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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]

Sponges are among the most common and diverse Cambrian fossils. However, the origin of the crown groups of the extant sponge classes constitutes the principal problem in the understanding of the evolution of these lower metazoans. New intact spiculate sponges from the lower Cambrian Stage 3–Stage 4 Sinsk Lagerstätte of the Siberian Platform enable a better understanding of the early evolution of crown‐group demosponges. The skeletons of Neomenispongia plexa and N. diazoma gen. et sp. nov. consist mostly of simple oxeas, which are organized in relatively regular tufts that are additionally strengthened by sigmoidal spicules. The C‐shaped elements of N. diazoma are megascleres in their size range but have sigmoidal shapes similar to sigma microscleres of extant demosponges; the sigmoidal spicules of N. plexa fully accord with microscleres and are the smallest spicules in known Cambrian demosponges. Together with an unnamed early Cambrian demosponge from the Sirius Passet biota (Greenland) and middle Cambrian Ulospongiella from the Burgess Shale (Canada), the new species represent the earliest heteroscleromorph demosponges and indicate an evolutionary origin of microscleres from megascleres. The thin, homogenous skeleton of Keithospongos loricatus gen. et sp. nov. is built of small, spirally arranged oxeas corresponding to the skeletal structure of the primitive Hazeliidae, which have been interpreted as the ancestral skeletal organization of demosponges. These new sponges therefore provide a link from extant spiculate demosponge groups to their more familiar Cambrian ancestors. [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]

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. During the Cambrian Radiation, oxygenation occurred in a series of short pulses. Here, the authors quantify episodic changes in reef size, extent of habitat and in metacommunity ecological complexity associated with these oxygenation pulses by examining archaeocyath sponges. [ABSTRACT FROM AUTHOR]

A multiscale computational scheme is proposed for ion dynamics that allows modeling based on primary information—data on the chemical composition of the material and its crystal structure. The scheme includes quantum mechanical and molecular dynamics modeling as well as Monte Carlo simulation of ion and electron dynamics taking into account the real crystal structure. Approbation of the proposed approach is carried out on a silicon oxide memristive element. The results of computational experiments are presented that demonstrate the stages of growth and destruction of a conductive filament under the action of a time‐varying voltage. [ABSTRACT FROM AUTHOR]

The sclerotized jaw elements (scolecodonts) of polychaete annelids are rarely preserved as articulated jaw apparatuses. Here we describe a morphologically unusual, rather large, and symmetrical jaw apparatus, assigned to the new taxon Boreognathus pogorevichi gen. et sp. nov., from the Kungurian (lower Permian) of the Pechora Coal Basin, northern Cis‐Urals, Russia. Whereas the specimen is mainly preserved as a three‐dimensional external mould of the near‐complete dorsal maxillary apparatus, some organic matter comprising the original jaw wall is also retained. The new taxon combines edentate, pincer‐like first maxillae (MI) typical of the extant Labidognatha apparatus type with long slender carriers common in the Prionognatha type. Unlike the smooth MI, MII are consistently and prominently denticulated. The new genus represents a hitherto unknown type of polychaete jaw apparatus and is assigned to the Palaeozoic family Atraktoprionidae. [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]

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 δ13C 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]

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]

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]

A novel experimental optical method, based on photoluminescence and photo-induced resonant reflection techniques, is used to investigate the spin transport over long distances in a new, recently discovered collective state—magnetofermionic condensate. The given Bose–Einstein condensate exists in a purely fermionic system (ν = 2 quantum Hall insulator) due to the presence of a non-equilibrium ensemble of spin-triplet magnetoexcitons—composite bosons. It is found that the condensate can spread over macroscopically long distances of approximately 200 μm. The propagation velocity of long-lived spin excitations is measured to be 25 m/s. [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]

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]

In modern microwave personnel screening systems, a 2-D synthetic aperture is used to obtain a radar image with resolution limited by the diffraction of electromagnetic waves. Therefore, the antenna system of the screening system has large dimensions, a large number of switched channels, and a high cost, which limits a wider use of these systems, for example, at ground transport hubs or administrative buildings. In this article, we consider a different method of forming synthetic aperture, in which it is formed due to the relative movement of a subject near a stationary antenna system. Using the described experimental setup and imitation experiment with a mannequin, it was shown that the proposed method can significantly reduce the dimensions of a prospective screening system and the number of channels in the antenna system and at the same time obtain detailed radar images of hidden objects. [ABSTRACT FROM AUTHOR]

