The middle cranial fossa

Bastir et al 2011The middle cranial fossa houses the anterior and lateral portions of the temporal lobes. The evolutionary changes of this area in the human genus have been largely investigated by different teams coordinated by Markus Bastir and Antonio Rosas, at the Museum of Natural History, Madrid, Spain. They suggested that inter-specific differences in its morphology (namely a forward displacement of its anterior tip) can be associated with the relative enlargement of the temporal lobes described in modern humans, when compared with apes. They also provided morphological evidence of general differences in the endocranial base between modern humans and Neandertals. In their last article they include also considerations on the sulcal pattern, as visible on the endocranial surface. We have to keep in mind that the endocranial base is influenced by many different factors, and many of them are not associated with actual brain changes. The central position in the cranial base makes the middle cranial fossa sensitive to the development and evolution of the many surrounding structures. The same authors have shown before that the morphology of the middle cranial fossa is significantly correlated in terms of spatial organization with the morphology of the mandibular ramus due to direct physical interaction, being integrated as a modular unit. This integration can be associated with interactions between basicranium, brain and masticatory system during evolution and development. The middle cranial fossa also correlates significantly with the face, constituting a “bridge” for the interaction between the face and the neurocranium. In sum, the morphology of this area can be influenced by traits and processes associated with the face, with the many factors involved in the morphogenesis of the cranial base, as well as with the endocranial soft tissues (brain, meninges, vessels). Despite the neuroanatomical evidence of relatively larger temporal areas in our species, the exact correspondence and match between middle cranial fossa and temporal lobes may be more complex than a simple equivalence between a structure and its negative mould.

Ana Sofia Pedro


2 responses to “The middle cranial fossa

  • Markus Bastir

    I think an interesting field for more research in this direction could be the study of positional variations of the brain and the associated cranial base in a wider field of comparative anatomy. If specific lobes are larger in a given group and if specific associated cranial base areas are relatively expanded in this group then it is likely (for developmental mechanics and also for parsimony) that lobe expansion and cranial base expansion are related to the same cause. However, it is certainly possible that different brains adopt different positions in the cranial base. If that could be demonstrated it would improve our understanding of these complex relationships.

    • sofiappedro

      Your hypothesis seems very interesting. If morphological changes in the temporal lobes and in the middle cranial fossa are correlated among the various species then probably these changes are related and can be extrapolated in extinct species. However such a study would need many species to achieve a statistical result. Would it be feasible when taking into account that posture and locomotion may be important confounding factors, and there is only one living species that walks upright?

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