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在兰州盆地渐新统韩家井组新发现的巨犀化石,属于南坡坪动物群,该动物群主要由大小两类动物组成.小型哺乳动物主要为梳趾鼠Ctenodactylidae等草原啮齿类,大型林栖哺乳动物主要由巨犀Paraceratherium、副狶Paraentelodon等组成.动物群23个属种类型中,森林型占~40%,草原型占~60%.与同期南北两侧的临夏椒子沟动物群和党河叮当沟动物群相比较,明显具有过渡区特点.以哺乳动物化石证据推测,渐新世中国干旱带南界很可能从兰州盆地附近通过.
The newly discovered giant rhinoceros fossils in the Hanjijing Formation of the Oligocene Hanjiajing Formation in the Lanzhou Basin belong to the Nanpoping fauna, which mainly consists of two types of animals: small mammals mainly grassland rodents such as Ctenodactylidae and large forest habitats The mammals are mainly composed of Paraceratherium, Paraentelodon, etc. Among the 23 genera of the fauna, the forest type accounts for 40% and the grassland type accounts for ~ 60% Compared with the Dangdang dangdang fauna in the Dangtang River, it is obvious that there is a transitional zone, and based on mammalian fossil evidence, it is probable that the southern boundary of the Oligocene Chinese arid zone is likely to pass near the Lanzhou basin.