Evaluations of bone strength in the evolutionary invasion of land by tetrapods

ended

How tetrapods (vertebrates with digit-bearing limbs) became terrestrial is one of the most transformative yet enigmatic events in vertebrate history that set the stage for the diversification of tetrapods thereafter. Being on land imposes physical demands on the musculoskeletal system and weak bones can severely limit the capabilities of animals, yet the importance of bone strength in the evolution of terrestrial locomotion is not well understood. The proposed research integrates innovative approaches on the limbs of an early stem tetrapod, Ichthyostega, in order to: 1) quantify how well the limb bones in an early stem tetrapod could support locomotion on land, 2) compare the differences between the fore- and hindlimb bone mechanics, and 3) test the prevailing hypothesis that early stem tetrapods walked like extant salamanders. An interdisciplinary synthesis of cutting-edge techniques in engineering, 3D biomedical imaging, palaeontology, and biomechanics will be used to test the structural integrity of fossil limb bones in silico. Bone strength will be quantified with high-resolution μ-CT scans and finite element analysis, an engineering approach to estimate stresses and deformations in complex structures in response to physical demands. This novel dataset will address the ability of Ichthyostega to move on land, and what types of locomotor behaviours were not possible for an early stem tetrapod on land. Simultaneously, training and research activities in state-of-the-art engineering and 3D technology, evolutionary biomechanics, and public outreach will foster the development of the Experienced Researcher (ER) into an innovative and broadly trained researcher and science communicator. At a broader scale, tracing back the evolutionary steps to becoming terrestrial yields powerful insights into the tetrapod body plan, informing how ecological transitions influence functional innovation and how human anatomy is influenced by our ancestry from aquatic tetrapods.