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Sedimentary ancient DNA shows terrestrial plant richness continuously increased over the Holocene in northern Fennoscandia
No full textThe effects of climate change on species richness are debated but can be informed by the past. Here, we generated a sedimentary ancient DNA dataset covering 10 lakes and applied novel methods for data harmonization. We assessed the impact of Holocene climate changes and nutrients on terrestrial plant richness in northern Fennoscandia. We find that richness increased steeply during the rapidly warming Early Holocene. In contrast to findings from most pollen studies, we show that richness continued to increase thereafter, although the climate was stable, with richness and the regional species pool only stabilizing during the past three millennia. Furthermore, overall increases in richness were greater in catchments with higher soil nutrient availability. We suggest that richness will increase with ongoing warming, especially at localities with high nutrient availability and assuming that human activity remains low in the region, although lags of millennia may be expected.The study is part of the ECOGEN project “Ecosystem change and species persistenceover time: A genome-based approach,” financed by Research Council of Norway grant 250963/F20. The publication charges for this article have been partially funded by a grant from the publication fund of UiT The Arctic University of Norway</p
Pyritized preservation of chancelloriids from the Cambrian Stage 3 ofSouth China and implications for biomineralization
No full textThe enigmatic Cambrian animal chancelloriids were discovered in a wide range of taphonomic settings; however, preservation of biomineralized sclerite microstructure was solely known from secondarily phosphatized skeletal remains. Here, we investigate a uniquely pyritized chancelloriid from the lowerCambrian Guojiaba Formation in southern Shaanxi Province, China, using a combination of advanced analytic techniques. Results of the energy dispersive spectroscopy (EDS), X-Ray Fluorescence (XRF), and Raman spectrum show that the sclerites and scleritomes are preserved as pyritized internal moulds witha calcitic outer layer. The outer layer enveloping the internal moulds likely represents the recrystallized counterpart of the original biomineralized sclerite wall. Distinctive fibrous microstructures are discovered in the sclerites, which echo the features seen in the phosphatized fossils of chancelloriids. The typical microstructure, along with the recrystallized calcite, corroborate the interpretation that chancelloriid sclerites were originally constructed by fibrous aragonite. The stability of the microstructure and mineral composition in both carbonate and siliciclastic backgrounds indicate that chancelloriids were adapted to exploit aragonitic fibres to build their skeletons regardless of the change of their living environments.This study was supported by National Key Research and Development Program (grant number 2017YFC0603101), National Natural Science Foundation of China (grant numbers 41621003, 41890840, 41930319, and 42002011), the Strategic Priority Research Program of Chinese Academy of Sciences (grant number XDB26000000), the 111 Project (grant number D17013), and China Postdoctoral Science Foundation (grant number 2019M663793).</p
Crittendenia gen. nov., a new lichenicolous lineage in the Agaricostilbomycetes (Pucciniomycotina), and a review of the biology, phylogeny and classification of lichenicolous heterobasidiomycetes.
No full textThe neurocranium of Ekweeconfractus amorui gen. et sp. nov. (Hyaenodonta, Mammalia) and the evolution of the brain in some hyaenodontan carnivores
No full textThis project forms part of the NSF-funded Research on East African Catarrhine and Hominoid Evolution (REACHE) Project and is REACHE Paper #16. Fieldwork by The West Turkana Miocene Project was funded by NSF award BCS 1241817 to JBR, the Natural Sciences and Engineering Research Council of Canada, and the University of Calgary.</p
Perfluoroalkyl substances in circum-ArcticRangifer: caribou and reindeer
No full textLivers of caribou and reindeer (Rangifer tarandus) from Canada (n = 146), Greenland (n = 30), Svalbard (n = 7), and Sweden(n = 60) were analyzed for concentrations of eight perfluoroalkyl carboxylic acids and four perfluoroalkane sulfonic acids. InCanadian caribou, PFNA (range < 0.01–7.4 ng/g wet weight, ww) and PFUnDA (<0.01–5.6 ng/g ww) dominated, whereasPFOS predominated in samples from South Greenland, Svalbard, and Sweden, although the highest concentrations were found incaribou from Southwest Greenland (up to 28 ng/g ww). We found the highest median concentrations of all PFAS except PFHxSin Akia-Maniitsoq caribou (Southwest Greenland, PFOS 7.2–19 ng/g ww, median 15 ng/g ww). The highest concentrations ofΣPFAS were also found in Akia-Maniitoq caribou (101 ng/g ww) followed by the nearby Kangerlussuaq caribou (45 ng/g ww),where the largest airport in Greenland is situated, along with a former military base. Decreasing trends in concentrations wereseen for PFOS in the one Canadian and three Swedish populations. Furthermore, PFNA, PFDA, PFUnDA, PFDoDA, andPFTrDA showed decreasing trends in Canada’s Porcupine caribou between 2005 and 2016. In Sweden, PFHxS increased inthe reindeer from Norrbotten between 2003 and 2011. The reindeer from Västerbotten had higher concentrations of PFNA andlower concentrations of PFHxS in 2010 compared to 2002. Finally, we observed higher concentrations in 2010 compared to 2002(albeit statistically insignificant) for PFHxS in Jämtland, while PFNA, PFDA, PFUnDA, PFDoDA, and PFTrDA showed nodifference at all
