Evolution of the crocodylian forelimb: Anatomy, biomechanics, and functional morphology

The terrestrial locomotor behavior of crocodylians is unique among extant tetrapods due to the variability in limb postures that the many taxa are capable of assuming. Given that the ancestors of extant crocodylians likely adopted parasagittal limb postures and were primarily terrestrial cursors, crocodylians represent an unique opportunity to examine the effects of major locomotor transformations on anatomy and functional morphology, brought about by adaptation to amphibious modes of life in this case.; In order to better understand functional analyses of the crocodylian forelimb, the soft-tissue anatomy of this region was examined for a phylogenetically diverse sample of crocodylians, representing the first time the anatomy of the forelimb has been fully documented in the literature. Assessment of the evolution of terrestrial locomotion within Crocodylia was accomplished through examination of several biomechanical properties in a phylogenetic context. Torsion of the humerus, articular morphology, and cross-sectional properties were analyzed using a variety of techniques. Relatively terrestrial crocodylian species can be distinguished from more aquatic species via several quantifiable properties, and captive specimens are distinct from wild ones. Cross-sectional geometric properties do not, however, reflect locomotor behavior, suggesting that resorption and remodeling rates are insufficient to reflect interspecific differences.; The evolution of terrestrial locomotion among crocodylians is characterized by several independent adaptations to increased locomotor efficiency as well as reductions in efficiency in some lineages.