Paleoecological implications of the large mammals from a late glacial hyena den at Besaansklip (southwestern Cape, South Africa)

Southern Africa’s Cape Floristic Region (CFR) has long been a focus of research aiming to integrate relationships between Quaternary climate dynamics, terrestrial ecosystem change, and modern human origins. Pleistocene mammal assemblages play a key role in this research. However, a lack of securely dated sites, especially from the western coastal plains of the CFR, has posed a challenge for understanding faunal communities and their connection to Pleistocene climate dynamics. Here, we present the systematic paleontology and paleoecological analysis of the large mammals from Besaansklip, a well-dated late glacial hyena den (∼16,000 years ago) from the west coast of the CFR. We identified >400 mammalian specimens from Besaansklip, which we use to infer past climate and terrestrial environments. Like other Pleistocene fossil assemblages in the region, Besaansklip has a high abundance and diversity of water-dependent grazers, many of which are extinct (e.g., Equus capensis and Syncerus antiquus) or extirpated (e.g., Connochaetes gnou). Stable carbon isotope analysis of ostrich eggshells from Besaansklip suggests a lack of C4 grasses, implying a cool growing season and dominance of winter rainfall. These findings reinforce previous models suggesting that glacial phases of the Pleistocene were associated with increased moisture availability and productivity, and perhaps an expansion of grassy vegetation in the southwestern Cape.

南非开普植物区（Cape Floristic Region, CFR）长期以来都是学界聚焦的研究热点，旨在整合第四纪气候动态、陆地生态系统变迁与现代人类起源之间的关联。更新世哺乳动物组合在该研究中扮演关键角色。然而，可靠定年遗址的匮乏——尤其是开普植物区西部沿海平原的相关遗址——极大阻碍了学界对动物群群落及其与更新世气候动态之间关联的认知。本研究针对开普植物区西海岸的贝桑斯克利普（Besaansklip）遗址展开分析，该遗址是一处定年精准的晚冰期鬣狗巢穴，距今约16000年。我们在此报告对该遗址出土大型哺乳动物的系统古生物学与古生态分析结果：本次研究从贝桑斯克利普遗址中鉴定出400余件哺乳动物标本，并以此推演该区域过去的气候与陆地环境状况。与该区域其他更新世化石组合类似，贝桑斯克利普遗址出土的依赖水源的草食动物不仅数量丰富，且多样性极高，其中不少物种现已灭绝（如Equus capensis 开普马、Syncerus antiquus 古水牛）或已在本地消失（如Connochaetes gnou 黑尾牛羚）。对贝桑斯克利普遗址出土鸵鸟蛋壳的稳定碳同位素分析结果显示，当时区域内缺乏C4草本植物，这表明该区域彼时生长季气温较低，且以冬雨型气候为主。上述研究结果进一步佐证了此前的相关模型：更新世冰期阶段与区域湿度提升、生产力提高相关，西南开普地区或许还伴随草本植被的扩张。