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  • 1.
    Arvestål, Emma
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Organic-walled microfossils in the Ediacaran of Estonia: Biodiversity on the East European Platform2020Inngår i: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 341, artikkel-id 105626Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Precambrian organic-walled microfossils are not only a source for studying evolution but also increasingly associated with stratigraphic correlation, based on key fossils and assemblage composition. For this reason, two drill cores from north-eastern Estonia have been studied for their content and stratigraphic distribution of organic-walled microfossils (OWM), analysing samples from the Precambrian Gdov, Kotlin, and Voronka formations. The recovered assemblages are generally well-preserved and diverse consisting of abundant sphaeromorphs, such as Leiosphaeridiaspp. and Pterospermopsimorpha spp., filamentous cyanobacteria, e.g. Cephalonyx geminatus and Palaeolyngbya catenata, and different types of cellular/colonial aggregates. In contrast, acanthomorphic acritarchs are rare with only a few unidentified examples present. The presence of taxa such as Pomoria rhomboidalisand Primoflagella speciosa in combination with the absence of large acanthomorphs suggests a late Ediacaran age of the studied samples. All in all, 38 species within 22 different genera are described herein, as are 9 taxa of unknown taxonomic affiliation. Another 11 taxa are briefly mentioned and depicted in order to provide for a better overview of the diversity of the assemblage. The stratigraphic distribution of the recognized taxa and assemblages can provide a powerful tool for correlation on the East European Platform as well as between Baltica and other palaeogeographic regions during the Ediacaran.

  • 2. Botting, Joseph P.
    et al.
    Muir, Lucy A.
    Pates, Stephen
    McCobb, Lucy M. E.
    Wallet, Elise
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Zhang, Yuandong
    Ma, Junye
    A Middle Ordovician Burgess Shale-type fauna from Castle Bank, Wales (UK)2023Inngår i: Nature Ecology & Evolution, E-ISSN 2397-334X, Vol. 7, nr 5, s. 666-674Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Burgess Shale-type faunas are critical to our understanding of animal evolution during the Cambrian, giving an unrivalled view of the morphology of ancient organisms and the ecology of the earliest animal-dominated communities. Rare examples in Lower Ordovician strata such as the Fezouata Biota illustrate the subsequent evolution of ecosystems but only from before the main phase of the Great Ordovician Biodiversification Event. Later Ordovician Konservat-Lagerstätten are not directly comparable with the Burgess Shale-type faunas as they do not represent diverse, open-shelf communities, limiting our ability to track ecological development through the critical Ordovician biodiversification interval. Here we present the Castle Bank fauna: a highly diverse Middle Ordovician Burgess Shale-type fauna from Wales (UK) that is directly comparable with the Burgess Shale and Chengjiang biotas in palaeoenvironment and preservational style. The deposit includes animals with morphologies similar to the iconic Cambrian taxa Opabinia, Yohoia and Wiwaxia, combined with early examples of more derived groups such as barnacles. Many taxa such as kinorhynchs show the small sizes typical of modern faunas, illustrating post-Cambrian miniaturization. Castle Bank provides a new perspective on early animal evolution, revealing the next chapter in ecosystem development following the Chengjiang, Burgess Shale and Fezouata biotas.

  • 3.
    Budd, Graham E.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Meidla, Tonu
    Univerity of Tartu.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Fossils & rocks: geotourism in the central Baltic2011Bok (Annet (populærvitenskap, debatt, mm))
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  • 4. Eliason, Sara
    et al.
    Bassett, Michael
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Geotourism highlights of Gotland2010Bok (Annet (populærvitenskap, debatt, mm))
    Fulltekst (pdf)
    Full PDF
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    Full iPad version
  • 5. Grey, Kathleen
    et al.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Taphonomy of Ediacaran acritarchs from Australia: significance for taxonomy and biostratigraphy2009Inngår i: Palaios, ISSN 0883-1351, E-ISSN 1938-5323, Vol. 24, nr 3-4, s. 239-256Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A diverse assemblage of Australian Ediacaran (late Neoproterozoic) acritarchs from the Centralian Superbasin and Adelaide Rift Complex demonstrates a range of taphonomic degradation. Recognition of taphonomic variants is critical for taxonomic studies and biostratigraphic interpretation. Taphonomic features observed include compression features, folding and tearing of vesicle walls, pitting, perforation, abrasion, exfoliation, shrinking, twisting, splitting, curling, shredding, pyritization, particle entrapment, and thermal maturation effects. The physical and chemical structure of the vesicle wall is instrumental in determining the degree of taphonomic damage. Consistent associations allow Identification of degradation series that incorporate previously described individual species and provide a framework for taxonomic revision. Taphonomic associations may also characterize taphofacies, providing an additional tool for basin analysis.

