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1.
Middle Devonian conodonts from the Si Phai section in NE Vietnam are described. The section ranges from the Middle Devonian ensensis to timorensis conodont zones to the Late Devonian rhomboidea conodont Zone. A rich overall assemblage is described, including 27 taxa of species or subspecies rank and 11 taxa described in an open nomenclature. Among the dominant Polygnathus forms, four new taxa are described: Polygnathus linguiformis saharicus subsp. nov., Polygnathus linguiformis vietnamicus subsp. nov., Polygnathus rhenanus siphai subsp. nov., and Polygnathus xylus bacbo subsp. nov. Conodont assemblages are attributed to polygnathid, polygnathid-klapperinid, and klapperinid conodont biofacies representing hemipelagic to pelagic environments. The klapperinid biofacies, unreported in the previous literature, are here attributed to offshore areas of the external shelf. The taxonomic compositions of the studied conodont assemblages, as well as their CAI characteristics (CAI 4–5), suggest a palaeogeographic affinity of the studied strata to the Chinese Devonian Guangxi Basin, and the South China Terrane in general. Furthermore, the conodont biofacies and the palaeogeographic distribution of the fauna are discussed.  相似文献   

2.
The Kellwasser Crisis represents one of the most severe extinction events in the Phanerozoic. The ?umbera section (Moravo-Silesian Basin, Moravian Karst) spans the Upper rhenana to Palmatolepis minuta minuta (or younger) conodont zones and corresponds to the upper part of a carbonate ramp with material derived from shallower areas. A rich association of calcareous algae, cyanobacteria, and microproblematica, comprising renalcids (Izhella), Girvanella, Rectangulina cf. tortuosa, Rothpletzella, “solenoporaceans”, “Keega”-like microfossils, udoteacean alga Paralitanaia, volvocean and radiospherid calcispheres, palaeoberesellids, Umbellina bella, and Wetheredella, is similar in diversity to associations known from China, Australia, Canada, and Belgium. The ?umbera section represents a unique locality where changes in shallow-water biota at the Frasnian-Famennian boundary are well calibrated by detailed conodont biostratigraphy. We track in detail the evolution of shallow-water biota and the features that are often discussed in the context of “anachronistic” facies, such as flourishing microbial structures, enhanced early marine cementation, and flat-pebble conglomerates. Some features which could be indicative of environmental stress such as flat-pebble conglomerates developed during the Frasnian part of the Kellwasser Crisis (Upper rhenana to linguiformis Zones), whereas a renalcid boom started at the Frasnian-Famennian boundary.  相似文献   

3.
A 50-m-thick section in the Po?áry quarry, Prague Syncline (Czech Republic) spanning the upper Silurian (uppermost Ludlow and P?ídolí) to the lowermost Devonian (Lochkovian) has been studied using sedimentological and physical stratigraphical (gamma-ray spectrometry) methods combined with conodont biostratigraphy. Conodont data demonstrate the presence of local conodont biozones: “Ozarkodina” crispa (uppermost Ludlow)—Zieglerodina zellmeri (base of P?ídolí)—Zieglerodina ivochlupaciDelotaxis detorta—“Ozarkodina” eosteinhornensis s.s.—Zieglerodina klonkensisIcriodus hesperius-optima (lowermost Lochkovian). The studied section represents a transgressive–regressive facies succession characterized by a transition from distal calciturbidites deposited in a distally steepened carbonate platform during transgression and sea-level highstand (crispa to lower ivochlupaci zones) to mixed calciturbidites/coarse-grained bioclastic limestones (falling-stage systems tract, upper ivochlupaci to lower klonkensis zones). The upper part of the succession consists of bioclastic limestones corresponding to a subtidal setting between storm-wave and fair-weather wave base (lowstand systems tract in upper klonkensis and hesperius-optima zones). This interpretation corresponds to the late Silurian global sea-level pattern as recorded in other regions. Thus the depositional system is interpreted as mostly driven by eustasy with short-lived periods of influence from local tectonics.  相似文献   

