Fortbewegung und funktionelle Morphologie des Bewegungsapparates vom Zweifinger-Faultier (Choloepus didactylus)

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The overarching goals of the proposed research are 1) a contribution to a better understanding of the kinematics and kinetics of locomotion in arboreal mammals in general, 2) a more detailed understanding of the influence of gravity on locomotion and linked musculoskeletal adaptations and 3} a more complete, evolutionary understanding of the convergent evolution of suspensory quadrupedal locomotion in two- and three-toed sloths.Biplane high-speed x-ray videography makes three-dimensional movements of proximal limb segments during locomotion visible. Comparisons of kinematic parameters of suspensory quadrupedal locomotion to both, arboreal quadrupeds (data from our own lab) and brachiators (literature) will enable a fuller comprehension of this specific mode of arboreal locomotion. Kinematic data will additionally be used to realistically animate CT-scan derived 3Dreconstructions of the skeleton. Animated reconstructions like these will be crucial for inferring locomotion in fossil forms in future projects.The kinematic description of limb movements, accurate measurements on mass distribution in the limb segments and substrate reaction forces obtained will facilitate inverse-dynamics analysis (IDA). IDA enables experimental validation of several hypotheses on the loading regime and joint torques during suspensory quadrupedal locomotion of sloths. Fibre-type composition and possible functional regionalisation within the muscles involved in locomotion of two-toed sloths will be described and compared to functional relationships of muscle-architecture described in the literature for arboreal and terrestrial mammals. The synthetic approach outlined here will illuminate different aspects of the morphofunction of sloths within mammals to enable a coherent discussion of the evolution of their unusual locomotor behaviour.