The complex body-trace fossils of Vendian soft-bodied biota have been found for the first time in the Central Urals during the study of the Vilukha and Sinii Kamen members of the Chernyi Kamen Formation of the Upper Vendian Sylvitsa Group (Kos’va River area, Perm Krai of Russia). These sedimentary sequences were exposed along the valley of the Shirokovskii Reservoir. Among the fossils, the chuariomorpha-like species Beltanelliformis konovalovi, previously described from the Konovalovka Member of the Chernyi Kamen Formation, was identified. However, the morphological analysis of the new fossil material revealed a number of principal differences from representatives of the genus Beltanelliformis Menner, 1974. It was shown that the taxon B. konovalovi, most likely, does not belong to this genus and probably needs further revision, and, in turn, the fossil locality at the Shirokovskii Reservoir allows us to establish a new area with fossils of the Precambrian mobile organisms.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070061

The Ura Uplift section in the Patom Highlands area of Siberia is one of the most complete Neoproterozoic carbonate-siliciclastic succession with excellent chemostratigraphic records (d13C and 87Sr/86Sr). Present study reveals the first finds of Ediacaran macrofossils within thick siliciclastic/carbonate succession of the Chencha and Zherba formations with well-established negative d13C anomaly attributed to the Shuram Excursion in this section. The fossils are preserved in glauconitic and quartz sandstone horizons in shallow-marine tide-influenced nearshore environment and share many taphonomic and morphological features with the White Sea-and Nama-type biotas. On the one hand, stratigraphic position of some of fossils within the uppermost Shuram Excursion falls into the time interval-573-567 Ma and therefore is correlative to the Avalon-type fossil assemblage. On the other hand, the new fossil assemblage indicates to the earlier appearance of some Nama-type species, such as erniettomorphs, than it was thought. In addition, the new assemblage is characterised by low-diversity metazoan community dominated by microbial textures. It potentially supports the hypothesis that the Ediacaran shallow water fossil assemblages were significantly less species-rich than their deeper water counterparts. The discovery of the old -est macrofossils in South Siberia both opens a new window to understand their palaeoecology and taphonomy, and demonstrates that palaeontological potential of such a vast region has not entirely been realised. (c) 2023 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Macroscopic fossils as composite molds and casts of Ediacara-type soft-bodied organisms were found in the Dzhezhim Formation of the Timan Range for the first time. Among them, representatives of palaeopascichnids, arboreomorphs, chuariomorphids, microbial colonies, and trace fossils were identified. This finding of such a large number of various Ediacaran fossils on the Timan Range not only develops our understanding of their paleogeographic range but also clarifies the age limits of the deposition of the Dzhezhim Formation, the stratigraphic position of which in the Upper Precambrian section was controversial.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070413

Macrofossils of the Vendian soft-bodied organisms were found for the first time in the Vizinga and Ust’-Palega formations of the Upper Precambrian in Chetlasskii Kamen Hill (Middle Timan, Arkhangelsk oblast). Representatives of palaeopascichnids, aspidellamorphs, and possible frondomorphs, trace fossils, and microbially induced arumberiamorph structures were identified among molds and three-dimensional casts of fossils. Previously we revealed Vendian macrofossils in the Upper Precambrian in Dzhezhim-Parma Hill (South Timan, Komi Republic). The discovery of one more locality of various Ediacaran fossils in the middle part of the Timan Ridge significantly expands their paleogeography and also clarifies the time frame of deposition of the Vizinga and Ust’-Palega formations, the position of which in the Upper Precambrian section of Central Timan was debatable.

A cyclostratigraphic study of the Late Precambrian Zhuya Group (Nikolskoye and Chencha Formations), and Torgo formation in the southern part of the Siberian Platform was carried out to determine the duration of the C-isotope anomaly imprinted in them. The similarity of the ratios of the period lengths of the cyclic components of the magnetic susceptibility in the coeval deposits of the remote sections of the Nikol’skoye and Torgo Formations indicates the connection between the revealed cyclicity and the basin-scale environment changes. According to the astrochronological model, the duration of the formation of the studied intervals of the Nikol’skoye (57 m) and Chencha (147 m) formations was 850 and 2500 ky, respectively. Extrapolation of the data obtained shows that the duration of the C-isotope anomaly of the Zhuya Group in the Vendian reference section on the Ura uplift was about 10 My, which is consistent with most estimates of the Shuram anomaly’s duration and its stratigraphic analogues.