Fossil seed fern Lepidopteris ottonis from Sweden records increasing CO2 concentration during the end-Triassic extinction event
No full textThe end-Triassic event (ETE), a short global interval occurring at the end of the Triassic Period (~201.5 Ma), was characterized by climate change, environmental upheaval, as well as widespread extinctions in both the marine and terrestrial realms. It was associated with extensive perturbations of the carbon cycle, principally caused by the volcanic emplacement of the Central Atlantic Magmatic Province in relation to the break-up of Pangea. The correlated change in atmospheric CO2 concentrations (pCO2) can be reconstructed with the stomatal proxy, which utilizes the inverse relationship between stomatal densities of plant leaves (here stomatal index (SI), which is the percentage of stomata relative to epidermal cells) and pCO2. Fossilized Lepidopteris leaves are common and widespread in Triassic strata, thus offering great potential for high-resolution pCO2 reconstructions. A dataset of leaf cuticle specimens belonging to the seed fern species Lepidopteris ottonis from sedimentary successions in Skåne (Scania), southern Sweden, provided the possibility of pCO2 reconstruction at the onset of the ETE. Here, we tested the intra- and interleaf variability of L. ottonis SI, and estimated the pCO2 during the onset of the ETE. Our findings confirm L. ottonis as a valid proxy for palaeo-pCO2, also when using smaller leaf fragments. Importantly, the statistical analyses showed that the SI values of abaxial and adaxial cuticles are significantly different, providing a tool to distinguish between the two sides and select cuticles for analysis. Reconstructed pCO2 increased from ~1000 pre ETE to ~1300 ppm at the onset of the event, a significant increase of ~30% over a relatively short time period. The pCO2 recorded here is similar to previously published estimates, and strongly supports the observed pattern of elevated pCO2 at the onset of the ETE.Also funded by the Bolin Centre for Climate Research and an ERASMUS+ (EuRopean Community Action Scheme for the Mobility of University Students) for financial support for M.Sl.</p
Timescales of impact melt sheet crystallization and the precise age of the Morokweng impact structure, South Africa
No full textImpact cratering was a fundamental geological process in the early Solar System and, thus, constraining the timescales over which large impact structures cool is critical to understanding the thermal evolution and habitability of early planetary crusts. Additionally, impacts can induce mass extinctions and establishing the precise timing of the largest impacts on Earth can shed light on their role in such events. Here we report a high-precision zircon U–Pb geochronology study of the Morokweng impact structure, South Africa, which appears to have a maximum present-day diameter of ∼80 km. Our work provides (i) constraints on the cooling of large impact melt sheets, and (ii) a high-precision age for one of Earth's largest impact events, previously proposed to have overlapped the ca. 145 Ma Jurassic–Cretaceous (J–K) boundary. High-precision U–Pb geochronology was performed on unshocked, melt-grown zircon from five samples from a borehole through approximately 800 m of preserved impact melt rock. Weighted mean 206Pb/238U dates for the upper four samples are indistinguishable, with relative uncertainties (internal errors) of better than 20 ka, whereas the lowermost sample is distinguishably younger than the others. Thermal modeling suggests that the four indistinguishable dates are consistent with in situ conductive cooling of melt at this location within 30 kyr of the impact. The younger date from the lowest sample cannot be explained by in situ conductive cooling in line with the overlying samples, but the date is within the ∼65 kyr timeframe for melt-present conditions in footwall rocks below the impact melt sheet that is indicated by our thermal model. The Morokweng impact event is here constrained to 146.06 ± 0.16 Ma (2σ; full external uncertainty), which precedes current estimates of the age of the J–K boundary by several million years
The youngest known tommotiid: Lapworthella bornholmiensis (Poulsen, 1942) from Cambrian Stage 4 to Guzhangian (Miaolingian) strata of Bornholm and southern Sweden
