Geometry and evolutionary parallelism in the long bones of cavioid rodents and small artiodactyls.
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Date
2011-12
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Abstract
Morphological parallelism between South American cavioid rodents and small artiodactyls from the Old World has
been postulated for a long time. Our study deals with this question from the point of view of biomechanical
characteristics of the long bones. For this, cross-sectional area, second moment of the area, polar moment, athletic
ability indicators and strength were calculated for the long bones (i.e. humerus, radius, femur and tibia) of five
species of cavioids and two species of artiodactyls. Regressions of all these variables to body mass were established.
Regarding the cross-sectional area, the confidence intervals show that the exponents calculated are not significantly
different from the geometrical predicted value. The exponents obtained for the second moment of area and the polar
moment are not significantly different from the geometrical prediction, except for the humerus. The two indicators of
athletic ability scaled as expected, but the bending indicator of athletic ability of the femur was not correlated to body
mass. The exponent calculated for femur strength is not different from zero, while the strength of the humerus
decreases slightly with the body mass. Additional statistical tests (ANCOVAs) showed no difference between the
values of these variables calculated for the samples studied of artiodactyls and rodents. The present results are
consistent with the hypothesis that there is significant evolutionary parallelism between cavioid rodents and small
artiodactyls.
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Keywords
Adaptation, artiodactyls, cavioids, long bones, mechanics, scaling, skeletal geometry
Citation
Rocha-Barbosa O, Casinos A. Geometry and evolutionary parallelism in the long bones of cavioid rodents and small artiodactyls. Journal of Biosciences. 2011 Dec; 36 (5): 887-895.