One of the hypotheses, explaining a sudden vanishing of the Ediacaran biota at the Ediacaran-Cambrian transition, correlates this phenomenon with a disappearance of specific taphonomical factors providing fossilization of soft-bodied organisms ('Cheshire Cat' hypothesis). The terminal Ediacaran-Lower Cambrian fossil record does reveal a progressive development of bioturbation and associated decrease of microbial mats, which played a crucial role in the late Precambrian ecosystems. But the tempo of the evolution of organism-sediment interactions significantly varied between different zones of marine basins. Hence, if the 'Cheshire Cat' hypothesis is correct, the sedimentary environments barely (if any) colonized by the burrowing eumetazoans might provide the unique interplay of conditions for habitat and Ediacara-style preservation of soft-bodied organisms even in the early Cambrian. Herein we present the new carbon isotope data calibrating the Terreneuvian record in the Ura Uplift of South Siberia and also report fossilized soft-bodied organisms morphologically-close to the Ediacaran holdfasts preserved in association with microbially-induced sedimentary structures in the Cambrian Stage 2 carbonate-siliciclastic Nokhtuisk Formation. Although the late Terreneuvian age, this marginal marine succession is poorly bioturbated and hosts the soft-bodied fossils in the intervals undisturbed by the burrowing organisms. Our study demonstrates the possibility of Ediacara-style preservation of soft-bodied organisms in specific habitat and taphonomic conditions until being replaced by the Cambrian endobenthos.

A cyclostratigraphic study of the Late Precambrian Zhuya Group (Nikolskoye and Chencha Formations) and Torgo formation in the south of the Siberian Platform was carried out to determine the duration of the C-isotope anomaly imprinted in them. The similarity of the ratios of the period lengths of the cyclic components of the magnetic susceptibility in the coeval deposits of the remote sections of the Nikol’skoye and Torgo Fms. indicates the connection between the revealed cyclicity and the basin-scale environment changes. According to the obtained astrochronological model, the duration of the formation of the studied intervals of the Nikol’skoye (57 m) and Chencha (147 m) formations was 850 and 2500 ky, respectively. Extrapolation of the data obtained shows that the duration of the C-isotope anomaly of the Zhuya Group in the Vendian reference section of the on the Ura uplift was about 10 My, which is consistent with most estimates of the Shuram anomaly’s duration and its stratigraphic analogues.

The siliciclastic succession of the Ediacaran Chernyi Kamen Formation in the Central Urals of Russia contains a rich complex of Ediacaran fossils that represent in situ benthic populations buried in life position. The present work reports Beltanelliformis konovalovi sp. nov. found as a paleocommunity of organisms and studied for their morphology and spatial distribution. Unlike the type species (B. brunsae), new fossils are preserved within fine-grained sandstone beds as three-dimensional pancake-like or flattened discoidal single, paired, or occasionally aggregated bodies with an ultra-thin rim. Statistical analysis shows significant predominance of small individuals in the paleocommunity, which in turn manifests different spatial distribution in comparison with larger ones. In addition, the studied paleocommunity exhibits patterns of self-organization in extremely shallow marine environment and adaption to periodic desiccation. These results provide quantitative support for the more complex ecology of Beltanelliformis and also expand the range of taphonomic possibilities of macroscopic life in the terminal Neoproterozoic.

