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theses

Trabecular bone remodels in response to its mechanical loading environment. Thus, different types of loading and locomotion should produce distinctive trabecular architecture, enabling the reconstruction of locomotor regime from trabecular bone. While this relationship has been investigated in the appendicular skeleton of extant and fossil primates, it has yet to be examined in the pelvis, in spite of its central role in hindlimb-driven locomotion. This dissertation explores the relationship between loading, locomotion, and trabecular architecture in the ilium and ischium of a sample of extant primates and attempts to reconstruct locomotion in one fossil specimen, Rudapithecus hungaricus. Based on the general principles of bone functional adaptation, that trabecular architecture remodels via changes in density and anisotropy in response to use, the general predictions of this work are that primates subjecting their innominates to greater, more stereotyped loads will have denser and/or more anisotropic trabecular architecture relative to primates that load their pelves less or in less stereotyped ways. I used high-resolution X-ray computed tomography scans of 29 innominates to compare standard measures of density and anisotropy within and between seven species of primates utilizing different locomotor modes. My results provided mixed support for loading and locomotor hypotheses. In the ilium, intraspecific analyses and interspecific density results sometimes corresponded to predictions, while interspecific comparisons of anisotropy more clearly indicated support for locomotor hypotheses (as has been seen in previous work). Specifically, these comparisons suggested that semi-terrestrial/terrestrial quadrupeds have more anisotropic trabecular architecture than arboreal suspensors. Additionally, for non-human primates, comparisons within phylogenetic groups produced anisotropy results that conformed to locomotor predictions. In the ischium, bending (dorsal compression/ventral tension) appears to be the dominant loading regime in non-human primates, as the dorsal column of trabecular bone tends to be denser and more anisotropic than the ventral column. In terms of the interspecific locomotor hypotheses, differences appear to exist between the trabecular architecture of terrestrial and arboreal primates, as well as between taxa belonging to different locomotor categories, though these differences did not always conform to predictions. Results of the attempt to reconstruct loading in Rudapithecus (proposed to be an arboreal quadruped with adaptations to below-branch suspension) suggested that it had the greatest similarity in trabecular architecture to Symphalangus syndactylus, which is not inconsistent with its predicted locomotor regime.

ETD_7666

Ph.D.

Includes bibliographical references

by Darshana F. Shapiro

doi:10.7282/T32N54MW

ETD doctoral

The author owns the copyright to this work.