Search

The classical lower-middle Cambrian boundary is approximately equivalent with the boundary of the Cambrian Series 2 and 3, which is now in the process of definition by the International Subcommission on Cambrian Stratigraphy. Currently, there are two oryctocephalid trilobite species first appearance data (FAD) that are suggested as possible markers of this level: Ovatoryctocara granulata Tchernysheva, 1962 and Oryctocephalus indicus (Reed, 1910), respectively. Until now neither of these two species has been recorded in the Mediterranean subprovince or Baltica. As a result, in these regions a level potentially correlating with either the FAD of Ovatoryctocara granulata or Oryctocephalus indicus has to be located using the available bio-, isotope-, and event-stratigraphy data. Carbon isotope signatures reveal global oceanic perturbations adjacent to the Cambrian Series 2 and Series 3 (former lower-middle Cambrian) boundary. This event, first called the Valdemiedes Event (it was defined in Murero, NE Spain; Liñán et al., 1993a), caused a noticeable extinction of trilobites, mostly olenellids and protolenids (which were replaced in some regions by paradoxidids), as well as an almost complete extermination of some other early Cambrian marine animals. Both isotope and palaeontological evidence show that the disappearance of olenellids in Laurentia, protolenids in Siberia and the appearance of the first Acadoparadoxides in Western Gondwana, Baltica, Avalonia, and Siberia, which was formerly thought to be a series of diachronous regional perturbations, were nearly contemporaneous events. Features of a global ecological crisis and faunal replacement being taken together with a pronounced global δ13Corg negative excursion would serve as the best indicator of the lower boundary of the Cambrian Series 3 and Stage 5 in the Mediterranean subprovince and is correlatable with the Ovatoryctocara granulata FAD. Another δ13Corg negative excursion followed by a positive shift occurs at a slightly younger level, which coincides with a transgression maximum and roughly is coeval with the Oryctocephalus indicus FAD, also proposed as a possible base of the Cambrian Series 3. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Y. Cai & H. Hua comment: Zhuravlev, Gámez Vintaned & Ivantsov (2009) reported the problematic Ediacaran fossil Gaojiashania annulucosta in Siberia and they considered that this is the first find of Gaojiashania outside China, since Gaojiashania had previously only been reported from the Gaojiashan Member of the middle Dengying Formation in the Ningqiang area, southern Shaanxi Province, South China. However, we believe that the so-called Siberian Gaojiashania was mis-identified, and what was described as Gaojiashania annulucosta by Zhuravlev, Gámez Vintaned & Ivantsov (2009) is more appropriately ascribed to Shaanxilithes ningqiangensis, another problematic Ediacaran fossil that has also been known from the Gaojiashan Member in Shaanxi Province of South China (Chen, Chen & Lao, 1975; Xing et al. 1984), as well as the stratigraphically equivalent Taozichong Formation in Guizhou Province (Hua, Chen & Zhang, 2004) and the Jiucheng Member (Dengying Formation) in Yunnan Province of South China (Zhu & Zhang, 2005), the Zhoujieshan Formation in Qinghai Province (Shen et al. 2007), and the Zhengmuguan Formation in Ningxia Hui Autonomous Region of North China (Shen et al. 2007). [ABSTRACT FROM AUTHOR]

A quantitative compilation of carbonate skeletal mineralogy through the Phanerozoic shows a progressive replacement of low-Mg calcite by aragonite. This general trend overrides the subsidiary trend of greenhouse intervals favoring biogenic low-Mg calcite mineralogies (calcite seas), and icehouse intervals facilitating aragonite + high-Mg calcite mineralogies (aragonite seas). The replacement of low-Mg calcite by aragonite was, however, achieved episodically at mass extinction intervals. In particular, the end-Permian extinction both preferentially removed species bearing "unfavorable" low-Mg calcite, and allowed the selective radiation of biota with "favorable" aragonite. This demonstrates the importance of incumbency in the evolution of skeletal mineralogy. We suggest that the broad increase of aragonitic biota has been controlled by changes in atmospheric carbon dioxide partial pressure (pCO2) via carbonate mineral kinetics. Through the Phanerozoic, broadly decreasing pCO2 levels led to decreasing total alkalinity and dissolved inorganic carbon, and increasing oceanic pH. Superimposed upon this general trend, there are cyclic episodes of relatively high pCO2 and saturation state combined with a lower ratio of magnesium to calcium ions in seawater driven by the relatively slow changes in mid-ocean ridge expansion rates. Mass extinction events, many of which may have been caused by rapid global changes in temperature and/or pCO2, represent major intervals of turnover. [ABSTRACT FROM AUTHOR]