Palaeopascichnida is a problematic group of extinct organisms that is globally distributed in Ediacaran sequences of Avalonia, Baltica, Siberia, South China and Australia. The fossils related to Palaeopascichnida consist of serially or cluster-like arranged, millimetre- to centimetre-scale globular or allantoid chambers, which are characterized by substantial differences in preservation, leading to no consistent diagnosis for these organisms. Here we integrate morphometric variation, stratigraphic distribution and habitat settings of more than 1200 specimens from all known fossil localities. The results of the morphological analysis demonstrate variation in chamber shape and size, and allow us to recognize six valid species within the group. Statistical analysis of the specimen distribution with respect to sedimentary environments indicates a significant difference in palaeoecological settings between species, making a significant contribution to the evolution and systematic palaeontology of these problematic organisms and perspective on their use in Neoproterozoic biostratigraphy. Our revision and systematic study sheds new light on one of the least studied groups of the late Ediacaran biota.

Fossil material of Ediacaran macroscopic algae has been found in the Vendian reference section, in the upper part of the Dal’nyaya Taiga Group of the Ura uplift, in the southern part of the Siberian Platform. The macrofossils discovered in the upper part of the Dal’nyaya Taiga Group are morphologically similar to carbonaceous Miaohen biota from the Ediacaran of South China; however, they occupy a lower stratigraphic level. Hence, the finding of algae macrofossils both develops our understanding of the evolution of marine ecosystems in the Proterozoic and demonstrates that the paleontological potential of one of the most representative Upper Precambrian sections has not been fully plumbed.

In 2020–2021 the palaeopascichnid fossils were found in the Krasnaya Gorka Site (Shirokovsky Reservoir, Kosva River area, Perm Region), a type Vendian fossil locality (problematic discoidal casts and arumberiamorph structures) for the Central Urals discovered by Yu.R. Bekker in 1972. In the stratigraphical context, the fossil locality is associated with Chernyi Kamen Formation of the Upper Vendian Sylvitsa Group. The results of morphometric analysis of palaeopascichnid fossils made possible to distinguish three morphological types: Palaeopascichnus delicatus, Yelovichnus gracilis, and Palaeopascichnus linearis. Finding of a large number of palaeopascichnid fossils both develops the understanding of their palaeobiology and taphonomy, and also demonstrates that palaeontological potential of the type fossil locality and one of the most representative section of the Chernyi Kamen Formation has not entirely been realized.

The broad-scale environment plays a substantial role in shaping modern marine ecosystems, but the degree to which palaeocommunities were influenced by their environment is unclear. To investigate how broad-scale environment influenced the community ecology of early animal ecosystems we employed spatial point process analyses to examine the community structure of seven bedding-plane assemblages of late Ediacaran age (558–550 Ma), drawn from a range of environmental settings and global localities. The studied palaeocommunities exhibit marked differences in the response of their component taxa to sub-metre-scale habitat heterogeneities on the seafloor. Shallow-marine palaeocommunities were heavily influenced by local habitat heterogeneities, in contrast to their deep-water counterparts. Lower species richness in deep-water Ediacaran assemblages compared to shallow-water counterparts across the studied time-interval could have been driven by this environmental patchiness, because habitat heterogeneities correspond to higher diversity in modern marine environments. The presence of grazers and detritivores within shallow-water communities may have promoted local patchiness, potentially initiating a chain of increasing heterogeneity of benthic communities from shallow to deep-marine depositional environments. Our results provide quantitative support for the “Savannah” hypothesis for early animal diversification – whereby Ediacaran diversification was driven by patchiness in the local benthic environment. Author Contributions E. Mitchell conceived this paper and wrote the first draft. N. Bobkov, A. Kolesnikov, N. Sozonov and D. Grazhdankin collected the data for DS surface. N. Bobkov and N. Sozonov performed the analyses on DS surface. N. Bykova, S. Xiao, and D. Grazhdankin collected the data for WS, KH1 and KH2 surfaces and E. Mitchell performed the analyses. A. Dhungana and A. Liu collected the data for FUN4 and FUN5 surfaces and A. Dhungana performed the analyses. T. Mustill and D. Grazhdankin collected the data for KS and T. Mustill and E. Mitchell performed the analyses. I. Hogarth developed the software for preliminary KS surface analyses. E. Mitchell, N. Bobkov, N. Bykova, A. Dhungana, A. Kolesnikov, A. Liu, S. Xiao and D. Grazhdankin discussed the results and prepared the manuscript.

