Institute of Paleontology A A Borisyak

Phylogenies are usually dated by calibrating interior nodes against the fossil record. This relies on indirect methods that, in the worst case, misrepresent the fossil information. Here, we contrast such node dating with an approach that includes fossils along with the extant taxa in a Bayesian total-evidence analysis. As a test case, we focus on the early radiation of the Hymenoptera, mostly documented by poorly preserved impression fossils that are difficult to place phylogenetically. Specifically, we compare node dating using nine calibration points derived from the fossil record with total-evidence dating based on 343 morphological characters scored for 45 fossil (4--20 complete) and 68 extant taxa. In both cases we use molecular data from seven markers (∼5 kb) for the extant taxa. Because it is difficult to model speciation, extinction, sampling, and fossil preservation realistically, we develop a simple uniform prior for clock trees with fossils, and we use relaxed clock models to accommodate rate variation across the tree. Despite considerable uncertainty in the placement of most fossils, we find that they contribute significantly to the estimation of divergence times in the total-evidence analysis. In particular, the posterior distributions on divergence times are less sensitive to prior assumptions and tend to be more precise than in node dating. The total-evidence analysis also shows that four of the seven Hymenoptera calibration points used in node dating are likely to be based on erroneous or doubtful assumptions about the fossil placement. With respect to the early radiation of Hymenoptera, our results suggest that the crown group dates back to the Carboniferous, ∼309 Ma (95% interval: 291--347 Ma), and diversified into major extant lineages much earlier than previously thought, well before the Triassic. [Bayesian inference; fossil dating; morphological evolution; relaxed clock; statistical phylogenetics.].

Here, palaeobotanical and genetic data for common beech (Fagus sylvatica) in Europe are used to evaluate the genetic consequences of long-term survival in refuge areas and postglacial spread. Four large datasets are presented, including over 400 fossil-pollen sites, 80 plant-macrofossil sites, and 450 and 600 modern beech populations for chloroplast and nuclear markers, respectively. The largely complementary palaeobotanical and genetic data indicate that: (i) beech survived the last glacial period in multiple refuge areas; (ii) the central European refugia were separated from the Mediterranean refugia; (iii) the Mediterranean refuges did not contribute to the colonization of central and northern Europe; (iv) some populations expanded considerably during the postglacial period, while others experienced only a limited expansion; (v) the mountain chains were not geographical barriers for beech but rather facilitated its diffusion; and (vi) the modern genetic diversity was shaped over multiple glacial-interglacial cycles. This scenario differs from many recent treatments of tree phylogeography in Europe that largely focus on the last ice age and the postglacial period to interpret genetic structure and argue that the southern peninsulas (Iberian, Italian and Balkan) were the main source areas for trees in central and northern Europe.

