An assemblage of Stegodon orientalis fossils from the Yumidong Cave site in Wushan, Chongqing, with emphasis on the taphonomic analysis

Stegodont fossils have been recovered from many paleoanthropological sites in South China and Southeast Asia, marking them as one of the most important constituents in Pleistocene mammalian faunas of Asia. Yet very limited taphonomic research has been conducted so far concerning the context of their present in paleoanthropological sites. Recently, a large number of stegodont fossils have been found at the Yumidong Cave site in Wushan County, Chongqing Municipality, providing us with opportunities not only for morphological observation, but also taphonomic analysis. The studied materials include 94 cranial remains (jaws and teeth) and 54 remains of the postcrania from both the upper and lower cultural layers at Yumidong, which make up about 18.5% of the total identified specimens. Morphologically, the ridge-crest formulae, the number of mammillae and the measurements of most these specimens conform to Stegodon orientalis . Taphonomically, traces of natural activities, such as water transportation and bite marks of animals, are very few on the surface of these Stegodon remains; meanwhile, these fossils are unearthed associated with paleolithic tools in the Yumidong Cave site, among which at least three bone tools are made of incisors of Stegodon orientalis . These observations indicate that ancient human activity was the dominant cause in the accumulation of this Stegodon fossil assemblage. Due to the peculiarity of tooth replacement and attrition of these proboscideans, we are able to attribute most of each individual specimen, except two fragments of M2/3, as belonging to a distinct individual animal. The analysis of mortality age profiles shows that neonate and juvenile individuals account for more than 85% among the Stegodon fossils, indicating a type of selective mortality of immature individuals. In the schematic typology of living and extinct proboscidean age profiles, the type B of Haynes is dominated by the youngest age group which may result from hunting either by carnivores or humans. The skeletal element profiles show that the cranial and foot elements are the most numerous category. This phenomenon is always considered as a resultant taphonomic effect of scavenger behavior. But given the unique anatomic structure of proboscidean, hunting behavior cannot be ruled out here; in other words, the ancient human might hunt immature stegodonts but take a strategy of transporting the cranial and foot parts of carcass to their base camp, for these parts of stegodont contain more fat than other animals and are easy to carry. Irrespective of scavenging or hunting, the ancient humans which occupied the Yumidong Cave site appear to have preferred neonate and juvenile stegodonts rather than the adults, which were not easy to hunt. Alternatively, meat from neonate and juvenile Stegodon may have had better taste and nutritional value. Perhaps, a combination of these two factors may have motivated the highly selective exploitation of juvenile Stegodon by early humans at the Yumidong site.