The paper is concerned with the issues of modeling dynamic systems with interval parameters. In previous works, the authors proposed an adaptive interpolation algorithm for solving interval problems; the essence of the algorithm is the dynamic construction of a piecewise polynomial function that interpolates the solution of the problem with a given accuracy. The main problem of applying the algorithm is related to the curse of dimension, i.e., exponential complexity relative to the number of interval uncertainties in parameters. The main objective of this work is to apply the previously proposed adaptive interpolation algorithm to dynamic systems with a large number of interval parameters. In order to reduce the computational complexity of the algorithm, the authors propose using adaptive sparse grids. This article introduces a novelty approach of applying sparse grids to problems with interval uncertainties. The efficiency of the proposed approach has been demonstrated on representative interval problems of nonlinear dynamics and computational materials science. [ABSTRACT FROM AUTHOR]

The evaluation of microwave (MW) imaging radar capabilities in non-destructive tests to detect internal structures or defects in the inner volume of thermal insulation coating has been carried out. The MW imaging with high spatial resolution has been performed with holographic subsurface radar operated in the frequency range from 22.2 to 26.2 GHz. The investigation of this non-destructive testing (NDT) technology is important to evaluate the feasibility for quality check of assembled polyurethane sandwich parts for thermal insulation. The samples of polyurethane foam thermal insulation have been fabricated in collaboration with a manufacturing industry of household appliances to have a representative set of real defects. The images obtained are of high quality and easy to be interpreted as they reveal the shapes and plane positions of the defect into samples with thickness up to 90 mm. • Microwave NDT of thermal insulating materials. • Microwave imaging with 22 GHz holographic subsurface radar. • Defects detection by high resolution imaging. • NDT investigation of polyurethane foam thermal insulation materials. • Detection and reconstruction of microwave holograms. [ABSTRACT FROM AUTHOR]

A lack of effective non-contact methods for automatic fall detection, which may result in the development of health and life-threatening conditions, is a great problem of modern medicine, and in particular, geriatrics. The purpose of the present work was to investigate the advantages of utilizing a multi-bioradar system in the accuracy of remote fall detection. The proposed concept combined usage of wavelet transform and deep learning to detect fall episodes. The continuous wavelet transform was used to get a time-frequency representation of the bio-radar signal and use it as input data for a pre-trained convolutional neural network AlexNet adapted to solve the problem of detecting falls. Processing of the experimental results showed that the designed multi-bioradar system can be used as a simple and view-independent approach implementing a non-contact fall detection method with an accuracy and F1-score of 99%. [ABSTRACT FROM AUTHOR]

Evidence of the Frasnian Genundewa Event at the FZ 2 – FZ 3 boundary interval has been detected in the facies of the isolated carbonate platform in Subpolar Urals. The preserved traces of the Genundewa Event represent micritic microlaminated carbonates, which manifests a short-term deepening episode in an extremely shallow water background. From the onset of this deep-water deposition there is a dominance of Polygnathus, Ancyrodella, and Mesotaxis whereas in the underlying shallow water deposits, the genus Polygnathus clearly predominated. No specific features of the Genundewa Event were observed in the C-isotope record. The mean δ13Ccarb value is approximately 2‰ in the event interval. The onset of the Genundewa Еvent corresponds to the beginning of Euro-American IIb-2 cycle and is correlated with the base of the Sargaevian regional substage of the Urals and Russian Platform, as well as the base of Poland IC cycle. This correlation confirms the global character of this event. [ABSTRACT FROM AUTHOR]

