Geometric Morphometric Analysis of the Breast‐Shoulder Apparatus of Lizards: A Test Case Using Jamaican Anoles (Squamata: Dactyloidae)

Abstract

The breast-shoulder apparatus (BSA) is a structurally and kinematically complex region of lizards. Compared with the pelvic region it has received little attention, even though its morphological variation is known to be extensive. This variability has seldom been the focus of functional explanation, possibly because the BSA has been difficult to explore as a composite entity. In this study we apply geometric morphometric techniques to the analysis of the BSA in an attempt to more fully understand its configuration in relation to differential use in locomotion. Our approach centers upon the Jamaican radiation of anoline lizards (genus Norops) as a tractable, small monophyletic assemblage consisting of species representing several ecomorphs. We hypothesized that the different species and ecomorphs would exhibit variation in the configuration of the BSA. Our findings indicate that this is so, and is expressed in the component parts of the BSA, although it is subtle except for Norops valencienni (twig ecomorph), which differs greatly in morphology (and behavior) from its island congeners. We further found similarities in the BSA of N. grahami, N. opalinus (both trunk-crown ecomorphs), and N. garmani (crown giant). These outcomes are promising for associating morphology with ecomorphological specialization and for furthering our understanding of the adaptive response of the BSA to demands on the locomotor system.