Geologicheskii Vestnik

The article discusses the history of the study of the Sterlitamak Shikhans, the Early Permian non-ammonoid cephalopods originating from there and presents the results of recent studies. Two clearly distinguishable complexes are characterized: the Asselian-Sakmarian boundary complex and the Late Artinskian complex. The cephalopods of the first complex were associated with reef environments that existed in the area at the very beginning of the Permian. The taxonomic composition of the AsselianSakmarian complex is characterized by a predominance of convoluted forms, which distinguishes it from the same age communities of the Southern Urals, not associated with reef facies. The Artinskian community replaced the Asselian-Sakmarian community during the post-reef phase of basin development, due to the closure of the Ural corridor and a flattening of conditions along its entire length. Nectobenthic Orthoceratoidea constitutes a significant part of the Late Artinskian complex. The increase in the content of nectobenthic forms indicates a change in the ecological structure of this community in line with more pelagic conditions. The main collection of cephalopods was collected from the quarry at the site of the former Shikhan Shakhtau and included 35 genera and 46 species. So far, nine genera and species have been described from the Asselian-Sakmarian interval of Toratau, Kushtau, Yuraktau, and Malyi Shikhan, and 10 genera and 11 species from the Artinskian interval. In 2022, members of the Laboratory of Mollusks of Palaeontological Institute of the Russian academy of sciences conducted fieldwork on the slopes of the Shikhans. The collection of cephalopod mollusk shells was formed. Species Domatoceras sp., Megaglossoceras barskovi Leonova et Shchedukhin, 2020 and Shatoceras umbilica‑ tum Leonova et Shchedukhin, 2020 were identified from Asselian-Sakmarian deposits in Toratau, and Liroceras shakhtauense Leonova et Shchedukhin, 2020 and Uralorthoceras tzwetaevae Shimansky, 1951 were identified from the same age rocks in Yuraktau. The study of the new materials allows us to expand our understanding of the taxonomic diversity of the Sterlitamak Shikhans.

Nautiloidea, Orthoceratoidea, Bactritoidea, Early Permian, Asselian, Sakmarian, Artinskian, Sterlitamakian shikhans

• Gorozhanin V.M., Gorozhanina E.N. (2022). Genezis neptunicheskih daek v sterlitamakskih shihanah. [The genesis of neptunic dikes in the Sterlitamak Shikhans] Geologicheskij vestnik, (2), 69–80 (in Russian).
• Korolyuk I.K. (1985). Metody i rezul’taty izucheniya permskogo rifogennogo massiva Shahtau [Methods and results of the study of the Permian riffogenic massif Shakhtau]. Nauka Press, Moscow, 111 p. (in Russian).
• Kruglov M.V. (1928). Verhnekamennougol’nye i permskie nautilidy Urala [Upper Carboniferous and Permian nautilids of the Urals]. Trudy Geol. muzeya AN SSSR, (3), 63–206 (in Russian).
• Nalivkin D.V. (1932). Uchenie o fatsiyakh [The doctrine of facies]. Gos. nauchno-techn. gorno-geol. izdatel’stvo, Moscow-Leningrad, 208 p. (in Russian).
• Rauzer-Chernousova, D.M., Ivanova, Ye.A., Korolyuk, I.K., Morozova I.P., Fotiyeva, N.N. (1977). On the characterization of the stratotype of the Sterlitamakian horizon (Lower Permian, Shakhtau Massif, Bashkiria). Bull. Mosk. Obshch. Ispyt. Prir., Otd. Geol., 52 (6), 24–37. (in Russian).
• Ruzhencev V.E. (1951). Nizhnepermskie ammonity Yuzhnogo Urala. 1. Ammonity Sakmarskogo yarusa [Lower Permian ammonites of the South Urals. 1. Ammonites of the Sakmarian stage]. USSR Academy of sciences Press, Moscow, 188 p. (Trudy Paleontologicheskogo Instituta Akademii Nauk SSSR, V. 33) (in Russian).
• Ruzhencev V.E., Shimanskiy V.N. (1954). Nizhnepermskie svernutye i sognutye nautiloidei Yuzhnogo Urala [Lower Permian coiled and bent nautiloidea of the Southern Urals]. USSR Academy of sciences Press, Moscow, 150 p. (Trudy Paleontologicheskogo Instituta Akademii Nauk SSSR, V. 50) (in Russian).
• Chuvashov B.I., Prust Zh-N., Buasso T., Vennan E., Chernyh V.V. (1996). K istorii formirovaniya Sterlitamakskih shihanov (rannepermskie rifovye massivy Yuzhnogo Predural’ya [On the history of the formation of the Sterlitamak Shikhans (Early Permian reef massifs of the Southern Urals)]. Ezhegodnik 1995. Ekaterinburg: Inst. Geol. i geoh. UrO RAN, 25–34 (in Russian).
• Shimanskiy V.N. (1954). Pryamye nautiloidei i bak‑ tritoidei sakmarskogo i artinskogo yarusov yuzhnogo Urala [Orthoconic Nautiloidea and Bactritoidea of the Sakmarian and Artinian stages of the southern Urals]. Nauka Press, Moscow 156 p. (Trudy Paleontologicheskogo Instituta Akademii Nauk SSSR. V. 44) (in Russian).
• Murchison R., Verneuil E., Keyserling A. (1845). Geology de la Russie d’Europe et des montagnes de l’Oural. Vol. II. Paléontologie. Londres, Paris, 512 p.
• Wangenheim von Qualen F.F. (1842). Übersicht geolo‑ gischer. Verchäitnissen des Gouvernements Orenburg. Verh. der R.‑K. Mineralog. Gesellsch., Jahrb. 41 p.