Data from: Associated evolution of bipedality and cursoriality among Triassic archosaurs: a phylogenetically controlled evaluation.

Bipedalism evolved more than twice among archosaurs, and it is a characteristic of basal dinosaurs and a prerequisite for avian flight. Nevertheless, the reasons for the evolution of bipedalism among archosaurs have barely been investigated. Comparative analysis using phylogenetically independent contrasts showed a significant correlation between bipedality (relative length of forelimb) and cursoriality (relative length of metatarsal III) among Triassic archosaurs. This result indicates that, among Triassic archosaurs, bipeds could run faster than quadrupeds. Bipedalism is probably an adaptation for cursoriality among archosaurs, which may explain why bipedalism evolved convergently in the crocodilian and bird lineages. This result also indicates that the means of acquiring cursoriality may differ between archosaurs and mammals.双足行走在初龙类（archosaurs）中独立演化的次数超过两次，且该特征是基干恐龙（basal dinosaurs）的标志性性状，同时也是鸟类飞行演化的必要前提。然而，学界针对初龙类为何会演化出双足行走习性的相关研究却极为匮乏。通过系统发育独立对比（phylogenetically independent contrasts）开展的比较分析显示，三叠纪时期的初龙类中，双足运动相关特征（前肢相对长度）与奔跑能力（第三跖骨相对长度）之间存在显著相关性。该结果表明，在三叠纪初龙类类群中，双足动物的奔跑速度显著快于四足动物。双足行走大概率是初龙类适应奔跑需求的演化策略，这或许可以解释为何双足行走在鳄类与鸟类支系中发生了趋同演化。此外，该研究结果还揭示，初龙类与哺乳类获取奔跑能力的演化路径可能存在差异。