Lizards under pressure: skull nanoindentation in an insular reptile for palaeobiological inference

Abstract

Computational approaches are increasingly used to study the relationship between form and function in extinct and living organisms. However, one major challenge remains: assumptions about bone material properties, especially when studying fossils. In this work, direct mechanical testing and computer-based modelling are combined to assess cranial bone stiffness in the lizard genus Gallotia , endemic to the Canary Islands (Spain), including extinct species. Using linear mixed models, bone stiffness was found to be uniform across skull regions, with a trend towards lower stiffness in larger species. Simulations of biting loads showed that differences in bone properties had a limited influence on mechanical performance, supporting the use of average values in functional models. Using this framework, bone stiffness in extinct Gallotia giants was estimated, and its significance was explored. The results suggest a link between skull flexibility, body size, and diet, offering a practical approach to reconstructing biomechanical traits in extinct vertebrates across evolutionary timescales.