2,604 names at the rank of subtribe, tribe, subfamily, family and superfamily have been proposed for Recent and fossil gastropods, and another 35 for monoplacophorans. All names are listed in a nomenclator giving full bibliographical reference, date of publication, typification, and their nomenclatural availability and validity under the International Code of Zoological Nomenclature. Another 790 names, established for categories above the familygroup (infraorder to subclass) are listed separately. A fully ranked, hierarchical classification summarizes recent advances in the phylogeny of the Gastropoda and Monoplacophora. In all, the classification recognizes as valid a total of 721 gastropod families, of which 245 are known exclusively as fossils and 476 occur in the Recent with or without a fossil record; and 20 monoplacophoran families, of which 1 only occurs as Recent.Nomenclatural acts in this work: Amberleya bathonica Cox & Arkell, 1950, fixed as type species of Amberleya J. Morris & Lycett, 1851, under Art. 70.3; Ampezzopleura tenuis Nützel, 1998, fixed as type species of Ampezzopleura Bandel, 1991, under Art. 70.3; Proserpina nitida G. B. Sowerby II, 1839, designated type species of Despoena Newton, 1891; Buccinum glabratum Linnaeus, 1758, designated type species of Dipsaccus H. Adams & A. Adams, 1853; Murex ficus Linnaeus, 1758, designated type species of Ficula Swainson, 1835; Oncomelania hupensis Gredler, 1881, designated type species of Hemibia Heude, 1890; Murex metaxa Delle Chiaje, 1828, fixed as type species of Metaxia Monterosato, 1884 under Art. 70.3; Neridomus anglicus Cox & Arkell, 1950, fixed as type species of Neridomus J. Morris & Lycett, 1851, under Art. 70.3; Navicella clypeolum Récluz, 1843, designated type species of Orthopoma Gray, 1868; Trochus viadrinus M. Schmidt, 1905, fixed as type species of Parataphrus Chavan, 1954 under Art. 70.3; Helix pomatia Linnaeus, 1758, designated type species of Pentataenia A. Schmidt, 1855; Flammulina ponsonbyi Suter, 1897, fixed as type species of Phenacohelix Suter, 1892, under Art. 70.3; Cyrtolites corniculum Eichwald, 1860, fixed as type species of Pollicina Koken, 1895, under Art. 70.3; Purpurina elegantula d'Orbigny, 1850, designated as type species of Purpurina d'Orbigny, 1850, and lectotype of Turbo bellona d'Orbigny, 1850, designated as neotype of Purpurina elegantula; Pyramidella minuscula Monterosato, 1880, fixed as type species of Tiberia Jeffreys, 1884, under Art. 70.3; Cyclostoma delicatum Philippi, 1844, fixed as type species of Trachysma G. O. Sars, 1878, under Art. 70.3; Helix elegans Gmelin, 1791, fixed as type species of Trochoidea T. Brown, 1827, under Art. 70.3; Turritellopsis stimpsoni Dall, 1919, fixed as type species of Turritellopsis G. O. Sars, 1878, under Art. 70.3; Fusus averillii Gabb, 1864, fixed as type species of Volutoderma Gabb, 1876, under Art. 70.3; Voluta pepo Lightfoot, 1786, fixed as type species of Yetus Bowdich, 1822. Curnonidae d'Udekem d'Acoz, nom. nov., and Curnon d'Udekem d'Acoz, nom. nov., are established for Charcotiidae Odhner, 1926, and Charcotia Vayssière, 1906, (between 27 March and 1 May), non Charcotia Chevreux, 1906 (January) [Amphipoda]; Yuopisthonematidae Nützel, nom. nov., and Yuopisthonema Nützel, nom. nov., are established for Opisthonematidae Yu, 1976, and Opisthonema Yu, 1974, non Gill, 1862 [Pisces]. The new family-group name Burnupiidae Albrecht is established in this work; and the names Scolodontina and Orthalicoidei are first used here to denote, respectively, a suborder containing the family Scolodontidae, and an infraorder containing the superfamily Orthalicoidea.

The order Coleoptera (beetles) is arguably the most speciose group of animals, but the evolutionary history of beetles, including the impacts of plant feeding (herbivory) on beetle diversification, remain poorly understood. We inferred the phylogeny of beetles using 4,818 genes for 146 species, estimated timing and rates of beetle diversification using 89 genes for 521 species representing all major lineages and traced the evolution of beetle genes enabling symbiont-independent digestion of lignocellulose using 154 genomes or transcriptomes. Phylogenomic analyses of these uniquely comprehensive datasets resolved previously controversial beetle relationships, dated the origin of Coleoptera to the Carboniferous, and supported the codiversification of beetles and angiosperms. Moreover, plant cell wall-degrading enzymes (PCWDEs) obtained from bacteria and fungi via horizontal gene transfers may have been key to the Mesozoic diversification of herbivorous beetles-remarkably, both major independent origins of specialized herbivory in beetles coincide with the first appearances of an arsenal of PCWDEs encoded in their genomes. Furthermore, corresponding (Jurassic) diversification rate increases suggest that these novel genes triggered adaptive radiations that resulted in nearly half of all living beetle species. We propose that PCWDEs enabled efficient digestion of plant tissues, including lignocellulose in cell walls, facilitating the evolution of uniquely specialized plant-feeding habits, such as leaf mining and stem and wood boring. Beetle diversity thus appears to have resulted from multiple factors, including low extinction rates over a long evolutionary history, codiversification with angiosperms, and adaptive radiations of specialized herbivorous beetles following convergent horizontal transfers of microbial genes encoding PCWDEs.

