Index - 119
eISSN - 1096-8644
pISSN - 0002-9483
DOI - 10.1002/ajpa.1330490111
Subject(s) - australopithecus , zygomatic arch , anatomy , masticatory force , masseter muscle , mastication , fibrous joint , biology , geology , orthodontics , paleontology , medicine
A juvenile Australopithecus boisei specimen from the Omo basin, southern Ethiopia, is found to exhibit an extraordinarily large overlap of the temporal squama on the parietal, a phenomenon shared with at least two adult specimens of A. boisei. An attempt is made to interpret the overlap as a structural (bony/ligamentous) adaptation necessitated by the unique combination of certain components of the masticatory system of A. boisei . These are: (1) the massiveness and strength of the temporalis muscle, (2) its relatively anterior location, and (3) the lateral position of the masseter muscle due to the flaring of the zygomatic arches. The effect of the temporalis muscle is to create excessive pressure on the portion of the squamosal suture along the parietal, while the lateral placement of the masseter and the resultant increase of pressure on the temporal squama via the zygomatic arch tend to “loosen” the contact between the temporal and parietal bones.