Scaling and mechanics of the felid calcaneus: Geometric similarity without differential allometric scaling

TY - JOUR

T1 - Scaling and mechanics of the felid calcaneus

T2 - Geometric similarity without differential allometric scaling

AU - Gálvez-López, Eloy

AU - Casinos, Adrià

PY - 2012/6/1

Y1 - 2012/6/1

N2 - Six mechanically significant skeletal variables were measured on the calcanei from 60 Felidae specimens (22 species) to determine whether these variables were scaled to body mass, and to assess whether differential scaling exists. The power equation (y=a·x b) was used to analyse the scaling of the six variables to body mass; we compared traditional regression methods (standardised major axis) to phylogenetically independent contrasts. In agreement with previous studies that compared these methodologies, we found no significant differences between methods in the allometric coefficients (b) obtained. Overall, the scaling pattern of the felid calcaneus conformed to the predictions of the geometric similarity hypothesis, but not entirely to those of the elastic similarity hypothesis. We found that the moment arm of the ankle extensors scaled to body mass with an exponent not significantly different from 0.40. This indicated that the tuber calcanei scaled to body mass faster than calcaneus total length. This explained why the effective mechanical advantage of the ankle extensors increased with body mass, despite the fact that limb posture does not change in felid species. Furthermore, this finding was consistent with the hypothesis of the isometric scaling of ground reaction forces. No evidence for differential scaling was found in any of the variables studied. We propose that this reflected the similar locomotor pattern of all felid species. Thus, our results suggested that the differences in allometric coefficients for 'large' and 'small' mammals were in fact caused by different types of locomotion among the species included in each category.

AB - Six mechanically significant skeletal variables were measured on the calcanei from 60 Felidae specimens (22 species) to determine whether these variables were scaled to body mass, and to assess whether differential scaling exists. The power equation (y=a·x b) was used to analyse the scaling of the six variables to body mass; we compared traditional regression methods (standardised major axis) to phylogenetically independent contrasts. In agreement with previous studies that compared these methodologies, we found no significant differences between methods in the allometric coefficients (b) obtained. Overall, the scaling pattern of the felid calcaneus conformed to the predictions of the geometric similarity hypothesis, but not entirely to those of the elastic similarity hypothesis. We found that the moment arm of the ankle extensors scaled to body mass with an exponent not significantly different from 0.40. This indicated that the tuber calcanei scaled to body mass faster than calcaneus total length. This explained why the effective mechanical advantage of the ankle extensors increased with body mass, despite the fact that limb posture does not change in felid species. Furthermore, this finding was consistent with the hypothesis of the isometric scaling of ground reaction forces. No evidence for differential scaling was found in any of the variables studied. We propose that this reflected the similar locomotor pattern of all felid species. Thus, our results suggested that the differences in allometric coefficients for 'large' and 'small' mammals were in fact caused by different types of locomotion among the species included in each category.

KW - Biomechanics

KW - Calcaneus

KW - Differential scaling

KW - Effective mechanical advantage

KW - Felidae

KW - Phylogenetically independent contrasts

KW - Scaling

UR - http://www.scopus.com/inward/record.url?scp=84860441597&partnerID=8YFLogxK

U2 - 10.1111/j.1469-7580.2012.01502.x

DO - 10.1111/j.1469-7580.2012.01502.x

M3 - Article

C2 - 22463377

AN - SCOPUS:84860441597

SN - 1469-7580

VL - 220

SP - 555

EP - 563

JO - Journal of Anatomy

JF - Journal of Anatomy

IS - 6

ER -