Postglenoid Process Development

This feature is associated with the requirements of the masticatory apparatus. While it might be thought that this feature should be integrated with glenoid fossa depth, this is not the case, for the depth of the fossa and the development of the process are clearly not coupled. For example, both Gorilla and Pan have a similar development of the postglenoid process (large and anteriorly set), yet while Gorilla has intermediate depth of the glenoid fossa, it is shallow in Pan. Differential patterns between these two character states may suggest distinct excursive movements of the mandible or differential adaptive responses in TMJ morphology (dependent on two different ancestral conditions) to help stabilize the joint that is a functional convergence as opposed to a morphological convergence.

Four conditions are recognized here: a large process that is anteriorly set and not fused to the tympanic (= 0), as seen in Pongo, Gorilla, Pan, and Praeanthropus (Strait et al., 1997); a medium-sized process that may or may not be fused to the tympanic (= 1), as observed in Dryopithecus, Australopithecus, P. walkeri, and K. rudolfensis (Kordos & Begun, 1997; Strait et al., 1997; Begun, 2002); a small process that may be fused or unfused (= 2), as observed in P. boisei (Strait & Grine, 2001); and a small process that is fused to the tympanic (= 3), as observed in P. robustus, H. habilis, and H. sapiens. A small and fused process defines all East

African specimens of H. habilis (Strait et al., 1997). While Sahelanthropus is described as having a large postglenoid process, no information is provided regarding whether it is fused to the tympanic (Brunet et al., 2002). It is allocated here as displaying the primitive hominid condition.

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  • daniela
    What is the postglenoid process?
    8 years ago

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