Thirteen million years ago in South America, the Pebas Mega-Wetland System sheltered multi-taxon crocodylian assemblages, with the giant caiman Purussaurus as the top predator. In these Miocene swamps where reptiles and mammals coexisted, evidence of their agonistic interactions is extremely rare. Here, we report a tibia of the mylodontid sloth Pseudoprepotherium bearing 46 predation tooth marks. The combination of round and bisected, shallow pits and large punctures that collapsed extensive portions of cortical bone points to a young or sub-adult Purussaurus (approx. 4 m in total length) as the perpetrator. Other known crocodylians of the Pebas System were either too small at adulthood or had discordant feeding anatomy to be considered. The pattern of tooth marks suggests that the perpetrator attacked and captured the ground sloth from the lower hind limb, yet an attempt of dismembering cannot be ruled out. This discovery from the Peruvian Amazonia provides an unusual snapshot of the dietary preferences of Purussaurus and reveals that prior to reaching its giant size, young individuals might have fed upon terrestrial mammals of about the size of a capybara.

十三万年前的南美洲，Pebas兆湿地系统庇护多类群crocodylian组合，与巨大的凯门鳄普鲁斯鳄作为顶级捕食者。在这些爬行动物和哺乳动物共存的中新世沼泽中，它们激动相互作用的证据极为罕见。在这里，我们报告的mylodontid懒的胫骨Pseudoprepotherium轴承46捕食牙痕。圆形和一分为二的浅坑和大穿孔的组合使大量皮质骨塌陷，指向年轻或亚成年的Purussaurus（全长约 4 m）作为肇事者。其他已知的 Pebas 系统鳄鱼要么在成年时太小，要么有不协调的进食解剖结构，无法考虑。牙齿痕迹的图案表明肇事者从下后肢攻击并捕获了地懒，但不能排除肢解的企图。秘鲁亚马逊河的这一发现提供了普鲁斯龙饮食偏好的不同寻常的快照，并揭示了在达到其巨大体型之前，年轻个体可能以水豚大小的陆生哺乳动物为食。