Rare and Endemic Elements in Triassic Tetrapod Assemblages of Obshchii Syrt Highland (Eastern Europe)
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and Endemic Elements in Triassic Tetrapod Assemblages of Obshchii Syrt Highland (Eastern Europe) I. V. Novikova, b, *, A. G. Sennikova, b, **, and A. V. Ivanovc, *** a
Borissiak Paleontological Institute, Russian Academy of Sciences, Moscow, 117647 Russia b Kazan Federal University, Kazan, 420008 Russia c Gagarin State Technical University, Saratov, 410054 Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected] Received December 24, 2019; revised January 21, 2020; accepted January 21, 2020
Abstract—The historical sequence of Early Triassic tetrapod communities in the Obshchii Syrt area includes eight consecutive faunal assemblages: this degree of detail in the identification of evolutionary stages is unique on a global scale. Temnospondyl amphibians are the dominant elements in these tetrapod assemblages, with three capitosauromorph groups (capitosaurids, benthosuchids, and trematosaurids) characterized by the widest distribution. Reptile remains are much less frequent. The paper provides a brief overview of the findings of rare and endemic tetrapod groups known from the Lower Triassic of Obshchii Syrt. These include amphibians (qantasids, lonchorhynchids, selenocarine capitosaurids, rhytidosteids, plagiosaurs, some forms of benthosuchids and trematosaurids, and chroniosuchians, the relict anthracosaurs) and reptiles (eosauropterygians, theriodonts, individual procolophonid, protorosaurian, and thecodontian genera). The peculiarity of the systematic composition of the Early Triassic tetrapod communities of Obshchii Syrt and Southern CisUrals with respect to that of the coeval fauna of terrestrial vertebrates of the more northern regions of Eastern Europe is emphasized, as is the legitimacy of considering these two areas as a specific region characterized by the distinctive character of their zoogeographical connections. Keywords: Eastern Europe, Obshchii Syrt Highland, Early Triassic, tetrapod assemblages DOI: 10.1134/S0031030120050111
The Triassic deposits of the Obshchii Syrt Highland are exclusively continental facies, assigned to the Lower Triassic, and well characterized with regard to the remains of land vertebrates, which play a leading role in partitioning and correlation. The historical sequence of the Early Triassic tetrapod communities revealed for this territory includes eight successive faunal assemblages: this degree of detail in the identification of evolutionary stages is unique on the global scale. The largest stages (faunas) are named according to the dominant genera of temnospondyl amphibians: these are (in ascending order): Tupilakosaurus (Lower Induan, Vokhmian horizon), Selenocara–Syrtosuchus (Upper Induan, Zaplavnian horizon), Benthosuchus (Lower Olenekian, Rybinskian horizon), Wetlugasaurus (Lower Olenekian, Sludkian and Ust’mylian horizons) and Parotosuchus (Upper Olenekian, Fedorovkian and Gamian horizons), with two associations identified within each of the last three faunas (Novikov, 2018). Temnospondyl amphibians are the dominant elements in these tetr
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