Semantor macrurus Orlov, 1931 (Carnivora, Mustelidae): Morphology of the Hind Limb and a New View on Its Paleobiology

Abstract

Based on the analysis of joints morphology in the hind limb of Semantor macrurus, it is established that the amplitude of flexion–extension mobility in the hip, knee (stifle), and talocrural (ankle) joints could have reached 90°; the adduction–abduction mobility in the hip joint was up to 60° and, in the talocrural joint, up to 65°. The talocrural joint is hinged and multiaxial, providing a wide range of movements of the autopodium in the course of aquatic locomotion. The hind limb is of the free type. The exterior of Semantor resembles that of otter. The increased length of the crus suggests that the limb was adapted for stroke function (rowing).