Archaeocyaths were one of the major animal groups contributing to the Cambrian Explosion. Despite an overall poriferan appearance of their hypercalcified skeletons, they exhibit a number of peculiar features such as the presence of septa and an absence of spicules. This sets archaeocyaths apart from general trends in early poriferan evolution. Fossils recently discovered from the early Cambrian Guanshan Lagerstätte of South China exhibit features typical for the suborder Archaeocyathina whilst possessing a silicified skeleton associated with carbonaceous material. This rigid fibrous skeletal framework, on the other hand, fits the diagnosis of the supposed ancestral aspiculate demosponges, the family Vauxiidae. By a detailed description of this specimen and a direct morphological comparison between the Archaeocyathina and the Vauxiidae, we suggest that the supposed Cambrian representatives of horny demosponges, that is, vauxiids, probably, were a progeny lineage of archaeocyathines. They survived the extinction of hypercalcified archaeocyaths due to their ecological adaption to siliciclastic environments. The existence of hypercalcified dictyoceratid ('keratosan') sponge Vaceletia, well known as a 'living archaeocyath', supports such a possibility. [ABSTRACT FROM AUTHOR]

X-ray computed microtomography (CT) of impact rock varieties from the Kara astrobleme is used to test the method's ability to identify the morphology and distribution of the rock components. Three types of suevitic breccias, clast-poor melt rock, and a melt clast from a suevite were studied with a spatial resolution of 24 µm to assess CT data values of 3D structure and components of the impactites. The purpose is first to reconstruct pore space, morphology, and distribution of all distinguishable crystallized melt, clastic components, and carbon products of impact metamorphism, including the impact glasses, after-coal diamonds, and other carbon phases. Second, the data are applied to analyze the morphology and distribution of aluminosilicate and sulfide components in the melt and suevitic breccias. The technical limitations of the CT measurements applied to the Kara impactites are discussed. Because of the similar chemical composition of the aluminosilicate matrix, glasses, and some lithic and crystal clasts, these components are hard to distinguish in tomograms. The carbonaceous matter has absorption characteristics close to air, so the pores and carbonaceous inclusions appear similar. However, X-ray microtomography could be used to prove the differences between the studied types of suevites from the Kara astrobleme using structural-textural features of the whole rock, porosity, and the distributions of carbonates and sulfides. [ABSTRACT FROM AUTHOR]

We describe aggregative microconchid (Lophophorata) tubes from the uppermost Permian (upper Changhsingian) and Lower Triassic (Olenekian) lacustrine and fluvial strata of the Tunguska and Kuznetsk basins and the southern Cis-Urals, Russia. These attach to clam shrimp carapaces, bivalve shells, terrestrial plant fragments and a horseshoe crab head shield, and also form their own monospecific agglomerations. Planispiral tubes of a wide size range (0.1–2.5 mm) create dense settlements on these firm substrates, which likely comprise multiple generations of the same species. These finds confirm that this extinct lophophorate group was inhabiting non-marine continental basins during latest Permian and earliest Triassic time, when they were major suspension feeders in such limnic ecosystems. Microconchids dispersed extensively and rapidly in the aftermath of the Permian–Triassic mass extinction into both marine and continental basins at low and moderately high latitudes, which were notably different in salinity, temperature, depth and redox conditions. This confirms that small lightly calcified microconchids were a genuine disaster eurytopic group, whose expansion may have been promoted by low predator pressure and low competition for substrate. [ABSTRACT FROM AUTHOR]

Nematomorpha (hairworms) is a phylum of parasitic ecdysozoans, best known for infecting arthropods and guiding their hosts toward water, where the parasite can complete its life cycle. Over 350 species of nematomorphs have been described, yet molecular data for the group remain scarce. The few available mitochondrial genomes of nematomorphs are enriched with long inverted repeats, which are embedded in the coding sequences of their genes—a remarkably unusual feature exclusive to this phylum. Here, we obtain and annotate the repeats in the mitochondrial genome of another nematomorph species—Parachordodes pustulosus. Using genomic and transcriptomic libraries, we investigate the impact of inverted repeats on the read coverage of the mitochondrial genome. Pronounced drops in the read coverage coincide with regions containing long inverted repeats, denoting the 'blind spots' of short-fragment sequencing libraries. Phylogenetic inference with the novel data reveals multiple disagreements between the traditional system of Nematomorpha and molecular data, rendering several genera paraphyletic, including Parachordodes. [ABSTRACT FROM AUTHOR]