4.
Ammonoids from the basal beds of the Nerpalakh Formation (Lower Frasnian) of Belkovsky Island (New Siberian Archipelago) are systematically studied. Taxonomically, the assemblage studied (Manticoceras insulare sp. nov., Tornoceras typum (Sandberger, 1851), and T. contractum Glenister, 1958) is similar to the Early Frasnian ammonoid assemblage of South Timan, from which its is distinguished by the absence of the genera Timanites and Komioceras. The same beds contain conodonts of the Palmatolepis transitans Zone (= MN 4 Zone of the Montagne Noire standard succession), which allow the correlation of the beds studied with the Timanites keyserlingi and Komioceras stuckenbergi ammonoid zones of South Timan. The Early Frasnian ammonoids could supposedly have entered the region of the New Siberian Archipelago from the southwest at the time of a major transgression, which facilitated the distribution of the genera Manticoceras and Tornoceras. A new species of the genus Manticoceras is described.  相似文献   

5.
Supercalcified sponges, including sphinctozoans, inozoans, chaetetids, spongiomorphids, occurring in Upper Triassic (Norian-Rhaetian) shallow-marine limestones of Musandam Mountains in United Arab Emirates (UAE), are described. The following taxa were determined: sphinctozoans: Hajarispongia osmani Senowbari-Daryan and Yancey, Nevadathalamia arabica n. sp., Nevadathalamia conica n. sp., Fanthalamia milahaensis n. sp., Iranothalamia incrustans (Boiko), Cinnabaria regularis n. sp.; inozoans: Cavsonella triassica n. sp., Molengraaffia regularis Vinassa de Regny, Peronidella? sp., Circopora cf. caucasica Moiseev, Circopora? sp.; spongiomorphids: Spongiomorpha sp.; chaetetids: Lovcenipora chaetetiformis Vinassa de Regny, Lovcenipora musandamensis n. sp., Lovcenipora sp., chaetetid sponge gen. et sp. indet. The most abundant sponge in the studied material is Nevadathalamia arabica n. sp. The described sponge association of the Arabian shelf (Musandam Mountains) shows close affinity to the sponge association known from age-equivalent terranes in the Panthalassa Ocean (Sonora Mountains in Mexico; Pilot Mountains in Nevada, USA), but is remarkably different from sponge associations in carbonates bordering the Tethys. This difference goes along with the biogeography of wallowaconchid bivalves and is most likely attributed to climatic, palaeogeographic or oceanographic factors.  相似文献   

6.
Melanosclerites, a little-known group of organic microfossils, are recorded for the first time from the Lower Silurian Wilhelmi Formation, Illinois, USA. The taxa described herein include Melanorhachis regularis Eisenack, 1942, Melanoarbustum balticum Górka 1971, Melanocyathus dentatus Eisenack, 1942, Eichbaumia incus? Schallreuter, 1981, Menola os Schallreuter, 1981 and Melanoporella clava Schallreuter, 1981.  相似文献   

7.
Phylogeographic patterns of Ammopiptanthus in northwestern China were examined with internal transcribed spacer (ITS) and three chloroplast intergenic spacers (trnH–psbA, trnL–trnF, and trnS–trnG). Two ITS genotypes (a–b) and 8 chloroplast haplotypes (A–H) were detected. Both ITS genotypes and chloroplast lineages were split in two geographic regions: western Xinjiang and the Alxa Desert. This lineage split was also supported by AMOVA analysis and the Mantel test. AMOVA showed that 89.81 % of variance in Ammopiptanthus occurred between the two geographic regions, and correlation between genetic distances and geographical distances was significant (r = 0.757, p < 0.0001). All populations in western Xinjiang shared haplotype A with high frequency, and range expansion was strongly supported by negative Fu’s FS value, and mismatch distribution analysis, whereas populations in the Alxa Desert had higher genetic diversity and structure. We speculate that the cold and dry climate during the early Quaternary fragmented habitats of the species, limiting gene flow between regions, and interglacial periods most likely led to the range expansion in western Xinjiang. The low genetic diversity of Ammopiptanthus indicate a significant extinction risk, and protective measures should be taken immediately.  相似文献   

