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Buchwitz, M., Witzmann, F., Voigt, S. and Golubev, V. 2012. Osteoderm microstructure indicates the presence of a crocodylian-like trunk bracing system in a group of armoured basal tetrapods. -Acta Zoologica (Stockholm) 93: 260-280.The microstructure of dorsal osteoderms referred to the chroniosuchid taxa Chroniosuchus, Chroniosaurus, Madygenerpeton and cf. Uralerpeton is compared to existing data on the bystrowianid chroniosuchian Bystrowiella and further tetrapods. Chroniosuchid osteoderms are marked by thin internal and relatively thick external cortices that consist of lowly vascularised parallel-fibred bone. They are structured by growth marks and, in case of Madygenerpeton, by lines of arrested growth. The cancellous middle region is marked by a high degree of remodelling and a primary bone matrix of parallel-fibred bone that may include domains of interwoven structural fibres. Whereas the convergence of Bystrowiella and chroniosuchid osteoderms is not confirmed by our observations, the internal cortex of the latter displays a significant peculiarity: It contains distinct bundles of shallowly dipping Sharpey's fibres with a cranio-or caudoventral orientation. We interpret this feature as indicative for the attachment of epaxial muscles which spanned several vertebral segments between the medioventral surface of the osteoderms and the transversal processes of the thoracic vertebrae. This finding endorses the hypothesis that the chroniosuchid osteoderm series was part of a crocodylian-like trunk bracing system that supported terrestrial locomotion. According to the measured range of osteoderm bone compactness, some chroniosuchian species may have had a more aquatic lifestyle than others.

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The Moscow Syneclise on the East European Platform is an important area for the study of the continental biota of late Permian to Early Triassic age in continuous sections. This study attempts a taxonomic description of the late Permian conchostracan fauna of this area. The rich, new material was collected, bed by bed, during geological and paleontological excavations of lacustrine and fluvial deposits of the Obnora Formation and Vokhma Formation of the late Permian Zhukovian Regional Stage near the towns of Vyazniki and Gorokhovets. The conchostracan fauna of the Zhukovian Regional Stage consists predominantly ofPseudestheriaand less frequently ofPalaeolimnadiopsis. In the earliest Triassic Vokhmian Regional Stage, a more diverse fauna includingEuestheria,Magniestheria,Cornia,Palaeolimnadiopsis, andRossolimnadiopsiswas already recorded. The preliminary taxonomic determination of the pseudestheriids from the Zhukovian Regional Stage is intended to serve as a prerequisite for future studies of late Permian conchostracan biostratigraphy on the regional to interregional scale.

Pareiasaurs were one of the main clades of large herbivorous tetrapods in Middle–Late Permian continental ecosystems. Despite abundant pareiasaur material, many aspects of their biology remain poorly known. This paper provides a description of ontogenetic changes in long-bone and rib microanatomy/histology of two Upper Permian pareiasaurs from Russia, Deltavjatia rossica and Scutosaurus karpinskii. Analysis of a growth series of bones of Deltavjatia and Scutosaurus revealed rapid and cyclical growth early in ontogeny (as indicated by fast-growing fibrolamellar bone with lines of arrested growth). This was followed by a change in the growth pattern (as indicated by an outer avascular layer of lamellar bone in the cortex) and a decrease in the growth rate after 50% of maximum body size was reached in Deltavjatia and 75% in Scutosaurus (larger body sizes in Scutosaurus were attained through an extended initial period of fast skeletal growth). The study confirms that the bones of all pareiasaurs are histologically and microanatomically uniform [spongious (porous) microstructure and a very thin compact cortex] and indicate a similar growth strategy (a short initial period of rapid and cyclical growth followed by a long period of slow growth). The microanatomical characteristics of pareiasaurs do not provide a clear indication of their lifestyle.