The appendicular skeleton of the Early Permian genusLabidosaurus(Reptilia, Captorhinomorpha, Captorhinidae) and the hind limb musculature of captorhinid reptiles

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Abstract
The appendicular skeleton of the Early Permian captorhinid reptile Labidosaurus hamatus is described and figured. The pectoral girdle is heavily constructed, with a glenoid fossa that limited the humerus to an excursion arc of approximately 50 degrees. The humerus has a small but distinct supinator process and an extremely large entepicondyle. The lengths between proximal and distal articular surfaces of the radius and ulna measured only 50 percent the length of the humerus. The manus is wide, with a massive radiale and a hook-shaped pisiform; both of these bones appear to have acted to increase the mechanical efficiency of elements of the antebrachial musculature. The pelvic girdle is also stoutly built, but the acetabulum does not appear to have limited femoral movement. The femur has a sharp, well-defined adductor ridge. The tibia and fibula are approximately equal in length to elements of the antebrachium. Indications of a system of cruciate ligaments are present in well preserved femora and tibiae. The pes is widely splayed. No mesotarsal joint is evident. Reconstruction of the hind limb musculature is indicative of a powerful propulsive musculature, including a well developed M. caudifemoralis that most likely acted as a primary femoral retractor. Despite the apparently short humeral and femoral excursion arcs, Labidosaurus demonstrates a variety of adaptations that functioned to increase stride length. Although it does not appear to have been fast-moving, Labidosaurus was clearly a terrestrial reptile.

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