8.
Efforts to mitigate amphibian declines are hindered by a lack of information about basic aspects of their biology and demography. The effective to census population size ratio (N e /N c ) is one of the most important parameters for the management of wildlife populations because it combines information on population abundance and genetic diversity and helps predict population viability in the long term. Few studies have calculated this ratio in amphibians, which sometimes show low ratios, associated with a higher extinction risk. Here we integrate field-based (capture-mark-recapture studies, egg string counts) and molecular approaches (estimation of the effective number of breeders (N b ) and the effective population size (N e ) based on genotypes from larval cohorts and candidate parents) to produce the first estimates of the N e /N c and N b /N c ratios in two amphibians, the Iberian ribbed newt Pleurodeles waltl and the western spadefoot Pelobates cultripes. Additionally, we investigate sex-biased dispersal in both species based on direct (field observations) and indirect (genetic) evidence. Both species showed similar ratios, slightly lower in Pleurodeles (0.21–0.24) than in Pelobates (0.25–0.30). Observed displacement rates were low in both species (P. waltl?=?0.51%; P. cultripes?=?1.23%). We found no evidence for sex-biased dispersal in P. cultripes, but both direct and indirect evidences suggest a tendency for female-biased dispersal in P. waltl. We discuss differences in the genetic estimates of N e and N b provided by three inference methods and the implications of our findings for the management of these species, characteristic of Mediterranean wetlands in the Iberian Peninsula and listed as Near Threatened.  相似文献   

9.
The recent recognition of the earliest Andean Tithonian ammonite fauna (Picunleufuense Zone) has allowed a balanced classification of the ataxioceratid ammonites, reflecting their phylogenetic relationships. The Picunleufuense Zone fauna, first recognized in the Neuquén Basin at the base of the Vaca Muerta Formation, is represented by numerous records of sparse ammonite faunas from Antarctica, the Austral Basin and the Tarapacá Basin (N. Chile and S. Peru). These Southeastern Pacific faunas include the Tithonian genera Indansites, Choicensisphinctes, Zapalia, Krantziceras (Tithonian–lower Berriasian) and Platydiscus. These five genera are grouped in a new subfamily established in this paper: Zapaliinae subfam. nov. (type genus: Zapalia). The origin of Indansites and Choicensisphinctes (possibly via Indanistes) from Lithacoceras is discussed. Zapalia must have been originated from Indanistes in the upper Proximus Zone. Platydiscus could have been originated from Krantziceras. The Tithonian Southeastern Pacific ataxioceratids (Zapaliinae subfam. nov.) form a group well separated from the Tithonian Indo-Madagascan Virgatosphinctinae.  相似文献   

10.
The faunas living in the vast deep sea regions around the Antarctic are very poorly known. This is especially true for the biodiversity of polychaetes inhabiting these remote areas. Therefore, we report new morphological data of Glyceriformia from the ANDEEP cruises to the South Atlantic Ocean and the Southern Ocean. Based on benthos samples from three expeditions aboard R/V POLARSTERN, two species of Glyceridae (Glycera capitata, G. diva) and four species of Goniadidae (Bathyglycinde sibogana, B. stepaniantsae, Goniada maculata, Progoniada regularis) were studied. Furthermore, new morphological details (especially for the previously unknown tail) for the rarely found taxon B. stepaniantsae are given. The distribution patterns of the different taxa demonstrated that some species have a high dispersal capability and show an extended level of eurybathy, whereas other species are restricted to the deep sea.  相似文献   

11.
In this study we are concerned with the general problem of choosing from a set of endangered species T a subset S of k species to protect as a priority. Here, the interest to protect the species of S is assessed by the resulting expected phylogenetic diversity (ePD) of the set T, a widely used criterion for measuring the expected amount of evolutionary history associated with T. We consider that the survival of the protected species is assured and, on the contrary, that there is a risk of extinction for the unprotected species. The problem is easy to solve by a greedy type method if the extinction probabilities of the unprotected species are known but these probabilities are generally not easy to quantify. We show in this note that the choice of the precise values attributed to the extinction probabilities—provided it respects the rank of imperilment of each species—is not as decisive as might be feared for the considered problem. The values of these probabilities have a clear impact on the selection of the species to be protected but a little impact on the resulting ePD. More precisely, if T 1 and T 2 are the two optimal subsets of species corresponding to two scenarios (two different sets of probabilities) the ePDs of T 1 and T 2, calculated with the probabilities of the first scenario—or with the probabilities of the second scenario—are not very different.  相似文献   

