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.初龙类（archosaurs）的两足行走习性演化次数超过两次，它是基干恐龙的特征，同时也是鸟类飞行的必要前提条件。然而，学界针对初龙类演化出两足行走习性的原因却鲜有研究。通过系统发育独立对比（phylogenetically independent contrasts）开展的比较分析显示，三叠纪初龙类的两足性（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，在三叠纪初龙类中，两足行走动物的奔跑速度快于四足行走动物。两足行走习性大概率是初龙类适应奔跑能力的演化策略，这或许可以解释为何两足行走在鳄类和鸟类支系中独立演化出现。该结果还表明，初龙类与哺乳类获取奔跑能力的方式可能存在差异。