The Bashkirian stratotype is subdivided into nine biozones of fusulinids. This is the most accurate classification to date. Descriptions of the main taxa are provided. The more representative algae or pseudo-algae are Donezella lutugini, Cuneiphycus texana and Ungdarella uralica. The fusulinids markers are successively: Plectostaffella bogdanovkensis, Plectostaffella jakhensis, Semistaffella variabilis, Pseudostaffella aff, compressa, P. antiqua, P. proozawai, P. praegorskyi, Staffellaeformes staffellaeformis, Ozawainella pararhomboidalis, Profusulinella pararhomboides, Aijutovella tikhonovichi. At the top of the shallow marine Serpukhovian platform, the depositional environments evolve from inner to outer ramp. They are symptomatic of a gradual flooding of the Russian platform margin at the front of the incipient Pre-uralian foredeep trough. The Bashkirian stratotype comprises two major sequence boundaries that correspond to two periods of faunal diversification : the first, in the Akavassky horizon, is an emersion and, the second, without emersion, is at the upper part of the Tashastinsky horizon. The first could be compared to the unconformities located al the transition between Namurian and Westphalian stages in Europe and Morrowan-Atokan in North America. its formation is contemporaneous with the minimum oi temperature observed in the South Uralian and North Caucasian regions and attests the eastward migration of the Gondwanan glaciation during the Upper Paleozoic and the collision between Gondwana and Laurussia.