  • 6.
    Grey, Kathleen
    et al.
    Geological Survey of Western Australia, Department of Industry and Resources.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Paleobiologi.
    Moczydlowska, Malgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Paleobiologi.
    Calver, Clive
    Mineral Resources Tasmania, Australia.
    Hill, Andrew
    Australian Centre for Astrobiology, Department of Earth and Planetary Sciences, Macquarie University NSW.
    Neoproterozoic subdivision in Australia2005Inngår i: Central Australian Basins Symposium: Petroleum and Mineral Potential, 2005Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Neoproterozoic subdivision is well advanced in Australia using integrated results from lithostratigraphy, palynology, isotope chemostratigraphy and stromatolite biostratigraphy. Previously proposed Cryogenian correlations were tested by the drilling of GSWA Lancer-1 in the western Officer Basin and were found to be reliable. The consistency of the results allows the succession to be tied to limited geochronological ages from the Adelaide Rift Complex. Data are still sparse on the interval between the Sturtian and Marinoan glaciations, but good correlations exist in the Ediacaran.

    The base of the cap carbonate in Enorama Creek in the Adelaide Rift Complex has been ratified as the Global Stratotype Section and Point (GSSP) for the newly defined Ediacaran System and Period. The Flinders Ranges have a near-continuous section from the Marinoan glaciation to the Cambrian boundary, especially around the Brachina and Bunyeroo gorges. Lithostratigraphy, and local and regional correlations are well established, including links between the type sections, measured sections throughout the Adelaide Rift Complex and continuously cored drillhole sections on the Stuart Shelf, 80–100 km to the northeast, and to the Officer and Amadeus basins. An integrated approach, using lithostratigraphy; stratigraphic markers (glacial episodes, the time-synchronous Acraman impact ejecta layer, canyon cutting); carbon isotope chemostratigraphy; sequence stratigraphy; seismic interpretation; stromatolite biostratigraphy; and the first appearance of bilaterians and associated trace fossils, has proved successful.

    Acritarchs are acid-insoluble fossils of single-celled, phytoplanktonic green algae and are ideal for zonation. A rigorous sampling program began in 1991 to establish an acritarch biostratigraphy throughout Australian Neoproterozoic basins, based on palynological studies of continuously cored drillholes. Extensive field sampling of sections in the Flinders Ranges was unsuccessful, partly because the rift succession is too thermally mature for palynomorphs to be preserved, and partly because organic material has been leached from a deeply weathered profile. No identifiable acritarchs were recovered from this area, or from outcrops in other basins. However, Stuart Shelf drillholes contain well-preserved palynomorphs, although preservation is patchy in parts of the succession. Nevertheless, there are enough data for correlation with excellently preserved assemblages from the Officer and Amadeus basins. Georgina Basin preservation is too poor for useful analysis at present. Data from the Officer and Amadeus basins demonstrate the potential for biostratigraphic zonation in the lower and middle Ediacaran. Biostratigraphic correlation parallels correlations based on organic carbon isotope curves.

    Middle Ediacaran acritarch assemblages are extraordinarily diverse taxonomically, morphologically complex, and show typical patterns of secular diversity. These characteristics are ideal for the development of a zonal scheme, with levels of precision equivalent to the Phanerozoic record. The zones are independent of taphonomic and palaeoenvironmental influences, and they are demonstrably independent of lithology, lithostratigraphy, and sequence stratigraphy. Using composite sections, two palynofloras, the Ediacaran Leiosphere Palynoflora (ELP) and the Ediacaran Complex Acanthomorph Palynoflora (ECAP), have been recognised. The ECAP has been subdivided into four zones. The scheme is preliminary, but represents a significant advance in Neoproterozoic biostratigraphic studies, and should provide an important tool for future stratigraphic correlation. Additional studies are in progress to refine the correlations by examining undocumented parts of the succession, especially from Murnaroo-1 and Giles-1. The presence of certain acritarch species in probably coeval successions in Australia, Siberia, China, and northern Europe, suggests that the proposed zonation has good potential for global application, and that biostratigraphic principles and methodology can be applied to the Neoproterozoic.

