Loïc, Kéver;
Olivier, Damien;
Marghoub, Arsalan;
Evans, Susan E;
Vickaryous, Matthew K;
Moazen, Mehran;
Herrel, Anthony;
(2022)
Biomechanical behaviour of lizard osteoderms and skin under external loading.
Journal of Experimental Biology
, 225
(20)
, Article jeb244551. 10.1242/jeb.244551.
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Abstract
Many species of lizards are partially enveloped by a dermal armour made of ossified units called osteoderms. Lizard osteoderms demonstrate considerable species-specific variation in morphology and histology. Although a physical/protective role (against predators, prey, conspecifics, and impact loading during falls) is frequently advanced, empirical data on the biomechanics of lizard osteoderms are scarce, limiting our understanding of form-function relationships. Here, we report deformation recorded at the surface of temporal osteoderms during controlled external loading of preserved specimens of eleven lizard species (Tiliqua rugosa, Tiliqua scincoides, Corucia zebrata, Pseudopus apodus, Timon lepidus, Matobosaurus validus, Broadleysaurus major, Tribolonotus gracilis, Tribolonotus novaeguineae, Heloderma horridum and Heloderma suspectum). Based on the strains recorded in situ and from isolated osteoderms, the skin of the species investigated can be ranked along a marked stiffness gradient that mostly reflects the features of the osteoderms. Some species like Tiliqua rugosa and the two Heloderma species had very stiff osteoderms and skin while others like Timon lepidus and Pseudopus apodus were at the other end of the spectrum. Histological sections of the osteoderms suggest that fused (vs. compound) osteoderms with a thick layer of capping tissue are found in species with a stiff skin. In most cases, loading neighbouring osteoderms induced large strains in the instrumented osteoderm attesting that, in most species, lizard osteoderms are tightly interconnected. These data empirically confirm that the morphological diversity observed in lizard osteoderms is matched by variability in biomechanical properties.
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