The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Cross-sectional geometry of the mandible in neonatal common marmosets (Callithrix jacchus)


1Department of Anatomy and Neurobiology, Skeletal Biology Research Focus Area, Northeast Ohio Medical University (NEOMED), 2School of Biomedical Sciences, Cellular and Molecular Biology, Kent State University

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Marmosets are unique among callitrichids in habitually gouging trees with their anterior teeth to stimulate exudate flow. Previous data suggest that adult marmosets do not generate relatively large bite forces during gouging and their mandibles display decreased load-resistance ability relative to closely-related non-gouging tamarins. We test the hypothesis that the differences in cross-sectional morphologies between adult marmosets and tamarins are present in the jaws of neonatal marmosets compared to tamarins.

Jaws from six stillborn common marmosets (Callithrix jacchus) and cotton-top tamarins (Saguinus oedipus), respectively, were microCT scanned at 20.5┬Ám resolution. We quantified the cross-sectional properties and mechanical indices of cortical bone using slices perpendicular to the occlusal plane at the symphysis and midpoint of each deciduous tooth.

Results suggest little difference in absolute cross-sectional area between marmoset and tamarin neonates. Adjusting for jaw length as a biomechanical standard, marmoset neonates appear relatively robust, particularly in the premolar region. Parasagittal bending resistance follows adult trends with neonatal marmosets displaying decreased load-resistance ability compared to tamarins, except in anterior premolar region. Relative bending-resistance ability (Ixx/jaw length) is greater in neonatal marmosets compared to tamarins, contrasting with the adult pattern. The relative robusticity of neonatal marmosets is likely due to their absolutely shorter jaws at birth. Ontogenetic data indicate that the initially short marmoset jaw undergoes accelerated postnatal growth and is relatively elongated at weaning. These data suggest the postnatal changes in the marmoset mandible, resulting in reduced load-resisting ability compared to tamarins, may result from plasticity related to dietary processing.

This work was funded by grants from the National Science Foundation (BCS-0959438; BCS-0412153).

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