  • 7.
    Grey, Kathleen
    et al.
    Geological Survey of Western Australia, Department of Industry and Resources.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Paleobiologi.
    Moczydlowska, Malgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Paleobiologi.
    Calver, Clive
    Mineral Resources Tasmania, Australia.
    Hill, Andrew
    Australian Centre for Astrobiology, Department of Earth and Planetary Sciences, Macquarie University NSW.
    Subdividing the Ediacaran of Australia using biostratigraphy2005Inngår i: Central Australian Basins Symposium: Petroleum and Mineral Potential, 2005Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A new Global Stratotype and Section (GSSP) for the terminal Neoproterozoic, the Ediacaran Period and System, has been ratified by the International Union of Geological Sciences (IUGS), but problems of subdivision and correlation remain. Hydrocarbon and mineral exploration in the Officer, Amadeus, and Georgina basins, and the Adelaide Rift Complex has resulted in the development of palynological (mainly acritarch) correlations using range charts, based on >1000 samples from >30 drillholes sampled about every 10 m. As in the Cryogenian, biostratigraphic correlations, based on palynology and stromatolite biostratigraphy, are feasible, and results are consistent with correlations based on carbon isotope curves established using splits of palynology samples.

    So far, zonation is only possible for the lower and middle Ediacaran in Australia. Upper Ediacaran lithologies are generally unsuitable for palynomorph preservation and assemblages appear to be highly impoverished. However, a distinctive assemblage of large acanthomorph acritarchs, with highly complex morphologies and short stratigraphic ranges, characterises the middle Ediacaran. They are ideal candidates for biostratigraphy and this interval can be correlated with a high degree of confidence. Assemblages from Baltica and the East European Platform suggest that palynological zonation of the upper Ediacaran may be possible, despite species reduction and a return to simple morphologies. Moreover, the upper Ediacaran contains the Ediacara fauna, which may also be a suitable tool for correlation.

    Stromatolites indicate Australia-wide correlation at certain levels of the Ediacaran. Incipient columns of Elleria minuta, characteristic of the Amadeus Basin (Marinoan-equivalent) cap dolomite, were identified in a 50 cm-thick dolomite horizon above a diamictite, in Empress-1/1A in Western Australia. Tungussia julia is widespread and appears to be facies independent. It occurs in shallow-water carbonates of the Julie Formation (Amadeus Basin), Wonoka Formation (Adelaide Rift Complex), Elkera Formation (Georgina Basin), and Wilari Dolomite Member of the Tanana Formation (eastern Officer Basin), and is present in the periglacial Egan Formation in the Kimberley area. Relative stratigraphy indicates that the Egan Formation is considerably younger than the Elatina Formation (Marinoan glaciation). The Egan glaciation took place at about 560 Ma, only a short time before the appearance of the first bilaterian trace fossils.

    Palynomorph assemblages are sparse during and between the Sturtian and Marinoan glaciations (~700–600 Ma) and samples immediately above the Marinoan glaciation are barren. Post-glacial benthic mats and leiospheres quickly re-established and flourished, as sea level and temperatures rose, but there is no obvious post-glacial species diversification, and no evidence of invasion by extremophiles from hot-spring refugia as envisaged in Snowball Earth predictions. Only a handful of species survived, but pre-glacial species appear to be identical to post-glacial species. Specimen numbers increased rapidly as sea-level rose, but so far, no new taxa have been identified below the Acraman impact ejecta layer.

    Above the Acraman impact layer, during a second sea-level rise, there is a striking change in the palynoflora, when >50 species of large acanthomorph acritarchs, belonging to several new genera, first appear and diversify rapidly. They differ significantly from older taxa and in some aspects resemble dinocysts. At least four zones have been recognised, based mainly on assemblages from continuous core in the eastern Officer Basin (Munta-1, Observatory Hill-1, Lake Maurice West-1, and Birksgate-1), the Adelaide Rift Complex succession (SCYW-1a, WWD-1 and MJ-1) and the Amadeus Basin (Wallara-1 and Rodinga-4). More detailed studies are in progress on distributions in Lake Maurice West-1, Observatory Hill-1, Murnaroo-1, and Giles-1. These drillholes are of particular significance because the precise position of the ejecta layer is known in each.

    Although the acanthomorph assemblage was recognised previously in Murnaroo-1, systematic sampling was not carried out and the position of the ejecta layer was not known. More refined sampling and the discovery of the ejecta layer at 279.55 m has now confirmed observations from other drillholes that the earliest appearance of the acanthomorphs is above the ejecta layer and that diversification was rapid, with 10 species already present, less than 50 m above the ejecta layer. Studies continue in an attempt to locate the earliest appearance of acanthomorphs. Preliminary examination of samples from Giles-1, where the ejecta layer was found at 554.90 m, confirms the acritarch distribution pattern. Stable isotope studies are also providing significant data about the effect of the Acraman impact on the biosphere.

    Several key acanthomorph species are present elsewhere in the world, including Svalbard, Norway, Siberia, and China, raising the possibility of global correlation. In particular, the Australian assemblage has several taxa in common with a succession in an area in eastern Siberia that contains one of the giant Neoproterozoic gas fields. Further work is required to define the ranges of key species outside Australia, so the scheme can be extended globally.

