The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

The Lateral Angle and cranial base sexual dimmorphism: a morphometric evaluation


Laboratory of Biological Anthropology, University of Copenhagen

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The lateral angle (LA) is formed by the internal meatus acousticus (IMA) and the medial surface of the petrous bone, and the LA size has been proposed as a method for sex evaluation. The aim of this study was to determine the association between petrous bone morphology, and hence the LA size, and that of the cranial base.

CT scans of the heads of 51 female and 51 male autopsy cases were used. The LA was measured by direct measurement on CT-scan slices, and 12 landmarks were identified using 3D visualizations of the internal cranial base. Procrustes superimposition was used to extract the shape information from the set of coordinates.

We found a significant sexual dimorphic difference in cranial base shape, but with a large overlap and low predictive rate (76.6%) with high misclassification values. The male cranial base shape was more elongated, but also narrower in the IMA region with a shorter distance between the IMA and the labyrinth, than females. While this difference is in agreement with the LA size being smaller for males than for females, we also found a large overlap in LA sizes. Thus, we posit that LA size is a reflection of the petrous bone and cranial base shape and that given the rather low degree of sexual dimorphism in this area, it follows that the LA will have a low degree of sexual dimorphism.

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