Sauropod CAE (Computer Aided Engineering): kinetic/dynamic and musculoskeletal modeling combined to quantify functional differences in comparison to mammals

计算机辅助工程(CAE)在脊椎动物古生物学中的应用越来越广泛。在软件SIMM®中对复杂的肌肉骨骼系统进行了非常详细的建模，在NASTRAN中使用CAD生命重建对整个灭绝动物进行了运动学/动力学建模，都取得了成功。NASTRAN提供身体各部分或整个动物的重心位置、关节扭矩、动能和势能等数据，并允许优化模拟运动和运动周期，以最大限度地减少能源消耗。SIMM允许详细的3D肌肉重建，预测不同姿势下单个肌肉的瞬间手臂、肌腱长度和其他因素。我们将首次将SIMM模型与新的和现有的NASTRAN模型相结合，通过对两种典型的蜥脚类恐龙的运动和饲养进行建模。这允许导出复杂运动的结果，并显著提高每种建模方法的质量和细节级别。模型将基于保存完好的个体的3D数字骨骼坐骑。分析后的姿势将根据NASTRAN中得出的数据进行选择。建模将以准静态的方式进行(即，在中间站立、最大肢体前伸和后退、直立两足动物姿势)。我们将集中讨论始祖龙尾部肌肉驱动的后肢收缩系统与哺乳动物的不同之处，在哺乳动物的情况下，有几块肌肉使用短力矩的手臂。我们还将对蜥脚类前肢与现存动物(大象和长颈鹿)的前肢进行生物力学建模，以研究肢体长度比例很低(梁龙)或非常高(长颈鹿/腕龙)是如何影响运动的。

Computer Aided Engineering (CAE) is increasingly used in vertebrate paleontology. Both highly detailed modeling of complex musculoskeletal systems in the software SIMM®, and kinetic/dynamic modeling of entire extinct animals using CAD life reconstructions in NASTRAN have been conducted successfully. NASTRAN delivers data such as center of mass position, joint torques, kinetic and potential energy of body segments or the whole animal, and allows optimizing simulated motions and motion cycles for minimal energy use. SIMM allows detailed 3D muscle reconstructions, predicting moment arms, tendon length and other factors for individual muscles in varied poses. We will combine SIMM modeling with new and existing NASTRAN models for the first time by modeling locomotion and rearing of two representative sauropod dinosaurs. This allows deriving results on complex motions , and improving the quality and detail level of each modeling approach significantly. Models will be based on 3D digital skeletal mounts of well preserved individuals. The analyzed postures will be chosen based on data derived in NASTRAN. Modeling will be conducted in a quasi-static approach (i.e. at midstance, maximum limb pro- and retraction, upright bipedal pose). We will focus on the differences between the archosaur M. caudofemoralis driven hind limb retraction system, and the mammalian condition, in which several muscles with short moment arms are employed. We will also model the biomechanics of sauropod forelimbs compared to those of extant animals (elephants and giraffes), to investigate how very low (Diplodocus) or very high (Giraffatitan/Brachiosaurus) limb length ratios influences locomotion.