A uranium-lead zircon age for a volcanic ash interstratified with fossil-bearing, shallow marine siliciclastic rocks in the Zimnie Gory section of the White Sea region indicates that a diverse assemblage of body and trace fossils occurred before 555.3 +/- 0.3 million years ago. This age is a minimum for the oldest well-documented triploblastic bilaterian Kimberella. It also makes co-occurring trace fossils the oldest that are reliably dated. This determination of age implies that there is no simple relation between Ediacaran diversity and the carbon isotopic composition of Neoproterozoic seawater.

(1988). An Outline of Evolution of the Hymenopterous Insects (Order Vespida) Oriental Insects: Vol. 22, No. 1, pp. 115-145.

Functional, constructional, and preservational criteria led to a reinterpretation of seemingly complex trace fossils and the majority of assumed metazoan body fossils from Vendian lagerstatten. In the new scenario, Ediacaran biota were dominated by procaryote biomats and giant protozoa (Xenophyophoria and Vendobionta), which developed a great variety of shapes and lifestyles in the climatically controlled “golden age” that followed the Marinoan snowball earth. Contemporary metazoans (sponges; polyps; soft-bodied mollusks; possible echinoderms; worm-like burrowers) were adapted to this non-uniformitarian environment, but they remained scarce and relatively small. Some phyla (arthropods, brachiopods) appear to have still been absent. Our study also accentuates the Cambrian Explosion, which put an end to the peaceful “Garden of Ediacara”. Not only did the former rulers become extinct or restricted to less favorable environments, but the radiation of metazoan phyla was also accompanied by an ecological revolution that established a new and more dangerous world, which persists to the present day.

Aim To understand the impact of glacial refugia and migration pathways on the modern genetic diversity of Pinus sylvestris. Location The study was carried out throughout Europe. Methods An extended set of data of pollen and macrofossil remains was used to locate the glacial refugia and reconstruct the migrating routes of P. sylvestris throughout Europe. A vegetation model was used to simulate the extent of the potential refugia during the last glacial period. At the same time a genetic survey was carried out on this species. Results The simulated distribution of P. sylvestris during the last glacial period is coherent with the observed fossil data, which showed a patchy distribution of the refugia between c . 40°N and 50°N. Several migrational fronts were detected within the Iberian and the Italian peninsulas, and outside the Hungarian plain and around the Alps. The modern mitochondrial DNA depicted three different haplotypes for P. sylvestris. Two distinct haplotypes were restricted to northern Spain and Italy, and the third haplotype dominated most of the present-day remaining distribution range of P. sylvestris in Europe. Main conclusions During the last glacial period P. sylvestris was constrained under severe climatic conditions to survive in scattered and restricted refugial areas. Combining palaeoenvironmental data, vegetation modelling and the genetic data, we have shown that the long-term isolation in the glacial refugia and the migrational process during the Holocene have played a major role in shaping the modern genetic diversity of P. sylvestris in Europe.

The head and mouthpart structures of 11 species of Eurasian scorpionflies represent three extinct and closely related families during a 62-million-year interval from the late Middle Jurassic to the late Early Cretaceous. These taxa had elongate, siphonate (tubular) proboscides and fed on ovular secretions of extinct gymnosperms. Five potential ovulate host-plant taxa co-occur with these insects: a seed fern, conifer, ginkgoopsid, pentoxylalean, and gnetalean. The presence of scorpionfly taxa suggests that siphonate proboscides fed on gymnosperm pollination drops and likely engaged in pollination mutualisms with gymnosperms during the mid-Mesozoic, long before the similar and independent coevolution of nectar-feeding flies, moths, and beetles on angiosperms. All three scorpionfly families became extinct during the later Early Cretaceous, coincident with global gymnosperm-to-angiosperm turnover.

