The Pleistocene grassland-dominated mammal fauna from Tham Kra Duk (Nakhon Si Thammarat, Peninsular Thailand)

Controversy exists as to whether the Pleistocene vegetation in northern Sundaland was dominated by lowland tropical grasslands or rainforests, due to limited palaeoecological evidence recorded from the region. We describe a new Pleistocene large mammal fauna from Tham Kra Duk, a cave in the Tham Phedan mountain, Nakhon Si Thammarat Province in Peninsular Thailand, with emphasis on its palaeoecological and palaeoenvironmental investigations using the stable isotope analysis of mammalian tooth enamel. The fossil site has yielded at least nine mammalian taxa almost comparable to late middle to latest Pleistocene faunas in the mainland, thus suggesting the same biogeographic mammal elements with a range extension south of the Kra Isthmus. The stable isotope results indicate that mixed woodland to grassland ecosystems were dominated by C-4 vegetation in the area. This supports the assumption that the expansion of Pleistocene tropical savanna ecosystems might have held the key to facilitating the southward distribution range of grazing mammals such as gaurs and Himalayan gorals into the Thai-Malay Peninsula. The presence of the Tham Kra Duk fauna was probably linked to some major biogeographic events of Pleistocene hominin and mammal migration through the land-bridge peninsula into the islands of Southeast Asia during a period of glaciation.

Automated summary

This study describes a Pleistocene mammal fauna discovered in a cave in Peninsular Thailand and investigates its paleoecological and paleoenvironmental characteristics using stable isotope analysis. The results suggest that the area was dominated by mixed woodland to grassland ecosystems with C-4 vegetation, supporting the hypothesis that the expansion of Pleistocene tropical savanna ecosystems facilitated the southward distribution of grazing mammals into the Thai-Malay Peninsula. The presence of this fauna may be linked to major biogeographic events during the Pleistocene glaciation period.