Based on the information of the Qinghezhen fauna, small shelly fossils of the Meishucun Stage were first discorered in the Lower Ayadeng Formation of the Bayan Obo Group, in Wu-daowan village, Shangdu, Inner Mongolia, which contain 8 gen. 8 sp. (including 1 cf. , 2 undefined sp. ), such as Hyolitha, Hyolithellus, Conodonomorpha, Siphogonuchitiida, Camenida and more than 2000 pieces of sponge spicule fossils. Thus, the age of the Bayan Obo Group is determined to be Sinian-Cambrian (to Ordovician). The discovery of small shelly fossils proves the existence of the Qinghezhen fossil group once again and testfies that the HF acid method is effective to extract fossils from low-grade metamorphic carbonate rocks.