Confirming the identity of early animals The first complex organisms emerged during the Ediacaran period, around 600 million years ago. The taxonomic affiliation of many of these organisms has been difficult to discern. Fossils of Dickinsonia , bilaterally symmetrical oval organisms, have been particularly difficult to classify. Bobrovskiy et al. conducted an analysis using lipid biomarkers obtained from Dickinsonia fossils and found that the fossils contained almost exclusively cholesteroids, a marker found only in animals (see the Perspective by Summons and Erwin). Thus, Dickinsonia were basal animals. This supports the idea that the Ediacaran biota may have been a precursor to the explosion of animal forms later observed in the Cambrian, about 500 million years ago. Science , this issue p. 1246 ; see also p. 1198

Origin of the eukaryotic organisms (including the multicellular animals or Metazoa) is commonly considered to be related to growing oxygen content in the atmosphere up to a level that allows aerobic metabolism. Here it is suggested that oxygenation of the biosphere was not a permissive condition but rather a forcing factor that drove evolution towards the formation of complex biological systems. Growing concentration of free oxygen in conjunction with other geohistorical trends acted to chemically impoverish the ocean and atmosphere and made many of the chemical elements immobile or unavailable for metabolic processes. Of particular importance in this connection was the decreasing concentration in sea water of the heavy metals that demonstrate high catalytic ability and make an active center in many enzymes. Increasing biological complexity and the eukaryotization of the biosphere (origin of the eukaryotic cell, growing role of heterotrophy, increasing biodiversity, rise of multicellular organisms, lengthening of trophic chains, acceleration of biological recycling of the chemical elements, etc.) can be considered as an evolutionary response to the geochemical deterioration of the environment.Recent discoveries of the oldest megascopic eukaryotes, such as spiral Grypania (1.9 Ga), the necklace-like colonial organism of tissue-grade organization Horodyskia (1.5 Ga), vermiform Parmia (about 1.0 Ga) and Sinosabellidites (800 Ma ago) are consisitent with the "molecular clock" models on an early origin of animals; metazoans were, however, confined to relatively cold and well oxygenated basins beyond the carbonate belt of the ocean until the end of the Proterozoic. Large and diverse invertebrates of the Vendian Period are known mostly from siliciclastic marine basins. This fauna is characterized by high density of the benthic populations and well established clades both at the diploblastic (e.g., Phylum Trilobozoa) and triploblastic (e.g., Phylum Proarticulata) grades of organization as well as some taxa related to the Paleozoic phyla. An organic skeleton preceded the rise of the mineralized skeleton in some metazoan phyla. Low temperature of the habitats inhibited biomineralization. Almost simultaneous development of the phosphatic, carbonate and siliceous skeletons in different metazoan groups at the beginning of the Cambrian Period some 545 Ma ago could be related to the colonization of the warm carbonate basins by the metazoans. An additional factor for the rapid diversification of the biomineralized phyla could be the growing length of the trophic chains brought about by the rapidly increasing biodiversity and the need for detoxification at the top of the trophic pyramid. Being the byproduct of detoxification, sclerites and spicules, hard mineralized shells and carapaces immediately became an important factor of morphological evolution and growing biodiversity, as well as the object of intensive selection under the growing pressure of predators. Explosive growth of morphophysiological diversity in metazoans during the Vendian and Cambrian had an enormous impact on evolution of other groups of organisms and on the environment.

The archosaur species Teleocrater rhadinus, part of the new clade Aphanosauria, is an example of the earliest divergence of the avian stem lineage (Avemetatarsalia), the lineage that contains dinosaurs (including birds). The early history of the bird-line archosaurs, a group including dinosaurs, birds and pterosaurs, but excluding crocodilians, is not well defined. This is due in part to a fragmentary fossil record, but the distinctive morphology of pterosaurs has also obscured their ancestry. Sterling Nesbitt and colleagues describe a new species, Teleocraterrhadinus, from the Middle Triassic of Tanzania, that represents the most primitive known member of the bird-line archosaurs. Teleocrater provides the best guide so far to the ancestral bird-line condition. It was a lightly built, quadrupedal carnivore, so more like a crocodile than the small bipeds often depicted at this point in archosaur evolution. These are long-awaited findings on Teleocrater, which was undergoing study by the late Alan Charig of the Natural History Museum in London, and remained unpublished on his death in 1997. The relationship between dinosaurs and other reptiles is well established1,2,3,4, but the sequence of acquisition of dinosaurian features has been obscured by the scarcity of fossils with transitional morphologies. The closest extinct relatives of dinosaurs either have highly derived morphologies5,6,7 or are known from poorly preserved8,9 or incomplete material10,11. Here we describe one of the stratigraphically lowest and phylogenetically earliest members of the avian stem lineage (Avemetatarsalia), Teleocrater rhadinus gen. et sp. nov., from the Middle Triassic epoch. The anatomy of T. rhadinus provides key information that unites several enigmatic taxa from across Pangaea into a previously unrecognized clade, Aphanosauria. This clade is the sister taxon of Ornithodira (pterosaurs and birds) and shortens the ghost lineage inferred at the base of Avemetatarsalia. We demonstrate that several anatomical features long thought to characterize Dinosauria and dinosauriforms evolved much earlier, soon after the bird–crocodylian split, and that the earliest avemetatarsalians retained the crocodylian-like ankle morphology and hindlimb proportions of stem archosaurs and early pseudosuchians. Early avemetatarsalians were substantially more species-rich, widely geographically distributed and morphologically diverse than previously recognized. Moreover, several early dinosauromorphs that were previously used as models to understand dinosaur origins may represent specialized forms rather than the ancestral avemetatarsalian morphology.

