Abstract: As a classic vertebrate fossil locality of the American Museum of Natural History Central Asiatic Expeditions in the 1920s and 1930s, the Tunggur Tableland in central Nei Mongol (Inner Mongolia) has played an important role in late Cenozoic terrestrial mammalian palaeontology and biochronology of Asia. Field work since the mid-1990s has greatly expanded the faunal representations to include mammal assemblages (particularly those of small mammals) from Early Miocene to Pliocene (Qiu et al., 2006). The mammalian faunal sequence that has been established in Nei Mongol has the potential to become a standard of comparison for East Asia. Faunal changes in the Tunggur area are also important for gaining an in-depth view of regional differentiations in palaeoenvironment and zoogeography. In August 2005, field studies were done at two localities on the Tunggur Tableland with the objectives of locating and identifying middle to late Cenozoic vertebrate fossils and dating them on the basis of the palaeomagnetic polarity time scale. The thickest section sampled is at Aoerban (43°20’21.6”N, 113º54’48.6”E) where nearly 50 m of interbedded claystone, siltstone, and fine-grained sand are reversely magnetized except for about 5 m of brownish-tan claystone near the base that records normal polarity. The polarity for the Aoerban section suggests a correlation to the period near the Chron 5Dr or 6r, which is roughly in the 18–20 Ma age range. The section also was sampled for small mammal fossils, which tentatively are assigned to Early Miocene age. The second locality sampled is Aletexire (43º47’21.6”N, 113º05’25.0”E) where about 13 m of siltstone and fine sandstone that contain probable Tairum Nor fauna (Wang et al., 2003) record normal polarity.