Plio-Pleistocene giant tortoises from Tha Chang sandpits, Nakhon Ratchasima Province, Thailand

Abstract Giant tortoises have been found from the Plio-Pleistocene sediments of Tha Chang sandpits, Nakhon Ratchasima Province, Thailand. These tortoises are represented by several individuals and are described based on carapace, plastron, limb bones, and isolated plates. Three different morphotypes of epiplastral projection are recognized, pertaining to different sexes or different ontogenetic stages. Based on their large size, thick shell, single supracaudal, well-developed epiplastral projection, gulars covering anterior part of the entoplastron or in contact with the latter, and humeropectoral sulcus posterior to entoplastron, these Thai giant tortoises are assigned to the genus Megalochelys. Thai specimens show strong similarities with large tortoises from India as well as those from Flores and Timor, and are therefore very close morphologically to Melgalochelys atlas. Our study provides new evidence about polymorphism and additional information about distribution of Plio-Pleistocene fossil giant tortoises in South and Southeast Asia.