No full textThe Camenellan tommotiid Lapworthella bornholmiensis is systematically revised based on the original type material and collections of Small Shelly Fossils at the Swedish Museum of Natural History. The species is clearly differentiated from all other species of Lapworthella by its unique surface ornamentation. Variability in sclerite shape is analyzed among the 39 specimens and four sclerite morphotypes are recognized: bilaterally subsymmetrical A sclerites with straight apertural margin and subrectangular to subelliptical cross-section; asymmetrical B sclerites with oblique to curved apertural margin and subrectangular to subelliptical cross-section; asymmetrical C sclerites with one concave surface resulting in elliptical to sub-triangular cross section; elongated asymmetrical D sclerites with subcircular cross section. The C sclerites are further divided into two sub-types. The sclerite morphotypes of Lapworthella bornholmiensis allow a detailed comparison with other lapworthellid taxa and we identify a pattern of recurring sclerite morphotypes across a range of species, allowing a new understanding of the lapworthellid scleritome structure. The stratigraphic range of Lapworthella bornholmiensis includes the Cambrian Stage 4 Gislöv Formation, the Wuliuan-Drumian Forsemölla and Exsulans Limestones in the Alum Shale Formation and Guzhangian limestone fill in Proterozoic basement fissures in Bohuslän, making this long ranging species the youngest known tommotiid in the fossil record
On the discovery of ferromanganese nodules in the world ocean
No full textFor a century, the discovery of ferromanganese (Fe–Mn) nodules in the World Ocean was universally and indisputably credited to the Challenger circum-global oceanographic expedition of 1872–1876, during which the first manganese nodules and crusts were dredged up from the sea floor in February–March 1873. A century later, a counterclaim appeared in the literature, crediting Nordenskiöld’s expedition on Sofia in 1868, five years before the Challenger findings, for the discovery of Fe–Mn nodules in the ocean. This counterclaim, widely accepted without scrutiny, was based on the Gustaf Lindström (1884) chemical analysis of a single bottom sediment sample among 14 samples from two Arctic expeditions led by Nordenskiöld:Sofia 1868 and Vega 1878–1880. The Lindström (1884) report published as an eight-page brochure in Swedish remained almost unknown to the research community until now. A close examination of this report and other historical evidence revealed that the counterclaim of discovery by the Sofia 1868 expedition to the Kara Sea is invalid based on three notable facts: (1) Sofia never sailed in the Kara Sea; (2) the single bottom sediment sample with an extremely high content of Mn (24%), was collected in the Kara Sea during the Vega Expedition across the Northeast Passage; (3) the Vega sampling was in 1878, not in 1868. Meanwhile, five and a half years prior to the Vega sampling, the first Fe–Mn nodules and crusts were dredged up from the sea floor on 18 February and March 7, 1873 during the Challenger expedition. These findings have been promptly reported and published in May 1873. Thus, the credit for the discovery of ferromanganese nodules in the World Ocean firmly belongs to the Challenger expedition
Soft part preservation in hyolithids from the lower Cambrian (Stage 4) Guanshan Biota of South China and its implications
No full textHyoliths, known globally from the Cambrian to the Permian are generally recognized as early lophotrochozoan animals of uncertain phylogenetic position. The calcareous exoskeleton of hyolithids, one of the two subgroups of hyoliths, consist of four elements including a conical conch, an external operculum, and a pair of curved enigmatic helens, but their ecology and internal morphology have long been considered controversial. Here we present for the first time, remarkably preserved hyolithids with helens and interior soft tissues from the Guanshan Biota (Cambrian, Stage 4) of Shijiangjun section, Wuding County in eastern Yunnan Province of South China. Preserved soft tissues and organs encompass the digestive tract, muscle scars and connective tissues between the operculum and conch. Three modes of soft part preservation in hyolithids from the Guanshan Biota are described: (1) preservation through pyritization, (2) sediment-infilling of guts, and (3) bacterial biofilm pseudomorphs (expressed as large internal hollow cavities), resulting from endogenous bacterial decay of soft parts. Such differential preservation of hyolith guts indicates different taphonomic modes for the soft parts of Cambrian animals in the Guanshan Biota. The newly collected material yields the oldest preserved guts in hyolithids from Konservat-biotas, and reveals new evidence for reconstructing hyolithid anatomy, such as the articulation mechanism of the opercula and the internal structures in the conch. Comparisons with younger wellpreserved hyolithid specimens indicate that the gut anatomy of hyolithids was evolutionarily conservative from the early Cambrian through to at least the Ordovician.