Amphisbaenians, a group of fossorial lizards, display remarkable musculoskeletal adaptations that enable efficient burrowing in diverse ecological contexts. This project aims to uncover how their musculoskeletal system evolved and modulates its components to optimize performance, using a multiscale, interdisciplinary approach. Central to this effort are eight complementary hypotheses, each investigated by partner laboratories through integrated methodologies. At the cranial level, we test whether variation in skull morphology reflects functional specialization between regions (HP1), and whether macro-scale skull shapes are optimized to withstand environmental and feeding-related mechanical loads (HP2). At the system level, we assess correlations between burrowing and biting forces (HP3), and explore the developmental and genetic underpinnings of cranial variation (HP4). At the tissue and material level, we investigate how genetic and biomechanical variation is expressed in the nano-structure of bones, cartilages, and sutures (HP5), and how material composition and structure influence biomechanical performance (HP6). At the organ and whole-body level, we examine how variation in skeletal tissues co-evolves with that of soft tissues such as muscles (HP7), and how alternative head-first burrowing modes are achieved through conserved motor patterns combined with divergent head movements (HP8). By integrating imaging, in vivo experimentation, computer simulations, molecular analyses, and motion reconstruction across scales—from genes and nano-structures to organismal behavior—this project will provide unprecedented insights into the evolutionary morphology of amphisbaenians. Beyond advancing fundamental understanding of vertebrate adaptation, it will establish a powerful framework for linking multiscale biological data to performance and ecology.