Under pressure: morphological and ecological correlates of bite force in the rock-dwelling lizards Ouroborus cataphractus and Karusasaurus polyzonus (Squamata: Cordylidae)

Rock-dwelling lizards are hypothesized to be highly constrained in the evolution of head morphology and, consequently, bite force. Because the ability to generate a high bite force might be advantageous for a species' dietary ecology, morphological changes in head configuration that allow individuals to maintain or improve their bite force under the constraint of crevice-dwelling behaviour are to be expected. The present study addressed this issue by examining head morphology, bite force, and a number of dietary traits in the rock-dwelling cordylid lizards Ouroborus cataphractus and Karusasaurus polyzonus. The results obtained show that O. cataphractus has a larger head and higher bite force than K. polyzonus. In K. polyzonus, head width, lower jaw length, and jaw closing-in lever are the best predictors of bite force, whereas head height is the main determinant of bite force in O. cataphractus. Although the observed difference in bite force between the species does not appear to be related to dietary patterns or prey handling, the prey spectrum available for intake was greater in O. cataphractus compared to K. polyzonus. We discuss the influence of interspecific differences in anti-predator morphology on head morphology and bite force in these rock-dwelling species. (c) 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111, 823-833.