Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912;
Center for Movement Studies, Kennedy Krieger Institute, Baltimore, MD 21205.
Proc Natl Acad Sci U S A. 2021 Feb 16;118(7). doi: 10.1073/pnas.2023513118.
Reconstructions of movement in extinct animals are critical to our understanding of major transformations in vertebrate locomotor evolution. Estimates of joint range of motion (ROM) have long been used to exclude anatomically impossible joint poses from hypothesized gait cycles. Here we demonstrate how comparative ROM data can be harnessed in a different way to better constrain locomotor reconstructions. As a case study, we measured nearly 600,000 poses from the hindlimb joints of the Helmeted Guineafowl and American alligator, which represent an extant phylogenetic bracket for the archosaurian ancestor and its pseudosuchian (crocodilian line) and ornithodiran (bird line) descendants. We then used joint mobility mapping to search for a consistent relationship between full potential joint mobility and the subset of joint poses used during locomotion. We found that walking and running poses are predictably located within full mobility, revealing additional constraints for reconstructions of extinct archosaurs. The inferential framework that we develop here can be expanded to identify ROM-based constraints for other animals and, in turn, will help to unravel the history of vertebrate locomotor evolution.
对已灭绝动物运动的重建对于我们理解脊椎动物运动进化中的主要转变至关重要。关节活动范围 (ROM) 的估计值长期以来一直被用于从假设的步态周期中排除解剖上不可能的关节姿势。在这里，我们展示了如何以不同的方式利用比较 ROM 数据来更好地限制运动重建。作为一个案例研究，我们测量了盔头鸡和美洲鳄后肢关节的近 60 万个姿势，它们代表了恐龙祖先及其 pseudosuchian（鳄鱼线）和 ornithodiran（鸟类线）后代的现存系统发育支架。然后，我们使用关节活动性映射来搜索全关节活动性和运动过程中使用的关节姿势子集之间的一致关系。我们发现，行走和奔跑姿势可预测地位于全活动性范围内，这为已灭绝恐龙的重建提供了额外的限制。我们在这里开发的推理框架可以扩展到为其他动物确定基于 ROM 的限制，进而有助于揭示脊椎动物运动进化的历史。
