The hind limb skeleton and cursorial adaptations of the Plio-Pleistocene rabbit Hypolagus beremendensis

Hypolagus beremendensis, a representative of the Archaeolaginae, was one of the most abundant and widespread leporids in the Plio−Pleistocene of Europe. The vast accumulations of skeletal remains from the Polish Pliocene sites (Węże 1, Rębielice Królewskie 1 and 2, and Kadzielnia 1) yielded thousands of bones representing almost all skeletal regions. The detailed hind limb morphology of Hypolagus beremendensisis presented in comparison with five extant leporids (Lepus europaeus, Oryctolagus cuniculus, Pentalagus furnessi, Sylvilagus floridanus, and S. brasiliensis), which represent a wide range of locomotor adaptations. The UPGMA analysis of 98 metric characters places Hypolagus beremendensis next to the leporine rabbits. Hypolagus beremendensis has the os coxae, femur, and talus most similar to P. furnessi, tibia and calcaneus to the leporine rabbits, and the structure of foot to Lepus. The elongation of the foot and tibiofibular segment in relation to the femur indicates an advanced cursorial adaptation and a relatively steep jump. The similarities in the proximal segments (os coxae and femur) between Hypolagus and Pentalagus highlight the conservative morphology of this region in the Leporidae.