Dickinsonia in the central Urals occurs in a succession transitional from marginal marine to non-marine. Even within this sequence Dickinsonia appears to be restricted to the least marine facies interpreted as a coastal lagoon surrounded by tidal flats. Another puzzling aspect is the complete absence of other Ediacaran taxa that are usually found together with Dickinsonia in other fossil localities. In fact, the Sinii Kamen Member of the Cherny Kamen Formation yielded an assemblage of Ediacaran macrofossils including aspidellamorph and mawsonitomorph holdfasts, frondomorphs, palaeopascichnids, and concentric ring structures of microbial origin; however, fossils of Dickinsonia have never been found in this association.

espanolEl Grupo de Asha de los Urales meridionales, inicialmente definido por Albert Olli como complejo sedimentario paleozoico, hace mas de medio siglo, fue considerado como una seccion clave para el Vendico (Ediacarico) de la vertiente occidental de los Urales meridionales. Sin embargo, secuencia sedimentaria terrigena de unos 1.700 m de espesor se caracteriza por una biodiversidad inusualmente baja de macrofosiles ediacaranos, lo que podria explicarse por la edad relativamente temprana del grupo y el posible evento de extincion masiva que marca el final del periodo Ediacarico. La edad relativamente temprana fue confirmada por la datacion de 547.6±3.8 Ma obtenida de una toba en la parte inferior de la Formacion de Basa, asi como por el hallazgo de la iconospecie Didymaulichnus tirasensis en la parte superior de la Formacion de Zigan. Sin embargo, en 2018 se ha documento la aparicion masiva de D. tirasensis en la parte mas baja de la Formacion de Basa. Por lo tanto, la edad Vendico (Ediacarico) del Grupo de Asha de los Urales meridionales puede ser reconsiderada en favor del Ediacarico terminal-Cambrico o incluso del Cambrian temprano. EnglishThe Asha Group of the South Urals, initially erected by Albert Olli as Palaeozoic sedimentary complex, more than half a century ago was considered as a key section for the Vendian (Ediacaran) of the western slope of the South Urals. However, the ca. 1700 m-thick terrigenous sedimentary sequence is characterised by unusual low biodiversity of Ediacaran macrofossils, which might be explained by relatively young age of the Asha Group and possible mass extinction event in the end of Ediacaran Period. The relatively young age was confirmed by the U-Pb zircon date of 547.6±3.8 Ma obtained from the tuff in the lower part of the Basa Formation as well as finding of ichnospecies Didymaulichnus tirasensis in the upper part of Zigan formation. However, in 2018 it has been documented there the mass appearing of D. tirasensis in the lowermost part of the Basa Formation. Therefore, the Vendian (Ediacaran) age of the Asha Group of the South Urals can be revisited in favour to terminal Ediacaran- Cambrian or even early Cambrian.

Durante más de cuarenta años, los paleopasciquínidos han representado un grupo enigmático de fósiles macroscópicos, caracterizados por diferencias sustanciales en la conservación, lo que no conduce a un diagnóstico consistente de estos organismos. Los fósiles de paleopasciquínidos se encuentran distribuidos globalmente en las secuencias ediacáricas de la Plataforma de Europa Oriental, Avalonia, China meridional, Siberia y Australia. A la luz de una nueva perspectiva para reanimar el “Véndico” como una serie superior formal del Sistema Ediacárico, los paleopasciquínidos son probablemente el único grupo fósil ediacárico cuyo rango estratigráfico abarca casi toda la “Serie del Véndico”. Además, se ha considerado que los paleopasciquínidos se encuentran entre los macroorganismos más antiguos conocidos con un esqueleto aglutinado; su presencia enfatiza este grupo en términos de bioestratigrafía y correlación geológica ediacárica y allana el camino para la reexaminación de otros fósiles esqueléticos de tipo paleopasciquínido.

