Meeting Abstract
Mammal crania are characterized by steep strain gradients across the skull. During feeding frontal and parietal bones experience very low strains compared with the maxilla, mandible and zygomatic arch. This suggests that the top of the mammal cranium is not optimized for dissipating feeding forces, where optimality is defined as maximum strength with minimum material. In order to determine whether strain gradients are also seen in lizards, we documented variation in in vivo strain magnitudes across the crania of at least 3 individuals of Tupinambis merianae, Anolis equestris, Gecko gecko, and Iguana iguana during bite force transducer biting and, in some cases, feeding. Rosette strain gages were placed in various combinations on frontal, parietal and maxilla, principal strains calculated, and nested ANOVAs were conducted to examine the effects of gage location, bite point, and individual on maximum and minimum principal strain magnitudes within each species, with bite force included as a covariate. Factors of gage location and bite point were nested within individuals. Results reveal that individual effects on principal strain magnitudes are small or not significant, in contrast to large effects of gage location and bite point. Lizards experience much higher strains on top of the cranium (frontal and parietal) than recorded from homologous sites in mammals. These results reveal that mammal and lizard crania are under different design constraints, with lizard crania being better designed (maximum strength with minimum material) for dissipating feeding forces than mammals. Funding was provided by joint BBSRC grants to M. F. and S.E. (BB/H011668/1 and BB/H011854/1), a research grant of the Research Foundation – Flanders (FWO) to A.H
