Meeting Abstract
The avian wishbone, or furcula, is formed by a fusion of paired clavicles and/or a modified interclavicle, variably connects to the coracoid and sternum, and serves as the cranial-most attachment of the m. pectoralis in most birds. Although several overlapping functional hypotheses have been proposed for furcular morphology, both static (related to posture and support) and dynamic (related to flight style and respiration), the bone remains an enigmatic part of the avian pectoral girdle. In particular, we have little understanding of the element’s substantial variation among birds in its overall shape, cross-section, mechanical properties, and associated soft tissues. Despite the hypothesized significance of the furcula in the origin of flight and diversification of flight styles, much further work needs to be done to characterize its functional properties among extant taxa. We used contrast-enhanced CT imaging, joint histology, and digital muscle fiber orientation reconstruction to comprehensively investigate the structure and function of the furcula in the European starling (Sturnus), budgerigar (Melopsittacus), and domestic chicken (Gallus). Both starlings and budgerigars are small, intermittent-flapping fliers (as opposed to continuous-flapping and soaring fliers) that predominantly utilize flap-gliding and flap-bounding, respectively. Chickens, on the other hand, are poor fliers despite their well-developed pectoral musculature. We found marked differences in muscle attachments, muscle fiber orientation, and ligamentous soft tissues consistent with flight style variation in our sample. These results will form the basis of future comparative studies aiming to examine the functional relevance of bird pectoral anatomy to the evolution of the clade.