Polyneoptera represents one of the major lineages of winged insects, comprising around 40,000 extant species in 10 traditional orders, including grasshoppers, roaches, and stoneflies. Many important aspects of polyneopteran evolution, such as their phylogenetic relationships, changes in their external appearance, their habitat preferences, and social behavior, are unresolved and are a major enigma in entomology. These ambiguities also have direct consequences for our understanding of the evolution of winged insects in general; for example, with respect to the ancestral habitats of adults and juveniles. We addressed these issues with a large-scale phylogenomic analysis and used the reconstructed phylogenetic relationships to trace the evolution of 112 characters associated with the external appearance and the lifestyle of winged insects. Our inferences suggest that the last common ancestors of Polyneoptera and of the winged insects were terrestrial throughout their lives, implying that wings did not evolve in an aquatic environment. The appearance of the first polyneopteran insect was mainly characterized by ancestral traits such as long segmented abdominal appendages and biting mouthparts held below the head capsule. This ancestor lived in association with the ground, which led to various specializations including hardened forewings and unique tarsal attachment structures. However, within Polyneoptera, several groups switched separately to a life on plants. In contrast to a previous hypothesis, we found that social behavior was not part of the polyneopteran ground plan. In other traits, such as the biting mouthparts, Polyneoptera shows a high degree of evolutionary conservatism unique among the major lineages of winged insects.

The skeleton undergoes substantial histological modification during ontogeny in association with longitudinal growth, shape changes, reproductive activity, and fatigue repair. This variation can hinder attempts to reconstruct life history attributes for individuals, particularly when only fossil materials are availble for study. Histological examinations of multiple elements throughout development provide a means to control for such variability and facilitate accurate life history assessments. In the present study, the microstructure of various major long bones of the ceratopsian Psittacosaurus monogoliensis Osborn were examined from a growth series spanning juvenile through adult developmental stages. The first reconstruction of a growth curve (mass vs. age) for a dinosaur was made for this taxon using a new method called Developmental Mass Extrapolation. The results suggest P. mongoliensis: (1) had an S-shaped growth curve characteristics of most extant vertebrates, and (2) had maximal growth rates that exceeded extant reptiles and marsupials, but were slower than most avian and eutherian taxa.

Recent focus on plant‐insect associations during the angiosperm radiation from the last 30 million years of the Early Cretaceous has inadvertently de‐emphasized a similar but earlier diversification that occurred among gymnosperms. The existence of gymnosperm‐insect associations during the preangiospermous Mesozoic is evidenced by mouthparts capable of reaching and imbibing pollination drops or similar fluids, availability of pollen types consistent with entomophily, and opportunities for related consumption of pollen, seeds, and reproductively associated tissues in major seed‐plant groups, namely seed ferns, conifers, cycads, bennettitaleans, and gnetaleans. Based on stereotypical plant damage, head‐adherent pollen, gut contents, wing structure, mouthpart morphology and insect damage to plant reproductive organs, the likely nectarivores, pollinivores and pollinators were orthopterans, phasmatodeans, webspinners, sawflies and wasps, moths, beetles, mecopteroids, and true flies. These associations are ranked from possible to probable although the last three insect clades provide the strongest evidence for pollinator activity. We document two mid Cretaceous examples of these associations—cycadeoideaceous bennettitaleans and beetles and a cheirolepidiaceous conifer and flies—for which there are multiple lines of evidence for insect consumption of plant reproductive tissues but also pollination mutualisms. These data highlight the independent origin of a major phase of plant‐insect pollinator‐related associations during the mid Mesozoic that served as a prelude for the separate, iterative and later colonization of angiosperms.

