Parietal depressions in skulls of the extinct saber-toothed felidSmilodon fatalis: evidence of mechanical strain

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Abstract
Examination of nearly one thousand skulls and braincases of the Pleistocene North American felid Smilodon fatalis revealed localized depressions in the parietal bones in 36% of the sample. The depressions are hypothesized to be the consequence of heightened local mechanical stresses in fibers of the temporalis muscle. Comparative dissections of modern felids indicate that this region is the attachment site for deep temporalis bundle fibers where masticatory stresses in this muscle would naturally be manifested. The depressions occur in skulls of a variety of extant and extinct carnivorans. Inferences from computerized axial tomographic scans and clinical observations of bone pathology indicate that the depressions are most likely cortical desmoids, bony defects created by avulsive processes associated with overexertion in highly active muscles.