Employing C-T Scanning to Explore Anatomy
Rationale
The pectoral limb and girdle play important roles in the locomotion of lizards, and their form is likely related to patterns of ecological diversity. The forelimbs connect indirectly to the axial skeleton through a multi-joint complex that constitutes the breast-shoulder apparatus (BSA), comprised of the scapula, coracoid, clavicle, interclavicle, sternum and rib cage (fig. 1 a). This arrangement permits a greater range of motion of the limb girdle on the body wall than is evident in the more direct linkage between the pelvic girdle and vertebral column (fig. 1 b). An exploration of the structural and functional-morphological variability of the BSA in situ will enable enhanced interpretation of its anatomical form. This contribution focuses on the morphological variability of the clavicle.
Figure 1: Display of the skeletal elements of the pectoral and pelvic region of Eublepharis. The two girdles differ greatly in the number of constituent parts and the mobility between them.
Methods
Computed tomography (CT) allows for visualization of in situ relationships of anatomical features. CT of the BSA allows assessment of the morphological diversity shown by its constituent parts. For this study 19 preserved lizards were scanned in a Skyview microCT and the resulting CT images were compiled and analyzed using “Avizo”. For this investigation we isolate and explore the morphology of the clavicle.
We address the following questions:
1) What is the 3D variability of form of clavicle of lizards?
2) How might this variation be related to function?
All image series depict the left clavicle in anterior, left lateral and ventral perspective. Registration points relating to other components of the BSA are represented by dots: the vertebral column, the tip of the lateral process of the interclavicle (lt icl), the anterior tip of the interclavicular-sternal joint (icl-st), the anterior tip of the scapula-suprascapular joint (sc-ssc), and the anterior intersection point between the scapula and coracoid at the glenoid (ant gl).