Details of the Early-Middle Frasnian boundary interval of the Pymvashor River section (Timan-Pechora Basin, Cis-Urals, in the far north of European Russia) are revealed by biostratigraphically constrained carbonate (d13Ccarb) and organic carbon (d13Corg) stable data. The studied interval corresponds to the lower part of the Domanik Formation, which consists of interbedded limestone and shale beds. Organic-rich black shale that lacks bioturbation and benthic organisms indicates an oxygen-depleted depositional environment. Detection of isorenieratene derivatives in organic matter indicates that anoxia was present in the photic zone during deposition. The Pymvashor River section contains d13Ccarb and d13Corg isotope records related to the Early-Middle Frasnian isotope Event. The similarity between the Cis-Uralian (this study) and the Chinese d13Ccarb and d13Corg oscillations, including the twostep pattern of the recorded major positive excursions, suggests a robust correlation of the Late Devonian Early-Middle Frasnian isotope Event and minor intra-event excursions. Magnitude of variations and values of d13Corg and d13Ccarb in the punctata Zone in the Pymvashor River section are minor than those observed in the North American, Polish, and Chinese successions. Such difference may reflect specific variation of the local environments. [ABSTRACT FROM AUTHOR]

There is high similarity in sedimentation and taxonomic composition and stratigraphic succession of conodonts and brachiopods across the Frasnian-Famennian (F-F) transition in low- and mid-latitude realms of NE Laurussia and Siberia. This uniformity suggests the presence of low environmental gradients between 10° S and 40° N of the northern hemisphere corresponding to tropical and subtropical climatic zones. The changes in taxonomic diversity in these marine faunas occurred gradually throughout the Frasnian, and were paired with similar, mostly carbonate facies settings, marked by rare development of the Kellwasser-type organic-rich deposits. Moderated ecological effect of the rapid climatic shifts during the F-F crisis is also noteworthy, especially for the shelly benthos, with an exception of the Lilliput effect. [ABSTRACT FROM AUTHOR]

Many aspects of the drivers for, and evolutionary dynamics of, the Cambrian Explosion are poorly understood. Here we quantify high-resolution changes in species body size in major metazoan groups on the Siberian Platform during the early Cambrian (ca. 540–510 Million years ago (Ma)). Archaeocyath sponges, hyolith lophophorates, and helcionelloid mollusc species show dynamic and synchronous trends over million-year timescales, with peaks in body size during the latest Tommotian/early Atbadanian and late Atdabanian/early Botoman, and notably small body sizes in the middle Atdabanian and after the Sinsk anoxic extinction event, starting ca. 513 Ma. These intervals of body size changes are also mirrored in individual species and correlate positively with increased rates of origination and broadly with total species diversity. Calcitic brachiopods (rhynchonelliformeans), however, show a general increase in body size following the increase in species diversity through this interval: phosphatic brachiopods (linguliformeans) show a body size decrease that negatively correlates with diversity. Both brachiopod groups show a rapid recovery at the Sinsk Event. The synchronous changes in these metrics in archaeocyath, hyoliths and helcionelloids suggest the operation of external drivers through the early Cambrian, such as episodic changes in oxygenation or productivity. But the trends shown by brachiopods suggests a differing physiological response. Together, these dynamics created both the distinct evolutionary record of metazoan groups during the Cambrian Explosion and determined the nature of its termination. [ABSTRACT FROM AUTHOR]

Oligochaetes, despite their important role in terrestrial ecosystems and a tremendous biomass, are extremely rare fossils. The palaeontological record of these worms is restricted to some cocoons, presumable trace fossils and a few body fossils the most convincing of which are discovered in Mesozoic and Cenozoic strata. The Olenekian (Lower Triassic) siliciclastic lacustrine Petropavlovka Lagerstätte of the southern Cis-Urals yields a number of extraordinary freshwater fossils including an annelid. The segmented body with a secondary annulation of this fossil, a subtriangular prostomium, a relatively thick layered body wall and, possibly, the presence of a genital region point to its oligochaete affinities. Other fossil worms which have been ascribed to clitellates are reviewed and, with a tentative exception of two Pennsylvanian finds, affinities of any pre-Mesozoic forms to clitellate annelids are rejected. The new fossil worm allows tracing of a persuasive oligochaete record to the lowermost Mesozoic and confirms a plausibility of the origin of this annelid group in freshwater conditions. [ABSTRACT FROM AUTHOR]

Diverse skeletal assemblage has been discovered in the Ediacaran/Cambrian strata of the Codos locality in NE Spain (Aragón, Cadenas Ibéricas). This assemblage includes at least seven genera, only three of which can be ascribed to known taxa. All the fossils are preserved in phosphate but their original microstructures are traceable by both elementary composition and microstructural features that are indicative for primary aragonite and high-magnesium calcite biomineralogies. Already these early skeletal fossils show sophisticated microstructures represented by heterogeneous multilayered composites to satisfy the requirements for better protection against both chemical dissolution and mechanical predator deterioration. The most common and best-preserved fossil, which is tubicolous Codositubulus grioensis gen. et sp. nov., is described here. The composition of the fossil assemblage and its stratigraphic position are indicative for the lowermost Terreneuvian (lower Cambrian) or even pre-Terreneuvian age of this fauna. [ABSTRACT FROM AUTHOR]

