Middle Pleistocene human femoral diaphyses from Hualongdong, Anhui Province, China

Objectives: The paleontological description and comparative analysis using discrete morphology, morphometrics (linear and geometric) and cross-sectional geometry of three femoral diaphyseal sections from the Middle Pleistocene site of Hualongdong, China. Materials and Methods: The material consists of the original Hualongdong femoral fossils and available data on femoral diaphyses from Middle and Late Pleistocene archaic humans and Middle and earlier Upper Paleolithic modern humans. The methods include visual observation, diaphyseal diameters, cross-sectional parameters (transverse areas and second moments of area derived from micro-CT scans), and geometric morphometrics using semilandmark data. Results: The Hualong 11 midshaft section is similar to other Middle and Late Pleistocene archaic humans in being transversely broad and lacking a pilaster despite a prominent linea aspera. It clusters principally with archaic human femora in all measured parameters. The Hualong 15 and 16 subtrochanteric pieces are similar to many Middle Pleistocene and early modern human femora in being transversely broad. In particular, Hualong 15 exhibits a prominent lateral (gluteal) buttress, similar to many Upper Paleolithic femora but also the Lazaret and Krapina archaic ones. In addition, Hualong 15 has a small third trochanter, a common Upper Paleolithic but rare earlier feature. Discussion: The Hualong 11 femoral piece reinforces the general Middle Pleistocene pattern, especially for eastern Eurasia from which archaic human femora are rare. The subtrochanteric proportions of Hualong 15 and 16 reinforce the Early Pleistocene and (generally) Middle Pleistocene pattern of bone distributions, but their subperiosteal contours align them (along with those of the Lazaret and Krapina femora) with Upper Paleolithic ones. It is difficult to account for these proportions from the generally broad pelves of Pleistocene archaic humans.