The first record of Cambrian conodonts from the Huqf-Haushi outcrops, Oman, Arabian Peninsula.

Outcrops of Cambrian sediments of the uppermost Miqrat Formation, the Al Bashair Formation and the basal Barik Formation were sampled for conodont and palynomorph studies. The units are part of the Palaeozoic Haima Supergroup, exposed in the Huqf-Haushi area in central eastern Oman, Arabian Peninsula. Palynomorphs were absent but conodont samples yielded a small conodont fauna. The presence of Muellerodus? erectus allows the recognition of the Muellerodus? erectus Zone established for North China (late Paibian – early Jiangshanian), in accordance with previous reports on the trilobite fauna from the same interval

THE FIRST RECORD OF CAMBRIAN CONODONTS FROM THE HUQF-HAUSHI OUTCROPS, OMAN, ARABIAN PENINSULA

Outcrops of Cambrian sediments of the uppermost Miqrat Formation, the Al Bashair Formation and the basal Barik Formation were sampled for conodont and palynomorph studies. The units are part of the Palaeozoic Haima Supergroup, exposed in the Huqf-Haushi area in central eastern Oman, Arabian Peninsula. Palynomorphs were absent but conodont samples yielded a small conodont fauna. The presence of Muellerodus? erectus allows the recognition of the Muellerodus? erectus Zone established for North China (late Paibian – early Jiangshanian), in accordance with previous reports on the trilobite fauna from the same interval

CONODONTS FROM THE WA’ERGANG SECTION, CHINA, A POTENTIAL GSSP FOR THE UPPERMOST STAGE OF THE CAMBRIAN

Furongian (upper Cambrian) conodonts from the Shenjiawan Formation, Wa’ergang section, Taoyuan County, Hunan Province, South China are described. The Wa’ergang section has been proposed as a potential GSSP for the base of the uppermost stage of the Cambrian System, at the first appearance of the agnostoid trilobite Lotagnostus americanus. The Shenjiawan Formation consists of limestone with intercalations of marlstone and shale. The conodont yielding is low and the preservation is moderate. The conodont fauna includes proto-, para- and euconodonts. Conodont taxa characteristic of North China, South China and Korea occur together with cosmopolitan taxa. The biostratigraphic distribution of conodonts is directly correlated with the agnostoid trilobite biozones, with the base of the Proconodontus posterocostatus Zone very close to the base of the Lotagnostus americanus trilobite Zone

The secondary metabolite euplotin c induces apoptosis-like death in the marine ciliated protist euplotes vannus

The sesquiterpenoid euplotin C is a secondary metabolite produced by the ciliated protist Euplotes crassus and provides a mechanism for damping populations of potential competitors. Indeed, E. crassus is virtually resistant to its own product while different non-producer species representing an unbiased sample of the marine, interstitial, ciliate diversity are sensitive. For instance, euplotin C exerts a marked disruption of different homeostatic mechanisms in Euplotes vannus. We demonstrate by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay that euplotin C quickly decreases viability and mitochondrial function of E. vannus with a very high efficacy and at micromolar potency. In addition, euplotin C induces apoptosis in E. vannus as 4,6-diamino-2-phenylindole and Terminal Transferase dUTP Nick End Labeling staining show the rapid condensation and fragmentation of nuclear material in cells treated with euplotin C. These effects occur without detectable permeabilisation or rupture of cell membranes and with no major changes in the overall morphology, although some traits, such as vacuolisation and disorganised microtubules, can be observed by transmission electron microscopy. In particular, E. vannus show profound changes of the mitochondrial ultrastructure. Finally, we also show that caspase activity in E. vannus is increased by euplotin C. These data elucidate the pro-apoptotic role of euplotin C and suggest a mechanism for its impact on natural selection.L'articolo è disponibile sul sito dell'editore http://onlinelibrary.wiley.com

Preuves paléontologiques d'un âge Cambrien supérieur dans la région d'Arburese, SW de la Sardaigne

New palynological investigations allowed a better definition of the age of terrigenous deposits of the Monte Fonnesu tectonic Unit, exposed in the Arburese area (SW Sardinia). The section investigated consists of a coarsening upwards positive sequence, up to 10 m thick, that is made up of quartz-arenitic sandstones and light gray quartzite beds (0.5 m thick), interbedded with thin beds of black shale. In the lower part of the section, two quartzitic levels are rich in lingulid (brachiopods) shell fragments. This is the first report of macrofossils from the Monte Fonnesu Unit. Samples collected for palynological analyses in the black shale at the base and at the top of the lowest quartzitic level yielded a Late Cambrian acritarch microflora that can be correlated with the Peltura trilobite Superzone. The Late Cambrian age assigned to the lower part of the sequence allows us to define more precisely the age of Mt. Fonnesu sandstone, which in consequence is bracketed between the Late Camb..