Copyright of FME Transactions is the property of University of Belgrade, Faculty of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Estonian Journal of Earth Sciences is the property of Teaduste Akadeemia Kirjastus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new taxonomical evaluation of the rostrum symmetry and its ontogenetic changes in advanced species of Siphonodella on the basis of collections from the Polar and Subpolar Urals, Chernyshev and Pechora ridges, Russia, is presented. Morphology of dextral and sinistral P1 elements of advanced Siphonodella was studied with SEM, optical microscopy, and X-ray microtomography. The investigations demonstrate that the rostrum, appearing at early stages of ontogeny, promises to be a useful trait for taxonomy and discrimination of the juvenile forms. The changes in the rostrum symmetry and ornamentation of P1 elements during the evolution of Siphonodella are considered as the major morphological events. The significant diversification of the genus in the Late duplicata-crenulata zones coincides with the appearance of the new rostrum structures. The nearly synchronous increase in complexity of the rostrum suggests that all the advanced Siphonodella species possessed a common ancestor. Three new species are described: Siphonodella ludmilae, S. lanei, and S. gladia. [ABSTRACT FROM AUTHOR]

Copyright of Estonian Journal of Earth Sciences is the property of Teaduste Akadeemia Kirjastus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Conodonts are an extinct group of marine animals possessing debated affinities. The conodont elements are composed of calcium phosphate [apatite (CaF)] and collagen-like proteins. Distribution of Sr in the bioapatite of albid, lamellar and paralamellar tissues of some Upper Devonian conodont element crowns from NW Russia was studied by microprobe. The calcium phosphate of the lamellar and paralamellar tissues demonstrates periodical oscillation of Sr contents across the lamellae (0.4-0.5 wt% in the outer part of lamella, and 0.2 wt% in the inner part). The albid tissue contains Sr of less than 0.4 wt%. It is suggested that oscillations of Sr concentrations reflect the periodic growth of the lamellae, and the average Ca/Sr ratio can be a proxy of the growth rate. [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]

Detailed analysis of the distribution of archaeocyaths in five lower Cambrian sections in South China has resulted in the erection of four new archaeocyathan zones and one new archaeocyathan bed. Listed in order of ascending age, these are: the Dailycyathus xiuqiensis Zone; the Dictyocyathus shaanxiensis Zone; the Spirillicyathus duplex Range Zone; the Sibirecyathus meitanensis Range Zone; and the Archaeocyathus yanjiaoensis beds. These new subdivisions permit a correlation of lower Cambrian strata both within the area of the Yangtze Platform (South China) as well as between this region and Siberia, Australia, Western Europe and North America. Within the Yangtze Platform area, archaeocyaths of the Dailycyathus xiuqiensis and Dictyocyathus shaanxiensis zones co-occur with trilobites of the middle and upper Eoredlichia Trilobite Zone of the Qiongzhusian Stage. The Spirillicyathus duplex and the Sibirecyathus meitanensis Range Zone correspond to the Malungia, Yiliangella–Yunnanaspis and Drepanuroides Trilobite zones of the basal and middle Canglangpuan Stage, respectively. Finally, the Archaeocyathus yanjiaoensis beds belong to the Palaeolenus fengyangensis Trilobite Zone of the upper Canglangpuan Stage. Global correlations based on archaeocyath assemblage zones suggest that: (1) the middle–upper Qiongzhusian of South China correlates with the middle Atdabanian Stage of the Siberian Platform, the Warriootacyathus wilkawillinensis Archaeocyath Zone in South Australia, the middle Issendalenian Stage of Morocco and the lower Ovetian Stage in Spain; (2) the lowermost Canglangpuan Stage of South China correlates with the uppermost Atdabanian of the Siberian Platform, the Spirillicyathus tenuis – Jugalicyathus tardus archaeocyath zones in South Australia, the uppermost Issendalenian – lower Banian stages of Morocco, the middle Ovetian Stage of Spain and the middle Montezuman Stage of North America; (3) the middle Canglangpuan Stage approximates the lowermost Botoman Stage of the Siberian Platform, middle Banian Stage of Morocco, the uppermost Ovetian – lowermost Marianian stages of Spain and the upper Montezuman Stage of North America; (4) the uppermost Canglangpuan Stage is equivalent of the middle Toyonian Stage of the Siberian Platform, Archaeocyathus abacus beds in Australia, the middle Bilbilian Stage in Spain and the middle Dyeran Stage (Bolbolenellus euryparia Trilobite Zone) in North America. [ABSTRACT FROM AUTHOR]

