The paper presents a new understanding of the geologic composition and geodynamic evolution of the Mongol-Okhotsk Fold Belt. It considers the issues related to recognition and substantiation of the Amur composite microcontinent (Amuria superterrane). We analyze the latest data on the geologic composition, age, and paleomagnetism of the Neoproterozoic-Paleozoic complexes, such as the Argun terrane and neighboring structures of Transbaikalia and Mongolia, as one of the key elements of Amuria. In particular, we have refined the age of a number of Precambrian and Paleozoic stratified and magmatic stages and demonstrated the absence of an Archean-Paleoproterozoic crystalline basement. Using a set of our own paleomagnetic and paleontological data, we have substantiated the equatorial position of the Argun terrane in the close proximity to Siberia at 560-525 Ma. The results of our study and the performed analysis of available geological data on the Argun terrane and neighboring Transbaikalia and Southeastern Asia territories point to the fallacy of previous arguments about the Amur composite microcontinent as a single tectonic unit, whose collision led to the formation of the folded structures of the Mongol-Okhotsk belt. This conclusion is of crucial importance for reconstructing the geodynamic evolution of the eastern part of the Central Asian Fold Belt in the Neoproterozoic, Paleozoic, and Mesozoic.