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

ABSTRACT

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 C₄ 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.

KEYWORDS:

• Spotted hyaena
• stable carbon isotope
• palaeoecology
• Tham Phedan
• Sundaic subregion
• Quaternary

Acknowledgments

We thank geologists and technicians from the Department of Mineral Resources (DMR) who participated in fieldwork activities: Mana Rugbumrung, Cherdchan Pothichaiya, Thapanee Pengtha, Russarint Siripattarapureenon, Nattanakorn Songpracha, Prasopsook Sritangwong and Jirasak Charoenmit. We also thank Satapat Kumpitak (Chulalongkorn University) and Manatthawut Chusaeng (Krabi Caving Club) for their fieldwork assistance as well as Peter Tung (University of Tübingen) for stable isotope analytical techniques and works with the mass spectrometer. Our grateful thanks are expressed to the Krung Yan Subdistrict Administrative Organization (Thung Yai District, Nakhon Si Thammarat) for allowing us to excavate fossils at the site. We would like to express our gratitude to Hugues-Alexandre Blain and two anonymous reviewers whose comments and suggestions helped improve and clarify this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/08912963.2023.2283936

Additional information

Funding

This work was supported by the Fundamental Fund (FF) 2022 (Thailand Science Research and Innovation Fund, Chulalongkorn University) [CU_FRB65_dis (13)_101_23_31]. The costs of stable isotope analyses were partially funded by the Georg Forster Research fellowship (Alexander von Humboldt Foundation, Germany) to K.S. (between 2018 and 2020).