Meeting Abstract

P2-115   -   Biomechanical characterisation lizard osteoderms Marghoub, A*; Kéver, L; Williams, C; Rai, S; Abzhanov, A; Vickaryous, M; Herrel, A; Evans, S E; Moazen, M; University College London, London, UK; National Museum of Natural History, Paris, France; University of Guelph, 50 Stone Road East, Guelph, ON, Canada; Imperial College London, Silwood Park Campus, Berkshire, U.K; Imperial College London, Silwood Park Campus, Berkshire, U.K; University of Guelph, 50 Stone Road East, Guelph, ON, Canada; National Museum of Natural History, Paris, France; University College London, London, UK; University College London, London, UK arsalan.biomech@gmail.com

Osteoderms (ODs) are calcified tissues that develop within the skin of many lizard species. Not only their morphological and histological properties are different, they may also appear in different parts of the body. Some lizards may have ODs only on the head, some on the dorsum, some all over the body, and some may not have it. To investigate the reasons behind this diversity, and their effect on the functions of the ODs, several methods were used to study the biomechanical properties of the ODs in five species (Corucia zebrata, Timon Lepidus, Heloderma suspectum, Ophisaurus ventralis, and Varanus komodoensis). Histological sectioning combined with micro-CT scanning and digital microscopy were used to investigate the internal structure of single ODs. Then mechanical properties of different regions were investigated using nanoindentation. Finally, finite element method was used to investigate the effect of shape and form under mechanical loading, simulating the loads that occur in nature. Frontal and mandible bones, and dental tissue of the same species were also studied to compare the mechanical properties of ODs with bone and teeth. The imaging and nanoindentation results showed that ODs are mainly composed of two main types of tissue: the capping tissue, which may not exist in some of the ODs (such as Timon Lepidus), and the bony tissue underneath. The capping tissue in usually harder than bony tissue. In some ODs slightly harder and in some significantly harder (the elastic modulus can be close to the Enamel in tooth). Finite element modelling showed that Corucia zebrata OD is more flexible than all other ODs. These differences in the structural and mechanical properties can be the result of different roles that ODs play in each species, whether they are acting as a protective shield against predators, against heat, or other environmental factors, and/or their role in locomotion.