School of Science and Engineering, University of Sunshine Coast, Sippy Downs, Queensland 4556, Australia
School of Biological Sciences, The University of Queensland, Queensland 4072, Australia.
J R Soc Interface. 2018 Sep 26;15(146):20180276. doi: 10.1098/rsif.2018.0276.
Certain lizards are known to run bipedally. Modelling studies suggest bipedalism in lizards may be a consequence of a caudal shift in the body centre of mass, combined with quick bursts of acceleration, causing a torque moment at the hip lifting the front of the body. However, some lizards appear to run bipedally sooner and for longer than expected from these models, suggesting positive selection for bipedal locomotion. While differences in morphology may contribute to bipedal locomotion, changes in kinematic variables may also contribute to extended bipedal sequences, such as changes to the body orientation, tail lifting and changes to the ground reaction force profile. We examined these mechanisms among eight Australian agamid lizards. Our analysis revealed that angular acceleration of the trunk about the hip, and of the tail about the hip were both important predictors of extended bipedal running, along with increased temporal asymmetry of the ground reaction force profile. These results highlight important dynamic movements during locomotion, which may not only stabilize bipedal strides, but also to de-stabilize quadrupedal strides in agamid lizards, in order to temporarily switch to, and extend a bipedal sequence.
某些蜥蜴被发现可以用两条腿奔跑。建模研究表明，蜥蜴的两足运动可能是身体质心在尾部发生转移的结果，加上快速的加速爆发，在臀部产生一个抬起身体前部的扭矩。然而，一些蜥蜴似乎比这些模型预期的更早、更长时间地以两足形式奔跑，这表明两足运动是一种积极的选择。虽然形态上的差异可能有助于两足运动，但运动学变量的变化也可能有助于延长两足序列，例如改变身体姿势、抬起尾巴和改变地面反作用力分布。我们在 8 种澳大利亚鬣蜥中研究了这些机制。我们的分析表明，躯干相对于臀部的角加速度和尾巴相对于臀部的角加速度都是延长两足奔跑的重要预测因素，同时地面反作用力分布的时间不对称性也增加了。这些结果突出了运动过程中的重要动态运动，这些运动不仅可以稳定两足步幅，还可以使鬣蜥的四足步幅不稳定，从而暂时切换到并延长两足序列。