MIKHAILOV K. E.: Classification of fossil eggshells of amniotic vertebrates. Acta Palaeont. Polonica, 36, 2, 193-238. Fossil avian and reptilian eggs and eggshells, from the Cretaceous of Mongolia and USSR (Kazakhstan, Zaisan basin) as well as samples of dinosaurian and the Eocene avian eggshells from USA, China, France and Argentina were studied. Methodological, terminological and biomineralization aspects of eggshell structure are discussed. Considered are different classifications of eggshell according to the structural levels of eggshell matter organization (texture. general histostructure, superficial morphology). Basic types, morphotypes, types of pore system and types of surface ornamentation are the main structural categories employed in the systematic description of fossil material. About 18 groups of fossil eggshells referred to turtles, geckoes, crocodiles, and to 14 families or dinosaur and bird oological remains are described. Their composition, occurence, paleobiology and systematics are shortly presented.

Sea-level fluctuations in the terminal Eocene, Oligocene, and Neogene of the Eastern Paratethys are quantitatively assessed on the basis of facies and old coastlines traced on the northern platform shelf, levels of river valley incisions, and the study of seismic profiles. The first data massif allows the characterization and correlation of transgression stages in the history of the Eastern Paratethys. The greatest transgressions fall within the first half of the Late Eocene, mid-Early Oligocene, initial Late Oligocene, initial Early Miocene, the initial Tchokrakian, Karaganian and Sarmatian in the Middle Miocene, the middle and late Sarmatian and early Pontian in the Late Miocene, and the Akchagylian in the Caspian basin of the Pliocene. In contrast, the greatest incisions of northern rivers running from the platform allow us to establish the time and extent of the main declines in the base levels of the erosion. Maximal incisions date back to the terminal Eocene-initial Oligocene, terminal Solenovian time in the terminal Rupelian, the terminal Maikop in the Early Miocene, the terminal Sarmatian and middle Pontian in the Late Miocene, and the Early Pliocene in the Caspian basin. Large regressions also formed unconformity surfaces, traced on seismic profiles as erosion boundaries of several orders. The surfaces are confined to the Eocene/Oligocene boundary, middle and late Maikop, Sarmatian/Meotian boundary, middle Pontian, and terminal Miocene-initial Pliocene, as well as being traced even in the most deep-water basins. The synthesis of these data suggests a preliminary version for the curve of transgression-regression cyclicity. Its correlation with the eustatic curve shows their similarity only in the lower part-prior to the initial Middle Miocene, when Paratethys became a semi-closed basin.

