Taxonomic reassessment of large mammals from the Pleistocene Homo-bearing site of Tham Wiman Nakin (Northeast Thailand): relevance for faunal patterns in mainland Southeast Asia

Abstract

Tham Wiman Nakin or “Snake Cave” has so far been recognized as being the only late Middle Pleistocene Homo-bearing fauna, dated to older than 169 ka, in mainland Southeast Asia. Since the last two decades, the highly diversified mammal fauna found from this cave has been widely used as standard references for several studies, though the majority of fossil primates, carnivores, and ungulates have never been described in detail. This paper presents taxonomic descriptions of unpublished fossil specimens from the long-known collection of Tham Wiman Nakin. As a result, the fauna of Tham Wiman Nakin consisted of at least 28 large mammal taxa. Although several previously described specimens are re-assigned to different tooth elements and/or mammal taxa, our taxonomic study confirms the existence of most of the species identified from the previous work and describes three additional taxa for the locality: an Asian badger, a tiger, and a Himalayan goral. The Tham Wiman Nakin fauna is one of the most diverse Pleistocene mammals, including a hominin, in mainland Southeast Asia and documents long-term survivors of living species since the late Middle Pleistocene. Based on several recent dates of fossil sites in mainland Southeast Asia, biochronological data imply a possible faunal age up to the maximum of 300 ka for the Tham Wiman Nakin fauna, but younger than that of Pha Bong where Gigantopithecus was present. Fossil records in the region also suggest a relatively stable fauna through Pleistocene glacial-interglacial cycles, at least from the late Middle to latest Pleistocene. The extinction occurring in the mainland varied across taxa and likely resulted in less impacted biodiversity loss prior to the Holocene, compared to other continents, as indicated by the small proportion of species becoming extinct during each interval. The importance of stable mosaic habitats through time may provide clues to the long-term survival of several large mammal taxa in the region.