12.
Borehole Nizhny Imbak 219 is situated in the northwestern Siberian Platform. Paleontological material comes from the clayey–limestone series at a depth of 2333.3–2314.3 m referred to the Ovatoryctocara and Kounamkites zones of the Middle Cambrian Amgan Stage and from the overlying limestone series at a depth of 2264.1–2244.0 m referred to the upper part of the Kounamkites Zone and an unnamed zone of the Amgan Stage and also to the Solenopleura patula and Dorypyge olenekensis–Corynexochus perforatus zones of the Middle Cambrian Mayan Stage. The questions of the traditional Lower–Middle Cambrian boundary and the role of Siberian sections in the construction of the International Chronostratigraphic Chart are considered. The trilobites collected are described.  相似文献   

13.
An investigation of the wavelength dependent extinction spectra of coated sphere with different core@shell compositions based on discrete dipole approximation technique has been presented in this paper. We have used combinations of A g, A u, and S i O 2 for this analysis. Specifically, we study the impact of spherical core-shell thickness on its surface plasmon resonance (SPR) peak positions and corresponding spectral widening in distinct regimes of the spectrum. We observe that SPR peak of core-shell nanoparticle(CSNP) can be tuned over the visible to near-infrared spectrum region by manipulating the core/shell ratio and composition of core and shell. Specifically, for dielectric@metal (core@shell) nanoparticle, SPR peak position shifted towards lower wavelength as we increase the shell thickness, which is opposite to the SPR behavior of metal@dielectric. The extinction spectrum shows linear relation between SPR position and thickness of the shell. Further, we observed two resonant peaks for the case of metal@metal CSNP. The SPR peak of Au@Ag (a eff 100 nm with shell thickness 8 nm) reveals two resonant peak corresponding to Au (594 nm) in red domain, while the peak in blue domain corresponds to Ag (402 nm). We also observe that optical resonance of CSNP can be tuned across the near-infrared region by changing the surrounding medium of higher refractive index. Further, near field pattern of core@shell geometry at resonance wavelength is also shown in the present study. We have also compared the numerical and analyticalmethod for smaller size CSNP with varying thickness and the results show good agreement.  相似文献   

14.
Saussurea involucrata (Asteraceae) is a medicinal and second-degree national priority endangered plant that is mainly distributed in the high latitude region of the western Tianshan Mountains. The population is fragmented and isolated, and extensive human impact merits a suitable and specific conservation strategy, which can be compiled based on the genetic diversity, population structure, and demographic history. Phylogeographic studies were conducted on a total of five natural populations and 150 individuals were sampled. Data from three cpDNA intergenic spacer regions (trnL-F, matK, and ndhF-rpl32) and nrDNA ITS sequences showed that twelve haplotypes in cpDNA and five haplotypes in nrDNA indicated high genetic diversity among populations sampled (H T?=?0.820 and 0.756) and within populations sampled (H S?=?0.792 and 0.721). Additionally, the high genetic diversity did not mirror genetic structure in either cpDNA (F ST?=?0.03153, G ST?>?N ST, p?<?0.05) or nrDNA (F ST?=?0.03666, meaningless G ST and N ST). Two groups (north and south) were determined for a SAMOVA analysis. Based on this analysis, the demographic history was conducted with a Bayesian Skyline Plot and Isolation with Migration analysis, which showed sustainable and stable extension without a marked bottleneck. Divergence time was indicated at c. 6.25 Mya (90%HPD: 15.30–0.22 Mya) in the Miocene, which is consistent with the formation of the Kelasu section of Tianshan. The southern populations in the Bayanbulak and Gonglu regions require additional attention and transplanting would be an effective way to restore rare cpDNA haplotypes, increase effective population size, and migration rate. Our results suggested that in situ conservation of S. involucrata in western Tianshan should be the main strategy for protection and recovery of the species.  相似文献   