Why large and diverse skeletons first appeared ca 550Ma is not well understood. Many Ediacaran skeletal biota show evidence of flexibility, and bear notably thin skeletal walls with simple, non-hierarchical microstructures of either aragonite or high-Mg calcite. We present evidence that the earliest skeletal macrobiota, found only in carbonate rocks, had close soft-bodied counterparts hosted in contemporary clastic rocks. This includes the calcareous discoidal fossil Suvorovella, similar to holdfasts of Ediacaran biota taxa previously known only as casts and moulds, as well as tubular and vase-shaped fossils. In sum, these probably represent taxa of diverse affinity including unicellular eukaryotes, total group cnidarians and problematica. Our findings support the assertion that the calcification was an independent and derived feature that appeared in diverse groups where an organic scaffold was the primitive character, which provided the framework for interactions between the extracellular matrix and mineral ions. We conclude that such skeletons may have been acquired with relative ease in the highly saturated, high alkalinity carbonate settings of the Ediacaran, where carbonate polymorph was further controlled by seawater chemistry. The trigger for Ediacaran biomineralization may have been either changing seawater Mg/Ca and/or increasing oxygen levels. By the Early Cambrian, however, biomineralization styles and the range of biominerals had significantly diversified, perhaps as an escalating defensive response to increasing predation pressure. Indeed skeletal hard parts had appeared in clastic settings by Cambrian Stage 1, suggesting independence from ambient seawater chemistry where genetic and molecular mechanisms controlled biomineralization and mineralogy had become evolutionarily constrained. [ABSTRACT FROM AUTHOR]

The western Mongolian Lake Zone was a Neoproterozoic to early Paleozoic volcanic arc where tuffs, lavas, fossiliferous siliciclastics, and carbonates accumulated during the early Cambrian. An uppermost Cambrian Series 2 (upper Stage 4) trilobite assemblage is described here from the Burgasutay Formation representing a continuous lower Cambrian succession at the Seer Ridge of the Great Lake Depression. The new assemblage is dominated by dorypygids and consists of 13 trilobite genera belonging to nine families including Catinouyia heyunensis new species. These fossils comprise the youngest and richest lower Cambrian trilobite assemblage in Mongolia. The composition of the Lake Zone fauna suggests its biogeographic affinity with the Siberian Platform and Altay-Sayan Foldbelt, but the presence of inouyiids also implies a connection of this region with East Gondwana. UUID: http://zoobank.org/fb0ebe23-144f-46ed-9543-7df9eea85fbc [ABSTRACT FROM AUTHOR]

Archaeocyaths were among the iconic metazoans of the early Cambrian seas and dominated the earliest Phanerozoic reef system before their dramatic decline toward the end of the early Cambrian time (c. 510 million years ago (Ma)). Over their almost 200-year research history, these organisms have been recognized as stenobionts adapted to a very narrow range of carbonate-dominated environments. Here, for the first time, we report three sorts of archaeocyath-like fossils from the Chengjiang Biota (c. 518 Ma), which was developed on a siliciclastic shelf devoid of any reefal buildups. These fossils are preserved in storm-induced mudstone without evidence of fragmentation during transportation. All of them share the same preservation mode involving replacement by clay minerals and iron oxides but exhibit archaeocyath-type external skeletal features. One species, which used to be interpreted as a dasycladalean alga, shows an aquiferous system and a skeletal ontogeny that is typical of archaeocyaths. It can be assigned to Propriolynthus sp. The other two species are comparable with representatives of the superfamily Ethmocoscinoidea and the family Sigmocyathidae, respectively. Propriolynthus sp. represents the first recognized one-walled archaeocyath in South China and fills a missing link in the migration route of one-walled archaeocyaths, although not in the phase of a reef-builder or dweller. This data reveals new aspects of archaeocyath evolution by niche expansion into siliciclastic-dominated seas at the acme of their diversification. • The first discovery of ahermatypic archaeocyaths that adapted to siliciclastic environments. • The first report of one-walled archaeocyaths in South China. • It reveals a new mechanism in archaeocyathan evolution and global spreading: niche expansion during the migration. [ABSTRACT FROM AUTHOR]

The article presents a study which explores the skeletal marine invertebrate phyla appeared during the Cambrian explosion, except for Bryozoa with mineralized skeletons, which first appear in the Early Ordovician. It mentions that skeletal diversity of Early Ordovician bryozoans suggests a preceding interval of diversification.

