Re-examination of the fossil raccoon dog (Nyctereutes procyonoides) from the Penghu channel, Taiwan, and an age estimation of the Penghu fauna

Abstract

The Penghu channel, along the western shore of Taiwan, is well known for yielding numerous Middle to Late Pleistocene mammalian fossils, including an archaic human mandible. In this work, we examine a fossil mandible of the raccoon dog, Nyctereutes procyonoides, which was recovered from the bed of the Penghu channel, and compare this with extant raccoon dog subspecies in East Asia. Two-dimensional geometric morphometric analysis of the lower first molar of the Penghu specimen demonstrates that continental and Japanese populations were clearly separated. This indicates that amongst continental populations, the Penghu specimen has a shape intermediate between extant Chinese and Korean populations. Results indicate that the Penghu raccoon dog is phylogenetically closer to the extant continental raccoon dog, rather than those of Japan, and that the Chinese and Korean populations were not greatly separated at that time. When considering the fact that recent phylogenetic and population genetic studies report that the Korean raccoon dog population separated from other continental populations at the last glacial maximum, we can state that the Penghu fauna is at least 20000 years old.