How to build a dinosaur: musculoskeletal modelling and simulation of locomotor biomechanics in extinct animals

The intersection of paleontology and biomechanics can be reciprocally
illuminating, helping to improve paleobiological knowledge of extinct
species and furthering our understanding of the generality of
biomechanical principles derived from study of extant species. However,
working with data gleaned primarily from the fossil record has its
challenges. Building on decades of prior research, we outline and
critically discuss a complete workflow for biomechanical analysis of
extinct species, using locomotor biomechanics in the Triassic theropod
dinosaur Coelophysis as a case study. We progress from the digital capture
of fossil bone morphology to creating rigged skeletal models, to
reconstructing musculature and soft tissue volumes, to the development of
computational musculoskeletal models, and finally to the execution of
biomechanical simulations. Using a three-dimensional musculoskeletal model
comprising 33 muscles, a static inverse simulation of the mid-stance of
running shows that Coelophysis probably used more upright (extended)
hindlimb postures, and was likely capable of withstanding a vertical
ground reaction force of magnitude more than 2.5 times body weight. We
identify muscle force-generating capacity as a key source of uncertainty
in the simulations, highlighting the need for more refined methods of
estimating intrinsic muscle parameters such as fibre length. Our approach
emphasizes the explicit application of quantitative techniques and
physics-based principles, which helps maximize results robustness and
reproducibility. Although we focus on one specific taxon and question,
many of the techniques and philosophies explored here have much generality
to them, so they can be applied in biomechanical investigation of other
extinct organisms.