New assemblages of skeletal fossils chemically extracted from carbonates of the Cambrian Stage 2-Drumian Stage are reported from the lower reaches of the Lena River as well as from the Khorbusuonka, Malaya Kuonamka, and Bol'shaya Kuonamka rivers in northern part of the Siberian Platform. The fauna studied with scanning electron microscopy includes brachiopods, molluscs, hyoliths, halkieriids, chancelloriids, tommotiids, lobopodians, palaeoscolecidans, bradoriids, echinoderms, anabaritids, hyolithelminths, and sponges showing similarity to previously described fossil assemblages from Siberia, Laurentia, and Gondwana. The material includes emended descriptions of Halkieria proboscidea, Hadimopanella knappologica, Archaeopetasus typicus, and first descriptions of Hadimopanella foveata Kouchinsky sp. nov. and Archaeopetasus pachybasalis Kouchinsky sp. nov. Affinity of Archaeopetasus to chancelloriids is suggested. Finding of an in-place operculum in a planispiral shell of Michniakia minuta enables reinterpretation of this form as a hyolith, not a mollusc. The cambroclavids Cambroclavus sp. and Zhijinites clavus and the earliest echinoderms belonging to the Rhombifera and Ctenocystoidea are reported respectively from the lower Botoman stage and Botoman-Toyonian transitional beds, correlated with Cambrian Stage 4. Carbon isotopes are analysed from sections of the Chuskuna (upper Kessyusa Group), Erkeket, Kuonamka, Olenyok, Yunkyulyabit-Yuryakh, Tyuser and Sekten formations. A major part of the Î'13C record is obtained from the Cambrian Stage 4-Drumian Stage strata which remain incompletely characterised by chemostratigraphy. The Lower Anomocarioides limbataeformis Carbon isotope Excursion (LACE) from the Drumian Stage of the Khorbusuonka River is introduced herein. New chemostratigraphic data are used for regional and global correlation and facilitate study of the evolutionary development of animals and faunas through the "Cambrian explosion". [ABSTRACT FROM AUTHOR]

Mammal remains preserved in the permafrost zone often bear traces of postmortem transformations, reflecting aspects of the palaeoenvironment and the processes that took place during the accumulation of host sediments. Multidisciplinary studies including radiocarbon dating, infrared spectroscopy, and microfossil analyses and grain size of infilling sediments from remains allow recognition of their stratigraphical and palaeogeographical origins and facilitate reconstructions of taphonomic pathways and the pre‐burial environments. Here, as exemplified by skulls of woolly rhinoceros, cave lion, and ancient bison, some distinct features of postmortem changes such as nonpyrogenic charring and vivianite encrustation indicate that the remains have undergone a complex range of burial processes in aerobic and anaerobic conditions in the Pleistocene landscapes of Arctic northeastern Russia. We hypothesize that these processes were mainly confined to the warmer intervals in the Late Pleistocene. [ABSTRACT FROM AUTHOR]

The Lower Mississippian δ13Ccarb excursion is one of the largest in the Phanerozoic, reaching ≥+7‰ in parts of western North America. Two new sections analyzed in Belgium and the Ural Mountains record the event, but peak values are ≤+5.5‰. The presence of key conodont zones allows for good correlation between Europe and North America, and indicates that a major time gap cannot account for the differences in δ13Ccarb. Patterns of diagenetic alteration are similar among sections and also do not appear to fully explain the lower values in European carbonate. The observed variability of several per mil, which is typical for Paleozoic excursions that are also recorded in epeiric sea carbonates, likely reflects a significant role for local carbon cycling in δ13C of dissolved inorganic carbon. Enhanced regeneration of phosphate under anoxic conditions in western North American basins is interpreted to have increased biological pumping of 12C and locally elevated δ13C relative to mean surface ocean water. The lower δ13C in the European sections is interpreted to be more representative of the global surface oceans, rather than having been influenced by influx of respired 12C during increased water mass residence time on the shelf. The interpretation of the influence of local carbon cycling on δ13Ccarb has implications for calculations of global organic carbon burial rates. Model input of a shift to values of ≥+7‰ predicts steady-state increases in the fraction of carbon buried as organic matter of as much as 50–75‰, assuming no changes in the riverine input. This would require a rapid buildup of extensive global sinks for Corg that could accommodate ∼1.5×1020 g of excess burial above and beyond the steady state during the ∼2 Myr event. However, use of a lower value for δ13Ccarb (closer to the +5.5‰ in European sections) in global models makes it easier to account for carbon storage in basins such as the Antler and related foreland basins of the western margin of Euramerica, in addition to the unknown amounts buried in deep-sea environments during the Early Mississippian. [Copyright &y& Elsevier]

