Evolution of intervertebral form and function in Crocodylomorpha

Several recent studies have delved into the functional (biomechanics) and morphological
(complexity, heterogeneity) high variability of the mammalian axial skeleton, developing novel techniques for functional data acquisition through digital modelling. However, Crocodylomorpha has received little attention comparatively, despite a 230 my long evolutionary history and adaptability across a variety of environments resulting in a wide range of morphologies and diets. Extant crocodylians display almost the entire range of quadrupedal gaits found in mammals, and studies centred on their axial skeleton procoelous) have highlighted both its functional and morphological disparity. However the modality and underlying mechanisms enabling those innovations remain unclear, overshadowing our understanding of the functional evolution of the crocodylomorph
axial skeleton. Here, we examine the influence of vertebral as well as osteoderm morphology over joint function and their impacts on locomotory behaviours using key crocodylomorph taxa. We present our preliminary results reconstructing the evolution of the biomechanical form and function of the axial skeleton throughout Crocodylomorpha in light of inferred habitat preferences. Through the use of experimentally validated digital joint mobility analyses (AutoBend software), we underline variations in mechanical properties (osteological range of motion and joint stiffness) along the presacral axial skeleton of iconic members of Crocodylomorpha. We investigate how these fluctuations dictate potential locomotory behaviours and how they correlate with inferred habitats
and morphological variations. Our results show that the neck is less mediolaterally mobile than sagittally in aquatic and semiaquatic crocodylomorphs, and reaches greatest ranges of motions in highly aquatic forms. In terrestrial taxa, the neck and the middle portion of the dorsal region show a marked drop in mobility. In the thoracic region, aquatic crocodylomorphs display greater mediolateral bending and axial rotation (increasing posteriorly) than terrestrial crocodylomorphs which show greater ventral flexion only. The anterior thoracic region in aquatic taxa is distinct through a shift of bending properties, unlike terrestrial crocodylomorphs which tend to increase mediolateral and sagittal flexion.