Abstract: The Oligocene sedimentary sequence of the Taatsiin Gol and Taatsiin Tsagaan Nuur area is of unique stratigraphic importance: here, the exposed sediments of the Hsanda Gol and the Loh Formations display multiple fossil horizons and interbedded basalt layers. In the frame of a Mongolian–Austrian project, 289 fossil taxa (11 Gastropoda, 2 Amphibia, 9 Reptilia and 267 Mammalia) were collected from 85 fossil horizons of 33 sections/fossil sites of the study area. The taxa were identified by an international team of specialists. This contribution presents comprehensive mammal lists of all localities. By integrating the new data on large and small mammals, the Mongolian informal biozones A, B, C, C1 were updated. 40Ar/39Ar-datings provide at least two groups of basalt ages, the Early Oligocene basalt I group around 31.5 Ma and the Late Oligocene basalt II group around 28 Ma. They serve as chronological tie points in the Oligocene mammalian stratigraphy. From the Early to the Late Oligocene the mammal associations underwent remarkable changes involving a significant decrease of species numbers in the Late Oligocene. This trend was most striking in creodont, carnivore and ruminant communities.

摘要： Taatsiin Gol和Taatsiin Tsagaan Nuur地区的渐新世沉积序列具有重要的地层学意义：这里出露的三达河组和Loh组沉积含有多个含化石层和玄武岩夹层。在蒙古−奥地利合作项目中，从研究区域的33个剖面/化石地点的85个含化石层中采集了289种化石(11种腹足类，2种两栖类，9种爬行类和267种哺乳类)。本文提供了所有地点的完整的哺乳动物清单，并结合大、小哺乳动物的新资料，对蒙古非正式的生物带A, B, C和C1进行了更新。40Ar/39Ar测年给出了至少两组玄武岩年龄：早渐新世玄武岩I组大约31.5 Ma, 晚渐新世玄武岩II大约28 Ma。它们可以用作渐新世哺乳动物地层学的年代校正点。从早渐新世至晚渐新世，哺乳动物群发生了显著的变化，包括晚渐新世种数的明显减少。这种趋势在肉齿类、食肉类和反刍类中最为突出。