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Proc Biol Sci. 2017 Jul 26;284(1859). pii: 20170847. doi: 10.1098/rspb.2017.0847.

Dual function of the pectoral girdle for feeding and locomotion in white-spotted bamboo sharks.

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Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK, USA
Department of Biological Sciences, University of Rhode Island, Kingston, RI, USA.
Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, USA.
Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK, USA.


Positioned at the intersection of the head, body and forelimb, the pectoral girdle has the potential to function in both feeding and locomotor behaviours-although the latter has been studied far more. In ray-finned fishes, the pectoral girdle attaches directly to the skull and is retracted during suction feeding, enabling the ventral body muscles to power rapid mouth expansion. However, in sharks, the pectoral girdle is displaced caudally and entirely separate from the skull (as in tetrapods), raising the question of whether it is mobile during suction feeding and contributing to suction expansion. We measured three-dimensional kinematics of the pectoral girdle in white-spotted bamboo sharks during suction feeding with X-ray reconstruction of moving morphology, and found the pectoral girdle consistently retracted about 11° by rotating caudoventrally about the dorsal scapular processes. This motion occurred mostly after peak gape, so it likely contributed more to accelerating captured prey through the oral cavity and pharynx, than to prey capture as in ray-finned fishes. Our results emphasize the multiple roles of the pectoral girdle in feeding and locomotion, both of which should be considered in studying the functional and evolutionary morphology of this structure.


X-ray reconstruction of moving morphology; cranial elevation; fluoromicrometry; scapulocoracoid; skeletal kinematics; suction expansion

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