Reconstructing the lost cartilaginous epiphyses in extinct archosaurs' limbs

运动是四足动物进化成功的最重要的功能之一。要了解当前物种的运动是如何进化的，就意味着要研究它们的化石记录。进化生物力学通过观察灭绝生物的现存亲属来估计它们的运动能力，从而解决了这个问题。人们特别努力推断非鸟类恐龙和其他已灭绝的祖龙的运动方式。然而，与其他大多数四足动物一样，祖龙的肢骨有软骨骨骺，但不会骨化。这导致在对这些动物进行生物力学分析时存在很高的不确定性。令人惊讶的是，矫正策略仍然相当主观和简单，未能提出一个强大的方法来解释缺失的软骨。在这里，我建议回答这个关键问题，具体重建已灭绝的祖龙的丢失的CarTilaginous骨骺，使用尖端的定量方法。以股骨为重点，将利用大样本初龙的三维特征来估计化石物种缺失的骨骺。随后的现代形态多样性的研究，我将开发的协议，评估其准确性，重建骨骺在现有物种的控制虚拟实验。我还将强调对采样变异性的鲁棒性，以给出重建的置信度。最后，重建的影响将进行比较生物力学分析进行测试。在定量脊椎动物古生物学，进化生物学和生物力学的交叉点上，该项目旨在开发迄今为止最客观，最可靠的方法来重建灭绝的祖龙中丢失的骨骺。该项目前所未有的成果应该会深刻影响关于灭绝的祖龙如何灭绝的推论，并将打开视角，将这种方法推广到任何其他四足动物群。

Locomotion is among the most important function involved in tetrapod evolutionary success. Understanding how locomotion in current species evolved implies to study their fossil record. Evolutionary biomechanics tackles this topic, by estimating locomotor abilities of extinct organisms by observing their extant relatives. Particular efforts have been made to infer the locomotion in non- avian dinosaurs and other extinct archosaurs. However, as in most other tetrapods, archosaur limb bones have cartilaginous epiphyses that do not fossilise. This leads to high levels of uncertainty when conducting biomechanical analyses on such animals. Surprisingly, corrective strategies remained rather subjective and simplistic, failing to propose a robust way to account for missing cartilage. Here I propose to answer to this critical issue by concretely REconstructing the LOst CArTilaginous Epiphyses of extinct archosaurs, using cutting-edge quantitative methods. Focusing on the femur, the three-dimensional characteristics of a large sample of archosaurs will be used to estimate the missing epiphyses of fossil species. Subsequently to the study of modern morphological diversity, I will develop the protocol by assessing its accuracy to reconstruct epiphyses in a controlled virtual experimentation on extant species. I will also stress robustness to sampling variability to give the degree of confidence to put on the reconstruction. Finally, the impact of reconstructions will be tested by conducting a comparative biomechanical analysis. At the crossroads of quantitative vertebrate palaeontology, evolutionary biology and biomechanics, the project ambitions to develop the most objective and reliable way to date to reconstruct the lost epiphyses in extinct archosaurs. The unprecedented outcomes of the project should deeply impact inferences about how extinct archosaurs could locomote, and will open perspectives to generalise the approach to any other tetrapod group.