The Supraorbital Torus: "A Most Remarkable Peculiarity" [and Comments and Replies]

@article{Russell1985TheST,
  title={The Supraorbital Torus: "A Most Remarkable Peculiarity" [and Comments and Replies]},
  author={M D Russell and Tasman Brown and StanleyM. Garn and Fakhry Giris and Spencer Turkel and Mehmet Yaşar Işcan and Ordean J. Oyen and Burkhard Jacobshagen and Michael Pietrusewsky and G Philip Rightmire and Fred H. Smith and Christy G. Ii Turner and Srboljub Živanovi{\'c}},
  journal={Current Anthropology},
  year={1985},
  volume={26},
  pages={337 - 360}
}
The supraorbital torus is found only in some genera of the primate order. Because no muscles of consequence attach directly to it, it has been considered nonfunctional. However, invitro strain-gauge experiments demonstrate that when the anterior teeth are loaded, the supraorbital region acts as a bent beam, pulled downward on each end by masticatory muscle forces and pushed upward centrally by bite force. Clinical and experimental data indicate that in response to repeated dynamic bending… 

Masticatory-stress hypotheses and the supraorbital region of primates.

There is no good reason to believe that enlarged browridges in living and/or fossil primates are structural adaptations to counter intense masticatory forces.

THE SUPRAORBITAL REGION OF PRIMATES

It was found that the supraorbital region of Macaca fascicularis and Papio anubis is strained relatively little during mastication and incision, which indicates that in macaques and baboons there is much more supraorbitals bone than is needed to counter masticatory loads, which suggests that their brow-ridges could be considerably smaller yet still counter masticallyatory stress without structural failure.

Endo's stress analysis of the primate skull and the functional significance of the supraorbital region.

A review of Endo's experimental and theoretical procedures and data indicates that the magnitude of the principal strains in the glabella region of both humans and gorillas are low as compared to other parts of the face and that the supraorbital region in extant humans cannot be accurately modeled as a beam.

Masticatory loading and bone adaptation in the supraorbital torus of developing macaques.

This work develops three micro-CT-based FEA models of M. fascicularis skulls ranging in dental age from deciduous to permanent dentitions and validated them against published experimental data to evaluate the hypothesis that strain energy density (SED) magnitudes are high in subadult individuals with resulting bone growth in the supraorbital torus.

Interspecific perspective on mechanical and nonmechanical models of primate circumorbital morphology.

  • M. Ravosa
  • Biology
    American journal of physical anthropology
  • 1991
It is suggested that since circumorbital structures (especially the browridges) are located the farthest away from the chewing apparatus, they are least affected by masticatory stresses.

Masticatory stress, orbital orientation and the evolution of the primate postorbital bar.

The visual predation hypothesis of primate origins is reformulate by incorporating in vivo and fossil data and thus offers new insights into major adaptive transformations in the primate skull.

Morphological relationship between the cranial and supraorbital regions in Homo sapiens.

In the sample of all crania, the neurocranial size more strongly influenced the morphological variation of the ST than of the GL, and sex influenced both of these structures the most, suggesting that sex may be the main factor (having an influence independent of the other traits) on the morphologists of theGL and ST.

Strain in the Galago facial skull

Although the strain‐direction data for the galago circumorbital region offer support for the occurrence of facial torsion, the low magnitude of these strains suggests that this loading pattern may not be an important determinant of circumorbitals morphology.
...

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