Biostratigraphic subdivisions of the Middle Devonian, the Early Eifelian Strizhkovo Beds and newly recognized Late Eifelian Bobkovo Beds, are dated according to tabulates and rugose corals and brachiopods in the northwestern Rudny Altai. The Strizhkovo Beds are correlated with the Ahrdorf and Junkerberg Beds, while the Bobkovo Beds are correlated with the Freilinger and Ahbach Beds of the Eifelian type locality. The Bobkovo complex of brachiopods is similar in composition to the complexes of the Padaukpin limestones of Burma, Pesterevka Beds of the Salair, zone of Spinospirifer diluvianoides - Radiomena irregularis (Volchevorotskaya Formation) of Caucasus, Skala Beds of Poland, Greifenstein limestone of Germany, and to the brachiopod complex from the middle part of the Portilla Formation in Spain. Comparison of the complexes shows migration ways of the Eifelian brachiopods with predominant flows of the Prototethys paleoocean in the Eifelian.
