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


A New Look at Frontal Bone Ontogeny

CAITLIN L. IBARRA1 and GARY D. RICHARDS2.

1Department of Anthropology, California State University East Bay, 2Biomedical Sciences, University of the Pacific

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In the past, frontal bone ontogeny has been studied as a single unit focusing on ectocranial dimensions. With recent advances in skeletal genetics and molecular biology we, have observed multiple genetic influences affecting frontal development. This has given reason to look at the development of the frontal bone in a new light. We investigate the ontogeny of the frontal bone, looking at its overall development and the differences between ectocranial and endocranial functional units.

Our sample comprises dry skulls divided into four age categories (n=32), 1-1.5, 3-3.5, 5-5.5 and 7-7.5 years-of-age. The sample was scaled on cranial index to eliminate cranial size as a variable. We made a series of metric and nonmetric comparisons from dry skulls and isosurfaces and meshes generated from CT reconstructions.

We found that the ectocranial surface exhibits the greatest amount of developmental difference. The endocranial surface, is alternatively, fairly stable. Although, the endocranium shows little change over the development time examined, we observed overall increases in length with age coupled with decreases in width at the base. The ectocranium increases in length and orbital width although there is a very stable region between the two bosses and the nasal region.

The endocranial and ectocranial aspects of the frontal bone have different developmental trajectories, possibly related to genetic influences on specific regions of the frontal bone. Having identified specific growth regions of the frontal and the morphological changes that result during ontogeny allows clarification of evolutionary and pathologic changes in frontal morphology.

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