New subfossil bones of a Réunion Giant Tortoise, Cylindraspis indica (Schneider, 1783), from a lava tunnel under a mid-elevation windward rainforest on Réunion Island

Abstract

We report the discovery of subfossil remains of a juvenile Réunion Giant Tortoise, Cylindraspis indica, in a lava tunnel beneath remnant mid-elevation native tropical rainforest on Réunion Island. Located at an elevation of 726 m in the Plaine des Grègues managed forest, this find is the highest fossil record of the species on the island. For the first time, these remains provide paleontological confirmation of historical accounts from the 17^th–18^th century reporting tortoises in upland areas. These specimens also highlight the potential of submontane and montane lava tubes as paleontological archives. Radiocarbon dating yielded an age of 665 ± 30 BP with 95.4% probability, corresponding to AD 1296–1399 and indicating that the specimen predates permanent human settlement (ca. 1665) by approximately three centuries. Although palynological analyses were unsuccessful, flora inventories revealed a diverse assemblage of native fleshy-fruited trees, suggesting that C. indica may have played a crucial role as megafaunal seed disperser. Beyond its paleontological significance, this discovery thus lends legitimacy to rewilding experiments involving functional analogues of extinct tortoises.