Abstract:  Lower incisor fossils of Aprotodon lanzhouensis collected from the Early Miocene deposits in the Linxia Basin, are described in this paper. Characteristically, they are relatively robust and strongly curved. The discovery of the new specimens causes the occurrence of Aprotodon across the Oligo-Miocene boundary in the Linxia Basin to be completely confirmed. The chronological and geographical distribution of Aprotodon was essentially coincident with that of giant rhinos, but the localities and numbers of individuals recording Aprotodon were relatively rare. The mandibular morphological function of Aprotodon suggests that this form lived in sparseriparian mosaics within the arid part of northwestern China, and South andCentral Asia from the Late Eocene to the Early Miocene. Aprotodonexperienced total extinction before the Middle Miocene, which possibly resulted from climatic changes. The pattern of occurrence of Aprotodon also indicates that the climatic and environmental conditions of the Linxia Basinduring the Early Miocene were similar to relatively open woodlands of the Late Oligocene, in contrast to dense forests of the Middle Miocene.

摘要： 记述了在临夏盆地早中新世地层中发现的兰州巨獠犀(Aprotodon lanzhouensis)的下门齿化石，其特点为非常粗壮并强烈弯曲。新材料的发现使巨獠犀在临夏盆地的延续时代跨越渐新世/中新世界线的推测得到完全证实。巨獠犀分布的地质时代和地理范围与巨犀重合，但巨獠犀的化石地点和个体数量都相当稀少。巨獠犀的下颌形态功能特点指示其生活于晚始新世至早中新世中国西北、南亚和中亚干旱环境地带中镶嵌分布的少量近水环境。巨獠犀在中中新世之前彻底绝灭，其原因可能是气候变化的结果，也说明临夏盆地早中新世的环境特征与晚渐新世的疏林系统相似，而不同于中中新世的茂密森林。