The evolution of quadrupedal gaits: calculating limb phase and simulating limb movements based on fossil trackways

Quadrupedal trackways offer rare direct evidence of locomotion in extinct tetrapods, yet reconstructing limb phase—the timing relationship among the four limbs—has long been limited by unknown trackmaker size. This project advances a refined regression‑based method that infers limb phase from stride‑length variation alone, modelling theoretical stride–phase relationships through a constrained family of lines. The approach is more robust, intuitive, and applicable across the full gait spectrum, while also enabling automated identification of pes‑and‑manus_tracks, coupling values, and trunk length. Validation will combine numerical simulations, Icelandic horse experiments, and extensive datasets from sprawling tetrapods such as salamanders, iguanas, and caimans, recorded via integrated photogrammetry and videogrammetry. A complementary machine‑learning model trained on hundreds of sauropod trackways will improve noise handling and allow average gait estimation from short or low‑quality sequences. A dedicated animation tool will further test biomechanical plausibility by simulating reconstructed gaits and trackways. Together, these innovations will enable the first systematic reconstruction of gaits across major extinct tetrapod groups, providing new insights into the evolution of quadrupedal_locomotion and the factors shaping gait selection through deep time.