A mammalian fossil from the Dingqing Formation in the Lunpola Basin,northern Tibet,and its relevance to age and paleo-altimetry  

作　　者：DENG Tao WANG ShiQi XIE GuangPu LI Qiang HOU SuKuan SUN BoYang 

机构地区：[1]Key Laboratory of Evolutionary Systematics of Vertebrates,Institute of Vertebrate Paleontology and Paleoanthropology,Chinese Academy of Sciences,Beijing 100044,China [2]Gansu Provincial Museum,Lanzhou 730050,China [3]Graduate University of the Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Chinese Science Bulletin》2012年第2期261-269,共9页

基　　金：supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-Q09);the National Basic Research Program of China (2012CB821906);the National Natural Science Foundation of China (40730210)

摘　　要：The distal extremity of a rhinocerotid humerus from the upper part of the Dingqing Formation at the Lunbori locality in Baingoin County,northern Tibet,is the first mammalian fossil found in Cenozoic deposits of the Lunpola Basin.The medial condyle of the distal trochlea of the humerus specimen from Lunbori gradually contracts from medially to laterally.The margin of the medial surface of the medial condyle is not prominent,the well-developed medial epicondyle strongly extends posteriorly,and is divided from the articular facet of the medial condyle by a groove;all of which are characteristic for the Rhinocerotidae.The medial condyle is wide at the bottom and narrow at the top.The medial collateral ligament fossa is relatively shallow,and the medial collateral ligament tubercle is very weak.The medial part of the upper margin of the medial condyle smoothly connects to the bony surface above,but there is no clear boundary between them.All of these characteristics are identical with those of Plesiaceratherium.These comparisons imply that the Lunbori specimen is closest to Plesiaceratherium gracile in the Shanwang Fauna from Linqu,Shandong Province,in size and morphology.Thus,its age is suggested to be the late Early Miocene(Shanwangian Age),about 18-16 Ma.Discovery of the rhinocerotid fossil suggests that the upper part of the Dingqing Formation deposited in the Neogene.While adjusting to paleo-temperatures of the Early Miocene,a paleo-ecosystem reconstruction indicates that the paleo-elevation was close to 3000 m in the Lunpola Basin during this time.The distal extremity of a rhinocerotid humerus from the upper part of the Dingqing Formation at the Lunbori locality in Baingoin County, northern Tibet, is the first mammalian fossil found in Cenozoic deposits of the Lunpola Basin. The medial condyle of the distal trochlea of the humerus specimen from Lunbori gradually contracts from medially to laterally. The margin of the medial surface of the medial condyle is not prominent, the well-developed medial epicondyle strongly extends posteriorly, and is divided from the articular facet of the medial condyle by a groove; all of which are characteristic for the Rhinocerofidae. The medial con- dyle is wide at the bottom and narrow at the top. The medial collateral ligament fossa is relatively shallow, and the medial collat- eral ligament tubercle is very weak. The medial part of the upper margin of the medial condyle smoothly connects to the bony surface above, but there is no clear boundary between them. All of these characteristics are identical with those of Plesiacera- therium. These comparisons imply that the Lunbori specimen is closest to Plesiaceratherium gracile in the Shanwang Fauna from Linqu, Shandong Province, in size and morphology. Thus, its age is suggested to be the late Early Miocene （Shanwangian Age）, about 18-16 Ma. Discovery of the rhinocerotid fossil suggests that the upper part of the Dingqing Formation deposited in the Neogene. While adjusting to paleo-temperatures of the Early Miocene, a paleo-ecosystem reconstruction indicates that the paleo- elevation was close to 3000 m in the Lunpola Basin during this time.

关 键 词：哺乳动物化石 伦坡拉盆地 西藏北部 年龄 晚中新世 晚第三纪 生态重建 新生代 

分 类 号：P618.130.2[天文地球—矿床学] Q915.87[天文地球—地质学]