Retro-glenoid and homologous angle of superior cervical column in extant primates

The posterior part of the atlas superior articular processes (foveae articu lares superiores atlantis) or the retro-glenoid tubercles, as well as those of the atlas inferior facet (foveae articulares inferiores atlantis) and o f the axis superior facet (facies articularis superior axis), have permitte d the retro-glenoid and homologous angle to be defined. These angles have a major systematic importance in individualizing four extant primates groups : Strepsirhini, Platyrrhini and Cercopithecoidea, non-humans Hominoidea, an d man. This angle permits a better functional and static definition of the superior cervical column, the head being in balanced or unbalanced unstable position. ((C) 1999 Academie des sciences / Editions scientifiques et medi cales Elsevier SAS.).