Research subject. This article presents new data on carbonate facies of the upperUk subformation, Upper Riphean of theSouth Urals. A particular attention is paid to the distribution of rare-earth elements (REE) and yttrium (Y) in stromatolitic and intraclastic limestones and calcareous shales (bulk samples and their acetic acid leachates).Materials and methods. We have studied lithological features of limestones in the geological section and in thin sections. The contents of trace elements in rocks were determined by the ICP-MS method at the IGG UB RAS (Yekaterinburg), the composition of organic matter was determined at the IPGG SB RAS (Novosibirsk) by gas-liquid chromatography and chromatography-mass spectrometry.Results. The most representative section of the Upper Uk Subformation located along the eastern edge of the town Ust-Katav can be subdivided into several members of different lithology and thickness: (1) biohermdominated member comprising large microbialitic build-ups and inter-bioherm sediments (intraclastic limestones, calcareous biolaminites); (2) transitional member characterised by small bioherms alternating with other carbonates; (3) interbedded coarseand fine-grained limestones. The presence of molar-tooth structures in the carbonate rocks of Uk Formation made it possible to constrain the age of thisUpper Riphean formation to pre-CryogenianConclusions. There are similarities in REE and Y distribution in both clean (devoid of siliciclastic component) bulk limestone samples and in their acetic acid leachates. PAAS-normalised REE + Y patterns demonstrate positive La, Gd, Y anomalies and negative Eu, Ce anomalies. The latter suggest marine depositional environments for theUpper Uk stromatolitic limestones. The results of the pioneering research into the composition of bitumens and biomarkers from the Upper Uk Subformation have shown that carbonates and shales are depleted in the organic matter. The source material for the organic matter was provided by two types of communities comprising both eukaryotes and prokaryotes and inhabiting well aerated environment, perhaps with lowered salinity of marine water.

espanolLos ejemplares de Dickinsonia de los Urales Centrales se caracterizan por una clara simetria bilateral. Tomando en cuenta las observaciones de especimenes australianos, consideramos que la llamada’simetria de reflexion por deslizamiento’ en estos fosiles es un fenomeno tafonomico. El grafico de distribucion de frecuencias de tamano muestra el predominio de individuos juveniles en la poblacion estudiada de Dickinsonia de los Urales Centrales. Asumiendo que la edad de un individuo se manifiesta por su tamano, existe un predominio significativo de individuos juveniles en la poblacion. Se pueden prever tres escenarios posibles: (1) la poblacion tiene un gran numero de individuos juveniles como resultado de la alta tasa de supervivencia en la zona intermareal; (2) la poblacion esta dominada por formas juveniles porque esta enterrada inmediatamente despues de la eclosion; (3) suponiendo que Dickinsonia fuera un organismo movil activo, la abundancia de individuos juveniles podria explicarse por su incapacidad para escapar del entierramiento (aunque es dificil imaginar que algunos de los individuos maduros esten enterrados con signos de comportamiento de escape); y (4) la poblacion podria interpretarse como un “lugar de nidificacion” fosilizado para Dickinsonia en la zona intermareal, donde las formas juveniles maduraron antes de migrar a la zona submareal. La poblacion de estudio puede caracterizarse como en expansion o estable; por lo tanto, el entorno intermareal puede describirse como favorable para estos organismos EnglishSpecimens of Dickinsonia from the Central Urals are characterised by clear bilateral symmetry. Taking into account observations from Australian specimens, we consider that the so called ‘glide reflection symmetry’ in these fossils is a taphonomic phenomenon. The size frequency distribution plot shows the predominance of smaller individuals in the studied population of Dickinsonia from the Central Urals. Assuming that the age of an individual is manifested in the body size, there is a significant predominance of juvenile individuals in the population. Three possible scenarios can be envisaged: (i) the population has a large number of juvenile individuals as the result of high survivorship rate in the intertidal zone; (ii) the population teems with juvenile forms because it is buried immediately after hatching; (iii) assuming that Dickinsonia was an actively motile organisms, that abundance of juvenile individuals could be explained by their inability to escape burial (although it is difficult to imagine that some of the mature individuals are buried with signs of escape behaviour); and (iv) the population could be interpreted as a fossilised ‘nesting ground’ for Dickinsonia in the intertidal zone where juvenile forms underwent maturation before migrating back to the subtidal zone. The study population can be characterised as expanding or stable; therefore, the intertidal setting can be described as favourable for these organisms.