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Permo-Triassic sections at Vyazniki and Gorokhovets provide evidence on terrestrial events at, or close to, the Permo-Triassic boundary, the time of the largest ever mass extinction. The sedimentary succession records the overrun of a muddy playa--lacustrine depositional system by major channel belts transporting sand-grade sediments. Biostratigraphy of sections at Vyazniki and Gorokhovets (Zhukov Ravine) shows that this event occurred either at the very end of the Permian or 8 m above in the sections. The timing and nature of this event, which records increased sediment flux from the Ural Mountains, is closely comparable with that from the Southern Uralian Foreland Basin. The Vyazniki and Gorokhovets sections are 800 km from the mountain front and in a separate depositional basin, which strengthens the case that increased sediment flux from the Urals at the Permo-Triassic boundary is related to devegetation of upland catchments (increasing sediment yield) and a switch toward low-frequency but high-magnitude discharge events (increasing sediment delivery). The interbedding of fluvial and aeolian deposits provides further evidence for climatic instability and extremes in the Early Triassic. Supplementary material: Detailed reports on the ostracodes and fossil fish remains from the Zhukov Ravine sections are available at http://www.geolsoc.org.uk/SUP18402. doi: 10.1144/0016-76492009-103.

Fossil fishes and tetrapods (amphibians and reptiles) have been discovered at 81 localities in the Upper Permian of the Southern Urals area of European Russia. The first sites were found in the 1940s, and subsequent surveys have revealed many more. Broad-scale stratigraphic schemes have been published, but full documentation of the rich tetrapod faunas has not been presented before. The area of richest deposits covers some 900,000 [km.sup.2] of territory between Samara on the River Volga in the NW, and Orenburg and Sakmara in the SW. A continental succession, some 3 km thick, of mudstones, siltstones, and sandstones, deposited on mudflats and in small rivers flowing off the Ural Mountain chain, span the last two stages of the Permian (Kazanian, Tatarian). The succession is divided into seven successive units of Kazanian (Kalinovskaya, Osinovskaya, and Belebey svitas, in succession) and Tatarian age, which is further subdivided into the early Tatatian Urzhumian Gorizont (Bolshekinelskaya and Amanakskaya svitas, in succession), and the late Tatarian Severodvinian (Vyazovskaya and Malokinelskaya svitas, of equivalent age) and Vyatkian gorizonts (Kulchumovskaya and Kutulukskaya svitas, of equivalent age). This succession documents major climatic changes, with increasing aridity through the Late Permian. The climate changes are manifested in changing sedimentation and the spread of dryland plants, and peak aridity was achieved right at the Penno-Triassic (PTr) boundary, coincident with global warming. Uplift of the Urals and extinction of land plants led to stripping of soils and massive run-off from the mountains; these phenomena have been identified at the PTr boundary elsewhere (South Africa, Australia) and this may be a key part of the end-Permian mass extinction. The succession of Late Permian fish and tetrapod faunas in Russia documents their richness and diversity before the mass extinction. The terminal Permian Kulchomovskaya and Kutulukskaya svitas have yielded respectively some 6 and 13 species of fishes (sharks, bony fishes, lungfishes) and 11 and 14 species of tetrapods (aquatic amphibians, herbivorous and carnivorous reptiles of all sizes up to the hippo-sized pareiasaurs and sabre-toothed gorgonopsians). Immediately following the end-Permian environmental catastrophe, earliest Triassic faunas consisted only of a few fish taxa and small, aquatic tetrapods, in low-diversity, low-abundance assemblages. Keywords: Permian; Triassic; Mass extinction; Tetrapod; Amphibian; Reptile; Russia; Urals; Stratigraphy