Mud to muscles: Dinosaur-bird locomotor evolution from fossil footprints

化石脚印是运动的直接记录，这是骨骼永远无法做到的。我将使用化石足迹来探索鸟类从兽脚亚目恐龙进化而来的运动变化。与它们的恐龙祖先相比，鸟类的尾巴和相关的肌肉组织要短得多。鸟类是否为了飞行而“放弃”了陆地运动的优势？肢体运动的进化变化是否记录在化石足迹记录中？如果是这样，它们是否表现出从尾巴驱动的兽脚亚目到膝盖驱动的鸟类的逐渐变化，或者肢体运动是否随着特定特征的出现而突然改变？从泥浆到肌肉，我将结合先进的3D成像，物理实验和计算机模拟，以弥合化石足迹和化石骨骼之间的现有差距，揭示这一重要的进化转变。基于实验室的足迹制作实验将结合运动学和动力学分析，以建立一个前所未有的足迹形成的观点。研究人员将利用化石足迹重建灭绝已久的恐龙的肢体运动，然后用超级计算机模拟每一粒沉积物对缩进的脚的反应，来测试重建的运动。这些模拟将计算脚和地面之间发生的力。这些力量和运动将推动肌肉骨骼生物力学模拟，这不仅会揭示恐龙的脚在做什么，而且会揭示这些神秘动物的整个四肢甚至身体曾经是如何移动的。通过对世界各地的化石足迹进行采样，从兽脚亚目恐龙首次出现以来的2.3亿年，该项目将恢复恐龙-鸟类谱系的化石运动。通过严谨、创新的方法，我的提议将解开对灭绝动物运动方式的定量分析，便于与它们现存的后代进行直接比较，并提供一种独特的运动进化视角，这种视角无法仅从骨骼中恢复。

Fossil footprints are a direct record of motion in a way that skeletons can never be. I will use fossil footprints to explore the locomotor changes that took place as birds evolved from theropod dinosaurs. Compared to their dinosaur ancestors, birds have a much-reduced tail and associated musculature. Did birds "give up" terrestrial locomotor superiority in order to fly? Are evolutionary changes in limb motions recorded in the fossil footprint record? If so, do they show a gradual change from tail-driven theropods to knee-driven birds, or do limb motions change abruptly with the appearance of specific traits?From mud to muscles, I will combine advanced 3D imaging, physical experimentation, and computer simulation to bridge the existing gap between fossil footprints and fossil skeletons, shedding light on this important evolutionary transition. Lab-based footprint-making experiments will combine kinematic and kinetic analyses to build an unprecedented view of footprint formation. Limb motions of long-extinct dinosaurs will be reconstructed using fossil tracks, then supercomputer simulations modelling every grain of a sediment responding to the indenting foot will be used to test the reconstructed motions. These simulations will compute the forces occurring between foot and ground. These forces and motions will drive musculoskeletal biomechanical simulations that will shed light, not only on what the feet of dinosaurs were doing, but on how the whole limbs and even bodies of these enigmatic animals once moved.By sampling fossil tracks from around the world, spanning the 230 million years since theropods first appeared, this project will recover fossilised motions along the dinosaur-bird lineage. Using rigorous, innovative methods, my proposal will unlock quantitative analysis of the way extinct animals moved, facilitating direct comparison with their extant descendants, and providing a unique view of locomotor evolution that cannot be recovered from bones alone.