This study evaluates the loads on the limb bones of the tiger salamander (Ambystoma tigrinum) and the Argentine black and white tegu (Tupinambus merianae) during terrestrial locomotion using three-dimensional measurements of the ground reaction force (GRF) and hindlimb kinematics, anatomical measurements of the femur and hindlimb muscles, and in vivo measurements of bone strain (tegus only). Peak tensile bending stresses in the femur were generally below 15 MPa, which is fairly low compared to observations from other vertebrate lineages. Using mechanical property values collected from hardness tests, femoral safety factors were calculated to be greater than 12 for both taxa, much higher than those seen in birds or mammals (which range from 2 to 4). This was due mainly to lower levels of locomotor stresses rather than any difference in mechanical properties of the bone. Together with data from other amphibian and reptile lineages, these results suggest that low magnitude loading and high limb bone safety factors may have an ancient evolutionary history.However, limb bones can generally resist much higher loads than they normally experience. ... insurance against damage or failure, they could also add extra energetic cost to limb bone growth, maintenance, and transport (Diamond, 1998).
|Title||:||Loading Mechanics in Femora of Tiger Salamanders (Ambystoma Tigrinum) and Tegu Lizards (Tupinambus Merianae): Implications for the Evolution of Limb Bone Design|
|Author||:||Kathryn Megan Wright|
|Publisher||:||ProQuest - 2008|