Experimental alteration of limb posture in the chicken (Gallus gallus) and its bearing on the use of birds as analogs for dinosaur locomotion
Version of Record online: 2 JUN 1999
Copyright © 1999 Wiley-Liss, Inc.
Journal of Morphology
Volume 240, Issue 3, pages 237–249, June 1999
How to Cite
Carrano, M. T. and Biewener, A. A. (1999), Experimental alteration of limb posture in the chicken (Gallus gallus) and its bearing on the use of birds as analogs for dinosaur locomotion. J. Morphol., 240: 237–249. doi: 10.1002/(SICI)1097-4687(199906)240:3<237::AID-JMOR3>3.0.CO;2-N
- Issue online: 2 JUN 1999
- Version of Record online: 2 JUN 1999
- National Science Foundation. Grant Number: IBN-970963
- bone strain;
Extant birds represent the only diverse living bipeds, and can be informative for investigations into the life-history parameters of their extinct dinosaurian relatives. However, morphological changes that occurred during early avian evolution, including the unique adoption of a nearly horizontal femoral orientation associated with a shift in center of mass (CM), suggest that caution is warranted in the use of birds as analogs for nonavian dinosaur locomotion. In this study, we fitted a group of white leghorn chickens (Gallus gallus) with a weight suspended posterior to the hip in order to examine the effects on loading and morphology. This caused a CM shift that necessitated a change in femoral posture (by 35° towards the horizontal, P < 0.001), and resulted in reorientation of the ground reaction force (GRF) vector relative to the femur (from 41° to 82°, P < 0.001). Despite similar strain magnitudes, an overall increase in torsion relative to bending (from 1.70 to 1.95 times bending, P < 0.001) was observed, which was weakly associated with a tendency for increased femoral cross-sectional dimensions (P = 0.1). We suggest that a relative increase in torsion is consistent with a change in femoral posture towards the horizontal, since this change increases the degree to which the bone axis and the GRF vector produce mediolateral long-axis rotation of the bone. These results support the hypothesis that a postural change during early avian evolution could underlie the allometric differences seen between bird and nonavian dinosaur femora by requiring more robust femoral dimensions in birds due to an increase in torsion. J. Morphol. 240:237–249, 1999. © 1999 Wiley-Liss, Inc.