The lower member of the Poleta Formation is well known for its abundant archaeocyaths, including an exceptionally preserved reef at Stewart's Mill in Nevada. Large archaeocyath-bearing reefs are relatively uncommon, with most occurring as small nearshore patch reefs. Here, we describe a new 70 m-thick archaeocyath reef from the lower Poleta Formation, herein referred to as the Gold Point Reef, located near the townsite of Gold Point, Nevada. In spite of broad similarities with the Stewart's Mill exposure, the Gold Point Reef shows an interplay between shoal and reef development over the ~ 70 m exposure that differs from what is observed at Stewart's Mill. This reef also preserves a small shelly fauna in its uppermost 10 m, dominated by Hyolithellus. Three successive ecological stages of reef development are observed here: the pioneer stage characterized by a single rare frame-building species; the diversification stage involving about nine species of both frame-building and mud-sticking archaeocyaths; and the final foundering stage represented by one to two species of archaeocyaths and facies indicating reef demise, including abundant grainstone/packstone shoals and a silicified upper bed with a settlement of hyolitheminthes. During the apex of reef development here, there are large modular archaeocyaths, which were able to produce thick secondary skeletal tissue for a firm attachment; these archaeocyaths were capable of building large reefs in a variety of settings. Additionally, the carbon isotope profile recorded in the Gold Point Reef shows similarities to nearby exposures of the equivalent lower Poleta Formation, with the exception of a small negative downturn at the top of the reef that is not found in other locations. Combined with the documentation of facies changes over short lateral distances, the isotope data suggest that archaeocyathan reefs may have been time-transgressive across the shelf during deposition of the lower Poleta. Additionally, our work suggests that both here and globally, the specific biotic assemblage reflected the local influences of the environment on reef development, creating highly variable coeval paleocommunities even within a restricted area. [ABSTRACT FROM AUTHOR]

Background Crimean-Congo hemorrhagic fever (CCHF) is acute viral infection and a major emerging infectious diseases threat, affecting a large geographical area. There is no proven antiviral therapy and it has a case fatality rate of 4–30%. The natural history of disease and outcomes of CCHF in pregnant women is poorly understood. Objectives To systematically review the characteristics of CCHF in pregnancy, and report a case series of 8 CCHF cases in pregnant women from Russia, Kazakhstan and Turkey. Methods A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement protocol. PubMed, SCOPUS, Science Citation Index (SCI) were searched for reports published between January 1960 and June 2016. Two independent reviewers selected and reviewed studies and extracted data. Results Thirty-four cases of CCHF in pregnancy were identified, and combined with the case series data, 42 cases were analyzed. The majority of cases originated in Turkey (14), Iran (10) and Russia (6). There was a maternal mortality of 14/41(34%) and fetal/neonatal mortality of in 24/41 cases (58.5%). Hemorrhage was associated with maternal (p = 0.009) and fetal/neonatal death (p < 0.0001). There was nosocomial transmission to 38 cases from 6/37 index pregnant cases. Conclusion Cases of CCHF in pregnancy are rare, but associated with high rates of maternal and fetal mortality, and nosocomial transmission. [ABSTRACT FROM AUTHOR]

