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.

The Middle Triassic procolophonid Kapes bentoni: computed tomography of the skull and skeleton

“…In life, it was probably curved to form an arc fitting around the side of the somewhat curved rib cage, as observed in modern lizards (e.g. Tinius & Russell ). The right coracoid is rotated by 45° relative to the scapula, probably because of the deformation that affected the whole specimen (Fig.…”

“…The existence of a cartilaginous suprascapula is possible, as the distal edge of the scapular blade is straight and is like the margin seen in recent lizards with a suprascapula (e.g. Tinius & Russell ). Säilä () also reported a rugose distal margin of the scapular blade in Leptopleuron , so it is possible that a cartilaginous suprascapular was present in procolophonids.…”

What is bred in the bone: Ecomorphological associations of pelvic girdle form in greater Antillean Anolis lizards

“…The hypoischium continues posteriorly from the ischiadic symphysis as an elongated triangle ( Figure 4c). In prepared skeletal material, the proischiadic cartilage contacts the epipubis, thus closing the thyroid fenestra (Russell & Bauer, 2008;Tinius, 2016), but this is not evident in the CT images ( Figure 4c).…”

“…The anoline ecomorph concept is predicated upon observations that island anoles of the Caribbean occupying similar ecological niches exhibit similar morphological features, regardless of their phylogenetic relationship or biogeographic distribution (Losos, ; Losos et al, ; Williams, ). Given the demonstrable external morphological convergence and niche partitioning among island anoles (Buckley & Roughgarden, ; Kolbe et al, ; Losos et al, ; Mahler et al, ), resulting from diversification in similar environments (Mahler et al, ), we predict that ecomorphological signatures will be present in skeletal (and muscular) attributes associated with their locomotion in the distinctive parts of the structural habitat that they exploit (Anzai et al, ; Tinius & Russell, ). Beyond the field notes of Peterson (), however, few authors have explored such potential ecomorphological differences in the 3D form of the postcranial skeleton and musculature of anoles.…”

“…We describe the variability in the morphology of the pelvic girdle in situ for two outgroup taxa and 26 anole species that represent four distinctive ecomorphs (trunk-ground, trunk-crown, crown-giant, twig). Based on the results of previous studies (Legreneur et al, 2012;Mahler et al, 2013;Tinius & Russell, 2014), these ecomorphs are expected to exhibit distinctive, but subtle, differences in locomotor mechanics. We investigate if these differences are reflected in the 3D configuration of the pelvic girdle.…”