Broyde Sarah, Dempsey Matthew, Wang Linjie, Cox Philip G, Fagan Michael, Bates Karl T
Department of Musculoskeletal Biology, Institute of Aging and Chronic Disease, University of Liverpool, The William Henry Duncan Building, 6 West Derby Street, Liverpool L7 8TX, UK.
Department of Engineering, University of Hull, Hull HU6 7RX, UK.
Proc Biol Sci. 2021 Feb 24;288(1945):20202809. doi: 10.1098/rspb.2020.2809. Epub 2021 Feb 17.
Biomechanical modelling is a powerful tool for quantifying the evolution of functional performance in extinct animals to understand key anatomical innovations and selective pressures driving major evolutionary radiations. However, the fossil record is composed predominantly of hard parts, forcing palaeontologists to reconstruct soft tissue properties in such models. Rarely are these reconstruction approaches validated on extant animals, despite soft tissue properties being highly determinant of functional performance. The extent to which soft tissue reconstructions and biomechanical models accurately predict quantitative or even qualitative patterns in macroevolutionary studies is therefore unknown. Here, we modelled the masticatory system in extant rodents to objectively test the ability of current muscle reconstruction methods to correctly identify quantitative and qualitative differences between macroevolutionary morphotypes. Baseline models generated using measured soft tissue properties yielded differences in muscle proportions, bite force, and bone stress expected between extant sciuromorph, myomorph, and hystricomorph rodents. However, predictions from models generated using reconstruction methods typically used in fossil studies varied widely from high levels of quantitative accuracy to a failure to correctly capture even relative differences between macroevolutionary morphotypes. Our novel experiment emphasizes that correctly reconstructing even qualitative differences between taxa in a macroevolutionary radiation is challenging using current methods. Future studies of fossil taxa should incorporate systematic assessments of reconstruction error into their hypothesis testing and, moreover, seek to expand primary datasets on muscle properties in extant taxa to better inform soft tissue reconstructions in macroevolutionary studies.
生物力学建模是一种强大的工具，可用于量化已灭绝动物功能表现的演变，以了解推动主要进化辐射的关键解剖学创新和选择压力。然而，化石记录主要由硬体部分组成，这迫使古生物学家在这类模型中重建软组织特性。尽管软组织特性对功能表现具有高度决定性，但这些重建方法在现存动物上很少得到验证。因此，在宏观进化研究中，软组织重建和生物力学模型准确预测定量甚至定性模式的程度尚不清楚。在这里，我们对现存啮齿动物的咀嚼系统进行建模，以客观测试当前肌肉重建方法正确识别宏观进化形态型之间定量和定性差异的能力。使用测量的软组织特性生成的基线模型在现存松鼠型、鼠型和豪猪型啮齿动物之间产生了预期的肌肉比例、咬合力和骨应力差异。然而，使用化石研究中常用的重建方法生成的模型预测差异很大，从高度的定量准确性到甚至无法正确捕捉宏观进化形态型之间的相对差异。我们的新实验强调，使用当前方法在宏观进化辐射中正确重建类群之间的定性差异具有挑战性。未来对化石类群的研究应在假设检验中纳入对重建误差的系统评估，此外，应寻求扩大现存类群肌肉特性的主要数据集，以便为宏观进化研究中的软组织重建提供更好的信息。