15.
The maximum exergy dissipation theory provides a theoretical basis for using surface temperature to measure the status and development of ecosystems, which could provide an early warning of rapid evaluation of ecosystem degradation. In the present study, we used the radiation balance of ecosystems to demonstrate this hypothesis theoretically. Further, we used empirical data to verify whether ecosystems gain more radiation, while lowering their surface temperatures, as they develop naturally. We analyzed 12 chronosequences from the FLUXNET database using meteorological data and heat fluxes. We included age, disturbance, and successional chronosequences across six climate zones. Net radiation (R n) and the ratio of net radiation to global radiation (R n/R g) were used to measure the energy gain of the ecosystems. The maximum daily air temperature above the canopy (T max) and thermal response number (TRN) were used to analyze the surface temperature trends with ecosystem natural development. The general trends of T max, TRN, R n, and R n /R g demonstrated that ecosystems become cooler and more stable, yet gain more energy, throughout their natural development. Among the four indicators, TRN showed the most consistent trends and highest sensitivity to ecosystem growth, succession, and recovery. Moreover, TRN was not significantly influenced by precipitation or wind. We propose that TRN can be used to rapidly evaluate or warn of ecosystem disturbance, senescence, and degradation without prior knowledge of species composition, nutrient status, and complex ecosystem processes.  相似文献   

16.
《Palaeoworld》2022,31(3):428-442
The Himalaya Terrane of southern Tibet exposes successive shallow-marine carbonate deposits from the Lower to Upper Triassic, and is a key region for studying the Triassic conodont biostratigraphy at the northern margin of the Indian Plate. On the basis of newly collected samples from the Kangshare and Laibuxi formations at the Tulong section, 11 conodont species of 7 genera were identified, and four conodont zones were established, namely, the Novispathodus abruptus Zone (lower Spathian, first reported in Tibet), the Columbitella jubata Zone (middle Spathian), the Triassospathodus symmetricus Zone (upper Spathian), and the Chiosella timorensis Zone (lowermost Anisian) in ascending order. The first occurrence (FO) of Chiosella timorensis indicates the Olenekian–Anisian boundary (OAB) at Bed 25, upper part of the Kangshare Formation. The regional and global correlation of these conodont zones is synthesized.  相似文献   

17.
The brachiopods (e.g., Heterelasma sp. nov., Uniplicatorhynchia sp. nov., Quadratirhynchia sp., and Sphriganaria sp.) discovered from the Olenekian deposits of the Kamenushka River basin and Russky Island, South Primorye, allow refining the information on the stratigraphic range of the relevant families and recovery of the biota after the Late Permian mass extinction. A new terebratulid genus, Bittnerithyris gen. nov., and a new rhynchonellid species, Piarorhynchella tazawai sp. nov., are established.  相似文献   

18.
Seasonal changes in the characteristics of chlorophyll fluorescence were studied in the bark of several species of trees originating in various climatic zones: Siberian cedar (Pinus sibirica), larch (Larix sibirica), eastern arborvitae (Thuja occidentalis), pendent white birch (Betula pendula), wild black cherry (Padus virginiana), horse chestnut (Aesculus hippocastanum), red oak (Quercus rubra), Manchurian catalpa (Catalpa bungei), linden (Tilia cordata), goat willow (Salix caprea), Amur cherry (Padus maackii), and apple Korichnaya (Malus domestrica B.). Tree bark has a sufficient amount of chlorophyll for measuring the parameters of chlorophyll fluorescence throughout the year. The relative yield of the variable fluorescence of chlorophyll (F v/F m) can be used to assess seasonal changes in the physiological state of various trees.  相似文献   

19.
Eight bryozoan species of the order Cystoporida are described from the Emsian Stage of the Lower Devonian in the western Altai-Sayan Folded Area. Five of them are new species: Fistulipora salairiensis sp. nov., Fistuliramus fasciculus sp. nov., Fistuliphragma sibirica sp. nov., F. moniliformis sp. nov., and Fistulocladia cincinnata sp. nov. The others belong to the genera Ganiella, Physallidopora, and Fistuliporidra. Most of the cystoporid species studied from the Emsian Stage in the Altai-Sayan Folded Area are widespread laterally. Six cystoporid species have a narrow stratigraphic range and are, therefore, characteristic species of the bryozoan biostratigraphic zones of this region. The species of Physallidopora cantabrica Ernst et Buttler and Fistuliporidra hibera Ernst et Buttler, for the first time encountered in the Emsian of Gorny and Rudny Altai, were previously described from coeval deposits in northwestern Spain.  相似文献   

20.
A new conodont species, Polygnathus postvogesi sp. nov., from the Tournaisian deepwater deposits of the northern Urals, southeastern part of the Chernyshev Ridge, and central Pai-Khoi is described. The new species continue the phylogenetic lineage of the Late Devonian polygnathid P. marginvolutus Gedik, P. vogesi Ziegler.  相似文献   

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