Furcula Diversity Within the Avian Flight Apparatus

A major unknown in avian biology is the morphological basis of flight style diversity. While certain aspects pectoral anatomy, such as an enlarged sternum and hypertrophied muscles, clearly relate to aerial locomotion general, finer details form-function correspondence are less apparent. Nevertheless, furcula shape has been used infer extinct avians because cranial origin largest muscle, m. pectoralis, most extant birds. However, previous studies, which examined isolation, indicate only a modest correlation between style. We hypothesized that relationship may be heavily mediated by other particularly orientation muscle morphology. computed tomography digital dissection techniques collect situ data on large (n=108) diverse (21 orders) sample formalin-fixed specimens. some specimens required addition Lugol's iodine visualize soft tissue, did not require contrast enhancement permit bone reconstruction. found moderate consistent with studies (e.g., soaring birds have flatter, more V-shaped furculae), however magnitude differences taxonomic categories was smaller, perhaps due different measurement techniques. Novel measures furcular girdle revealed larger, slower-flapping tend cranially-positioned furculae, greater need for wing protraction via pectoralis. Further, centers-of-mass main muscles laterally-bowed furculae. In measures, hummingbirds group similar mass or shape, likely owing their kinematically-unique Overall, our findings recommend caution inferring from alone. Rather, better viewed part larger functional unit including sternum, coracoids, muscles.