Geometry and evolutionary parallelism in the long bones of cavioid rodents and small artiodactyls |
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Authors: | O Rocha-Barbosa A Casinos |
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Institution: | 1.Laboratório de Zoologia de Vertebrados (Tetrapoda) (LAZOVERTE), DZ, IBRAG,Universidade do Estado do Rio de Janeiro,–Rio de Janeiro,Brazil;2.Departament de Biologia Animal (Vertebrats),Universitat de Barcelona,Barcelona,Spain |
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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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