The upper Frasnian coral biostrome, well-exposed in the Russkiy Brod quarry, Central Devonian Field, Russia, has been studied in detail with respect to paleoecology and sedimentary environment. The biostrome, formed by auloporid tabulates and solitary and colonial rugose corals, originated in an offshore environment characterized by calmer periods with slow or halted sedimentation, and more energetic periods when sedimentation rate increased. The episodic, higher sediment influx and stronger hydrodynamic regime are not only well-expressed in the microfacies, but also in the variability of colony integration of the rugose corals observed even within single coralla. Distinct development of constrictions, rejuvenescences and deflection of growth directions in rugose corallites may also indicate unstable sedimentary conditions. The latter features, however, may have, in part, also resulted from syn vivo biotic interaction with the associated auloporids. Both the facies and paleontological observations suggest that the biostrome originated by the colonization of deposited bioclasts by pioneering auloporids, creating the framework for settlement of later generations of auloporids and rugose corals. Apart from abundant auloporids representing a single species and associated rugose corals, the other encrusters are not numerous and poorly diversified, represented by dominating foraminifers, followed by single species of productid brachiopods, stromatoporoids, microconchids and cornulitids. The coral-associated macrobenthos has similarly a low diversity, being represented by single species of spiriferid and rhynchonellid brachiopods, and gastropods. Being developed in an offshore carbonate sedimentary system devoid of any organic-rich deposits, and characterized by extremely low abundance and diversity of suspension-feeding organisms, the biostrome is considered to have originated in a low productivity, oligotrophic environment strictly dominated by heterozoan coral communities. Its development in a well-oxygenated, oligotrophic environment during the time when organic-rich, black Kellwasser facies developed elsewhere, additionally attests for multi-causal scenarios for the Frasnian–Famennian event, during which other factors were responsible in different paleogeographic and facies settings. [ABSTRACT FROM AUTHOR]

Abstract: Significant differences between faunal and floral associations existing in different paleogeographic realms in the Kungurian–Late Permian interval make it difficult to correlate the Permian deposits of the world. Resolving this problem is one of the main tasks of Permian stratigraphy. The global significance of Permian strata of the Primorye region of Far East Russia is enhanced by the specific Middle Permian mixed Tethyan, Boreal and Gondwanan-type brachiopod fauna, mixed Angara-Euromerican-Cathaysian flora, and their close spatial and stratigraphical association with fusulinids, bryozoans, ammonoids, conodonts. These facts permit tracing of global correlational levels of some Permian sequences within the different paleobiogeographical realms: for example, the Monodiexodina sutschanica-Metadoliolina dutkevichi fusulinid zone of the Wordian age and Parafusulina stricta fusulinid zone of the Capitanian age. The Late Permian fauna of the Primorye is mainly Tethyan in origin and provides correlation with similar aged sequences from South China. [Copyright &y& Elsevier]

The evolutionary processes of speciation during the Cambrian radiation and their potential extrinsic drivers, such as episodic oceanic oxygenation events, remain unconfirmed. High-resolution temporal and spatial distribution of reef-associated archaeocyath sponge species on the Siberian Craton during the early Cambrian [ca. 528 to 510 million years ago] shows that speciation was driven by increased endemism particularly ca. 521 million years (59.7% endemic species) and 514.5 million years (65.25% endemic species) ago. These mark rapid speciation events after dispersal of ancestors from the Aldan-Lena center of origin to other regions. These speciation events coincided with major sea-level lowstands, which we hypothesize were intervals when relative deepening of the shallow redoxcline permitted extensive oxygenation of shallow waters over the entire craton. This provided oxic corridors for dispersal and allowed the formation of new founder communities. Thus, shallow marine oxygen expansion driven by sea-level oscillations provides an evolutionary driver for sucessive speciation events during the Cambrian radiation.

Oxygenation during the Cambrian Radiation progressed via a series of short-lived pulses. However, the metazoan biotic response to this episodic oxygenation has not been quantified, nor have the causal evolutionary processes been constrained. Here we present ecological analyses of Cambrian archaeocyath sponge reef communities on the Siberian Platform (525-514 Ma). During the oxic pulse at ~521-519 Ma, we quantify reef habitat expansion coupled to an increase in reef size and metacommunity complexity, from individual within-community reactions to their local environment, to ecologically complex synchronous community-wide response, accompanied by an increase in rates of origination. Subsequently, reef and archaeocyath body size are reduced in association with increased rates of extinction due to inferred expanded marine anoxia (~519-516.5 Ma). A later oxic pulse at ~515 Ma shows further reef habitat expansion, increased archaeocyath body size and diversity, but weaker community-wide environmental responses. These metrics confirm that oxygenation events created temporary pulses of evolutionary diversification and enhanced ecosystem complexity, potentially via the expansion of habitable space, and increased archaeocyath individual and reef longevity in turn leading to niche differentiation. Most notably, we show that progression towards increasing biodiversity and ecosystem complexity was episodic and discontinuous, rather than linear, during the Cambrian Radiation., (© 2022. The Author(s).)