Biostratigraphic subdivision and correlation of Ordovician different-facies sections on the western slope of the Southern Urals are carried out based on conodonts and chitinozoans. Upper Ordovician conodonts are defined in the West Zilair zone, in the carbonate-terrigenous section near Nabiullino Village. They belong to important cosmopolitan taxa which allow distinguishing biostratigraphic units corresponding to the North Atlantic standard conodont scale. Successions of Middle and Upper Ordovician conodont and chitinozoan assemblages are identified in the terrigenous-siliceous sections of the East Zilair zone. Middle Ordovician chitinozoans are found in the Uraltau zone, in the metamorphic rocks of the Belekei Formation of the Suvanyak complex, previously assigned to the Precambrian. Most of the taxa in the conodont and chitinozoan assemblages have a good correlation potential due to their wide geographic range. A positive δ13C excursion of 3.3‰ was first recorded in the Nabiullino section (West Zilair zone), suggesting the initial phase of the HICE isotopic events in the Southern Urals. The development of shallow-water conodont biofacies at the top of the section suggests a sea level fall in the Late Ordovician.

Crinoids and brachiopods are described from the Silurian Uzyan Formation of the Zilair Zone in the southern Urals. The occurrence of the graptolites Coronograptus praedeubeli suggests a late Homerian (Wenlock) age for the strata. A new disparid crinoid, Cicerocrinus gracilis Donovan sp. nov., is the oldest known member of this genus. It has a long, flexible and homeomorphic column, and a tall bryozoan palaeontology terminology (IBr 2 ) (second primibrachial) axillary. All species of Cicerocrinus described previously have been limited to the Ludlow of the British Isles, Sweden and Estonia, and the Pridoli of Estonia. The poorly preserved brachiopod fauna is represented by small atrypid (Atrypa? sp.) and dalmanellid brachiopods (Levenea? sp.). The reported assemblage generally inhabited deep-water environments.

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For the first time, conodonts from the Middle — Upper Carboniferous and Lower Permian deposits were studied in the joint zone of the Pre — Ural’s foredeep and the West Ural megazone. Two sections were studied. The section in the siliceous — carbonate deposits is common in Belsk — Elets tectono — stratigraphic zone (West Ural’s megazone) and the clastic (olistostrome) section located in the southern part of the Karatau sallent (The Pre–Ural’s Foredeep) adjacent with the West Ural’s. Under field research 30 samples were taken in order to identify conodont fauna. Conodonts were found in 16 samples. Studed conodont complexes contain numerous cosmopolitan forms that determine the stratigraphic position of deposits as the Middle Carboniferous in the volume of Tashasty Horizon of the Bashkirian Stage — the Podolian Horizon of the Moscovian Stage. As result, a biostratigraphic sequence in the rank of beds with fauna was outlined: the beds with Declinognathodus marginodosus, Swadelina suberecta, the beds with Idiognathodus postsulcatus, Id. volgensis, the beds with Sw. dissecta and the beds with Id. podolskensis. The presence of the Bashkirian and Moscovian boundary deposits is proposed. The siliceous — carbonate (olistostrome) section contains the Middle, Upper Carboniferous, and Lower Permian olistoliths with conodonts, fusulinids and brachiopods. Conodonts and foraminifers of Early Permian age were identified in the matrix.