The Xiaoyangqiao section, Dayangcha, North China: the new global Auxiliary Boundary Stratotype Section and Point (ASSP) for the base of the Ordovician System

In 2019 the Sub-Commission on the Ordovician System approved the Xiaoyangqiao section, North China as a new ASSP section for the base of the Ordovician System. The sedimentary succession of the section is exposed in a natural outcrop near the Dayangcha Village at a position of 42°3'24''N, 126°42'21''E. It has a well-preserved, abundant and diverse fossil record across the boundary with key markers (conodonts and graptolites), which provide improved intercontinental correlation of the Cambrian– Ordovician boundary. The appearance of the first planktonic graptolites is immediately below the base of the Cordylodus lindstromi Conodont Zone. Other fossils, including acritarchs, brachiopods and trilobites are also present in the Xiaoyangqiao ASSP section. Non-biotic secondary global markers near the base of the Ordovician System include a positive carbon isotopic excursion with the maximum peak (named HSS) below the boundary, a prominent unnamed negative peak immediately below the boundary and a prominent carbon isotope excursion with positive peaks above the boundary. The latter excursion is associated with the appearance of the planktonic graptolites in the Ordovician. The strength of the Xiaoyangqiao ASSP section is the correlation between the conodonts and graptolites, correspondence of sea-level lowstands, and the matches of geochemical parameters

The detailed Middle to early Late Ordovician faunal succession and δ13Ccarbon chemistry of the Kårehamn drill core, offshore eastern Öland, Sweden: implications for stratigraphy and correlation

The Middle to lower Upper Ordovician stratigraphy of the KÃ¥rehamn core, drilled ca 7 km offshore to the east of the KÃ¥rehamn village, northeastern Ãland, is presented. The investigated core is one of four drill cores obtained during the preparation of the KÃ¥rehamn offshore wind farm. It is ca 41 m long and has a diameter of 10 cm. The lithostratigraphy, faunal (conodonts and chitinozoans) succession and δ13Ccarbon isotope chemistry pattern are built upon this complete core. The drilling stopped at 64.5 m b.s.l. in the Swedish Orthoceratite limestone, within the upper Lenodus variabilis Conodont Zone. The horizon is largely equivalent to the strata that in Sweden were previously named âlimestone with Asaphus âranicepsââ, which is within the Orthoceratite limestone. It is characterized by and composed of mainly light-grey, highly fossiliferous and stylolitic limestone with little clay material. The next unit includes the Yangtzeplacognathus crassus and lower Lenodus pseudoplanus conodont zones. The upper Lenodus pseudoplanus (with Microzarkodina ozarkodella late form sensu Lindström), Eoplacognathus suecicus and E. foliaceus conodont zones are recorded from the overlying succession of the upper Orthoceratite limestone. This interval corresponds to the Segerstad, Skärlöv and Seby topoformations of Jaanusson, all of which are included in the upper part of the Swedish Orthoceratite limestone. The prominent δ13Ccarbon isotope MDICE peak recorded from the KÃ¥rehamn drill core is biostratigraphically precisely assigned to the upper part of the newly redefined Eoplacognathus suecicus Conodont Zone. The conformably overlying Folkeslunda Limestone is the top unit of the Orthoceratite limestone; it is composed of lime mudstone and grey bedded wackestone. Biostratigraphically, it is referred to the Eoplacognathus reclinatus Subzone of the Pygodus serra Conodont Zone corresponding to the lower part of the Laufeldochitina striata Chitinozoan Zone. The Furudal Limestone â on Ãland known as the Källa Limestone and Persnäs Limestone â overlies the Orthoceratite limestone and represents an important change of the depositional environment in the Baltic Basin. The Källa Limestone contains the Eoplacognathus robustus Conodont Subzone of the Pygodus serra Conodont Zone and the Laufeldochitina striata Chitinozoan Zone. Pygodus protoanserinus Zhang is the transitional taxon from P. serra to P. anserinus and is securely and precisely recorded for the first time in the region. The important conodont species Pygodus anserinus Lamont and Lindström is recorded from the Persnäs Limestone (= upper Furudal Formation) from which also theLaufeldochitina striata Chitinozoan Zone is documented. Pygodus anserinus extends into the overlying Dalby Formation, in which it is succeeded by the lower Amorphognathus tvaerensis Conodont Zone. The diagnostic chitinozoans Eisenackitina rhenana, Laufeldochitina stentor, Conochitina savalaensis, Belonechitina intonsa and Conochitina viruana are well documented from the same formation. The top of the core is within the Baltoniodus variabilis Conodont Subzone of theAmorphognathus tvaerensis Conodont Zone of the Bergström conodont zonation. The precise integrated biostratigraphy of the conodonts and chitinozoans along with the carbon isotope curve are results of this study, which largely agree with those of previous research of the Baltic Basin and thus provide data for precise correlation across the Baltic Basin. The fossil assemblages are clearly related to the east Baltic chronostratigraphic scheme and to the new chronostratigraphic scheme of Scandinavia, and the succession is referred to the established stages of the two systems

A global view on the Ordovician stratigraphy of south-eastern Europe

The Ordovician documented in south-eastern Europe reflects different sedimentary environments, from shallow water to basin, belonging to diverse palaeogeographical domains. Some of these geological sectors and their palaeontological content have been well described for a long time, like the Carnic Alps, that represent one of the most continuous Palaeozoic sequence in the world. For some other areas, the quality of the data is variable and the knowledge is less detailed, sometimes with lithostratigraphic units still to be formalized, also reflecting the fragmentary nature of the outcrops. The Ordovician stratigraphy of diverse successions of south-eastern Europe has been herein revised and integrated with new data in the attempt of detecting a global scenario for this critical time interval in the evolution of life.This research was undertaken within the framework and with the financial support of the Spanish Ministry of Science and Innovation, project PID2021-125585NB-100 (to JCG-M and JC).Peer reviewe