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]

A current paradigm accepts the presence of weakly biomineralized animals only, barely above a low metazoan grade of organization in the terminal Neoproterozoic (Ediacaran), and a later, early Cambrian burst of well skeletonized animals. Here we report new assemblages of primarily calcareous shelly fossils from upper Ediacaran (553-542 Ma) carbonates of Spain and Russia (Siberian Platform). The problematic organism Cloudina is found in the Yudoma Group of the southeastern Siberian Platform and different skeletal taxa have been discovered in the terminal Neoproterozoic of several provinces of Spain. New data on the morphology and microstructure of Ediacaran skeletal fossils Cloudina and Namacalathus indicate that the Neoproterozoic skeletal organisms were already reasonably advanced. In total, at least 15 skeletal metazoan genera are recorded worldwide within this interval. This number is comparable with that known for the basal early Cambrian. These data reveal that the terminal Neoproterozoic skeletal bloom was a real precursor of the Cambrian radiation. Cloudina, the oldest animal with a mineralised skeleton on the Siberian Platform, characterises the uppermost Ediacaran strata of the Ust'-Yudoma Formation. While in Siberia Cloudina co-occurs with small skeletal fossils of Cambrian aspect, in Spain Cloudina-bearing carbonates and other Ediacaran skeletal fossils alternate with strata containing rich terminal Neoproterozoic trace fossil assemblages. These finds treated together provide a possibility to correlate transitional Neoproterozoiclower Cambrian strata around the world. Such a correlation concurs with available isotope and radiometric data and indicates that typical Ediacaran shelly fossils have not crossed the Precambrian-Cambrian boundary. [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]

We describe the first occurrence of the problematic fossil Gaojiashania outside China, in the Ediacaran Yudoma Group of the Siberian Platform. In both areas, Gaojiashania characterizes the lower upper Ediacaran strata and precedes the appearance of Cloudina and other skeletal fossils, which highlights its significance for the Ediacaran subdivision and correlation. Features of this fossil such as indeterminate length, the absence of a distinct growth pattern, and selfavoiding behaviour indicate its trace fossil origin but do not necessarily imply metazoan affinities for its producers. Several organisms including stem-group social amoebozoans and unicellular protistsmay have been Proterozoic trace fossil producers. [ABSTRACT FROM AUTHOR]

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The elements of many conodont taxa exhibit a polygonal surface micro-ornamentation. Four main types are recognized (striation, linear texture, regular (idiomorphic) texture and granular texture) and their distribution over the conodont elements of different morphology is considered. The intraspecific (ontogenetic and ecological) and interspecific (phylogenetic) causes of the reticulation texture variations are also considered. [ABSTRACT FROM AUTHOR]

Reefal buildups in western Mongolia of mid-Early Cambrian (late Atdabanian) age flourished during a period when shelf seas were globally widespread. The succession at Zuune Arts records the transition from shallow marine siliciclastic sediments (Bayan Gol Formation) to shallow marine, but still clastic-influenced, carbonates (Salaany Gol Formation). The Salaany Gol Formation is interpreted as having been deposited as a series of shallowing upwards cycles on a shallow, gently inclined shelf in a rapidly subsiding epicontinental sea. Cycles commenced with the growth of subtidal metazoan-calcimicrobe aggregative communities on an open shelf. The resultant buildups were commonly engulfed by extensive, massive microbial stromatolites when they grew in agitated intertidal conditions. Latterly, they were smothered by ooids shoals in response to rapid sea level rise. Four types of reefal buildup are distinguished: (1) green-coloured calcimicrobe (Tarthinia, Epiphyton, Gordonophyton and Renalcis) boundstones; (2) red-or green-coloured Cambrocyathellus-Tarthinia-Epiphyton bafflestones; (3) red-coloured Okulithchicyathus bindstones; and (4) red-coloured radiocyath-archaeocyath-cribricyath bioherms. Each is interpreted as having grown at increasing depths and possibly sedimentation rates. The buildups are commonly enclosed within graded and planar bedded bioclastic grainstones and packstones, and are best developed towards the top of the formation, when sea level was high. Thickets of large, solitary archaeocyaths are also inferred in the deeper interbiohermal areas. These buildups had synoptic relief and constructed porous structures with growth-framework cavities housing diverse coelobiontic communities. Extensive synoptic relief and constructed porous structures with growth-framework cavities housing diverse coelobiontic communities. Extensive synsedimentary cements are present, including pseudomorphed aragonitic fans and possible pseudomorphed aragontic botryoids.... [ABSTRACT FROM AUTHOR]