Research Article| May 01, 1994 Multiple δ13C excursions spanning the Cambrian explosion to the Botomian crisis in Siberia M. D. Brasier; M. D. Brasier 1Department of Earth Sciences, Oxford University, Parks Road, Oxford OX1 3PR, United Kingdom Search for other works by this author on: GSW Google Scholar R. M. Corfield; R. M. Corfield 1Department of Earth Sciences, Oxford University, Parks Road, Oxford OX1 3PR, United Kingdom Search for other works by this author on: GSW Google Scholar L. A. Derry; L. A. Derry 2Centre Nationale de Recherches Scientifiques, Centre de Recherches Pétrographiques et Géochemiques, 54501 Vandoeuvre-les-Nancy, France Search for other works by this author on: GSW Google Scholar A. Yu. Rozanov; A. Yu. Rozanov 3Palaeontological Institute, 113 Profsoyuznaya, Moscow 117647, Russia Search for other works by this author on: GSW Google Scholar A. Yu. Zhuravlev A. Yu. Zhuravlev 3Palaeontological Institute, 113 Profsoyuznaya, Moscow 117647, Russia Search for other works by this author on: GSW Google Scholar Author and Article Information M. D. Brasier 1Department of Earth Sciences, Oxford University, Parks Road, Oxford OX1 3PR, United Kingdom R. M. Corfield 1Department of Earth Sciences, Oxford University, Parks Road, Oxford OX1 3PR, United Kingdom L. A. Derry 2Centre Nationale de Recherches Scientifiques, Centre de Recherches Pétrographiques et Géochemiques, 54501 Vandoeuvre-les-Nancy, France A. Yu. Rozanov 3Palaeontological Institute, 113 Profsoyuznaya, Moscow 117647, Russia A. Yu. Zhuravlev 3Palaeontological Institute, 113 Profsoyuznaya, Moscow 117647, Russia Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1994) 22 (5): 455–458. https://doi.org/10.1130/0091-7613(1994)022<0455:MCESTC>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation M. D. Brasier, R. M. Corfield, L. A. Derry, A. Yu. Rozanov, A. Yu. Zhuravlev; Multiple δ13C excursions spanning the Cambrian explosion to the Botomian crisis in Siberia. Geology 1994;; 22 (5): 455–458. doi: https://doi.org/10.1130/0091-7613(1994)022<0455:MCESTC>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract New high-resolution δ13C data through the Lower Cambrian of Siberia reveal multiple, positive excursions coincident with phases in the "explosion" of invertebrate phyla (Nemakit-Daldynian to middle Botomian stages). Comparison of the δ18O and trace element (Mg, Fe, Mu, Sr) chemistry indicate that six new δ13C cycles are primary rather than diagenetic features, with potential for global correlation. Positive δ13C excursions up to +3‰ indicate that fractional organic carbon burial rates were high but variable through the Cambrian explosion. Values for δ13C dropped sharply from around +2.2‰ to -1.6‰ in Botomian time, coincident with mass extinction of the archaeocyathan reef biota. The rapid fluctuation of the δ13C signal and the temporal coincidence of the pronounced negative shift with the extinction event hint that the δ13C record may record productivity variations during the Early Cambrian radiation. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A total of 5754 ant inclusions from 13 European collections of Baltic, Bitterfeld, Rovno, and Scandinavian ambers are studied and identified as belonging to 147 species, 57 genera, and 9 subfamilies. The taxonomic composition and relative species abundances of species in representative collections are analyzed and considerable differences between the above four types of amber are shown. These differences appear to reflect differences in ecological conditions rather than in age. The Baltic and Bitterfeld ant assemblages are shown to be most similar, the Scandinavian assemblage turns out to be most dissimilar to these, and the Rovno assemblage is shown to be intermediate.

The term humic substances (HS) refers to a group of heterogeneous, dark-colored polydisperse substances found in soils, peats, natural waters, and sediments. It is hypothesized that HSs are formed as a result of degradation and transformation of biomolecules of organic residues and free radical condensation reactions (a process called humification). Humic substances are classified as a special category of natural compounds that are dissimilar to the biomolecules of plant and microbial tissues, and are resistant to biodegradation. On the basis of their solubility in alkalis, HSs are divided into humic acids (HAs, soluble, precipitated at pH < 2), fulvic acids (FAs, soluble at all pH values), and humin (insoluble residue). The review provides a critical analysis of the HS terminology and nomenclature, the method of extraction of HS from natural objects, and the hypotheses describing their formation. The ambiguity and duality of the concept of HSs (specific compounds and the sum of operational fractions) are demonstrated, as well as an arbitrary character of the division of organic matter (OM) into the dark-colored compounds of poorly defined structure (HSs) and the substances with a known structure (non-HSs). The interpretation of HSs as mass products of a secondary synthesis requires revision. The possibility of extracellular free radical reactions in soils leaves no doubt; however, a quantitative contribution of the corresponding products to the natural OM has not been established yet. The traditional alkaline extraction should be considered as a method for isolation of hydrophilic polar substances, while the precipitation with acid as their concentration for further analysis. The historical names of humic fractions (HAs, FAs, and humin) should be retained as well-established generic terms and names of the preparations obtained in a certain way without attaching unique features and specificity to all components of these fractions. The CHA/CFA (or CHA/Corg) ratios are simple and convenient indicators of the types of humus reflecting bioclimatic conditions of its formation.