Ustmylian Gorizont

The Ustmylian Gorizont ("Ustmylian Horizon") is a Lower Triassic biostratigraphic unit in Western Russia. The Ustmylian Gorizont is the youngest subunit of the Vetlugian Supergorizont, lying above the Sludkian Gorizont and below the Yarenskian Gorizont. It corresponds to the later part of the early Olenekian stage. Along with the Sludkian Gorizont, the Ustmylian Gorizont is encompassed by the "Wetlugasaurus fauna", named after a capitosaur amphibian index fossil. While the Sludkian is characterized by Wetlugasaurus angustifrons, the Ustmylian is characterized by Wetlugasaurus malachovi.^[1]^[2]

The Ustmylian is exposed in several svitas (equivalent to geological formations) spread out over a wide area. These include the upper part of the Charkabozhskaya Svita (Charkabozh Formation) in the Pechora Basin, the Bereznikovskaya Svita in the Moscow Syncline, the Pizhmomezen'skaya Svita near the Mezen River, and the Gostevskaya Svita near the Samara River. Differentiating the Sludkian and Ustmylian can be difficult elsewhere.^[1]^[3]^[2]

References

^ ^a ^b Shishkin, M.A.; Ochev, V.G.; Lozovskii, V.R.; Novikov, I.V. (2000). "Tetrapod biostratigraphy of the Triassic of Eastern Europe". In Benton, M.J.; Shishkin, M.A.; Unwin, D.M.; Kurochkin, E.N. (eds.). The Age of Dinosaurs in Russia and Mongolia. Cambridge: Cambridge University Press. pp. 140–159. ISBN 9780521545822.
^ ^a ^b Shishkin, M.A.; Sennikov, A.G.; Novikov, I.V.; Ilyina, N.V. (2006). "Differentiation of Tetrapod Communities and Some Aspects of Biotic Events in the Early Triassic of Eastern Europe". Paleontological Journal. 40 (1): 1–10. doi:10.1134/S0031030106010011. S2CID 129895753.
^ Tverdokhlebov, Valentin P.; Tverdokhlebova, Galina I.; Surkov, Mikhail V.; Benton, Michael J. (2003). "Tetrapod localities from the Triassic of the SE of European Russia". Earth-Science Reviews. 60 (1): 1–66. doi:10.1016/S0012-8252(02)00076-4. ISSN 0012-8252.