Eocene fossil rodent assemblages from the Erlian Basin (Inner Mongolia, China): Biochronological implications

On the basis of the comparison of the rodent assemblages, I consider that the age of upper part of the Nomogen Formation corresponds to the Bumbanian land mammal age. The Bumbanian, Arshantan, and Irdinmanhan land mammal ages are correlated respectively to the early Ypresian, the middle-late Ypresian, and the early Lutetian of the Geological Time Scale. The Bumbanian and Irdinmanhan land mammal ages are also correlated to the early Wasatchian and the early Uintan (or the later Bridgerian) of the North American Land Mammal Ages.