    At present, contradictions arise when correlations are attempted with the Doushantuo Formation in China. In part, this reflects the lack of methodical stratigraphic sampling in the Chinese succession and the disparity in thickness between the Chinese succession (<200 m) and the Australian succession (>2000 m). There are also discrepancies in the acritarch biostratigraphy and carbon isotope curves that raise issues about whether the Nantuo Tillite should be correlated with the type ‘Marinoan’ glaciation, the Elatina Formation, and these discrepancies have implications about how many glacial episodes happened in the Neoproterozoic. Recent dating on probable equivalents of the Elatina Formation in King Island and Tasmania suggest an age of 580 Ma. This is similar to the age of the Gaskiers and Squantum Tillites in western Canada, but considerably younger than recently obtained ages of 635 Ma on successions in southern Africa and the Nantuo Tillite in China.

    Prospects for subdividing and correlating the Ediacaran using biostratigraphy are excellent, provided taxonomic ranges are properly documented. Biostratigraphic subdivisions can be integrated with other means of correlation to provide a rigorous means of global correlation.

  • 8.
    Huld, Sigrid
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    McMahon, Sean
    Neubeck, Anna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Experimental mineralisation in carbonate, phosphate, and silicate of the filamentous hydrogenotrophic methanogen Methanobacterium oryzae Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Methanogens are thought to be some of the most ancient organisms to have lived on Earth. Fossils of ancient mineralised filamentous forms have been described before from hydrothermal vents to sediments. The peculiarity of Archaea lies in their cell walls, where they lack the peptidoglycan layer found in Bacteria and instead have a proteinaceous S-layer that has been shown to promote mineralisation through the presence of charged polymers on the cell surface. Some methanogens, like the filamentous Methanobacterium oryzae do not have an S-layer but a cell wall made of pseudomurein, similar in structure to bacterial murein. In this work, experimental mineralisation with carbonate, phosphate, and silica on a strain of M. oryzae were analysed. Differences in the degree of morphological preservation in the various fossilisation agents were observed over a period of 3 months and chemical analyses using EDX and XRD were carried out on precipitates. Results indicate that the various minerals precipitate differently in association with the methanogens and only silica replicates the morphology with a relatively high degree of fidelity. This shows the presence of possible taphonomic biases in the rock record depending on mineralisation, size differences, and cell wall structure. Therefore, this work has important outcomes for the recognition of filamentous fossils in the rock record and on the different mineralisation mechanisms on early Earth.

  • 9.
    Moczydlowska, Malgorzata
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Pease, Victoria
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Wickström, Linda
    Agić, Heda
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    A Tonian age for the Visingsö Group in Sweden constrained by detrital zircon dating and biochronology: implications for evolutionary events2018Inngår i: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 155, nr 5, s. 1175-1189Artikkel i tidsskrift (Fagfellevurdert)
  • 10.
    Moczydlowska, Malgorzata
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Ultrastructure of cell walls in ancient microfossils as a proxy to their biological affinities2009Inngår i: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 173, nr 1-4, s. 27-38Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Bacteria and protoctists dominated the biosphere in the Archean and Proterozoic, their affinities being deduced by studies of their comparative morphology, palaeoecology, biogeochemistry, and wall ultrastructure. However, exact phylogenetic relationships are uncertain for most such microfossils. Because of the limitations imposed by the simple morphology and small dimensions of such microorganisms and their little known biochemistry, new techniques in microscopy, tomography and spectroscopy are applied to examine individual microfossils at the highest attainable spatial resolution. TEM/SEM studies of the wall ultrastructure of sphaero- and acanthomorphic acritarchs have revealed complex, single to multilayered walls, having a unique texture in sub-layers and an occasionally preserved trilaminar sheath structure (TLS) of the external layer. A variety of optical characteristics, the electron density and texture of fabrics of discrete layers, and the properties of biopolymers may indicate the polyphyletic affiliations of such microfossils and/or the preservation of various stages (vegetative, resting) in their life cycle. Primarily, wall ultrastructure allows discrimination between fossilized prokaryotic and eukaryotic cells. Composite wall ultrastructure provides evidence that some Proterozoic and Cambrian leiosphaerids are of algal affinities (but not, per se, that they are referable to "Leiosphaeridia"). Certain Cambrian specimens represent chlorophyceaens, having the multilayered composite wall with TLS structure known from vegetative and resting cells in modern genera of the Chlorococcales and Volvocales. The wall ultrastructure of the studied Cambrian and Proterozoic acanthomorphs resembles the resting cysts of green microalgae, but there is no evidence to suggest a close relationship of these taxa, to dinoflagellates. It is apparent that although there is no single and direct method to recognize the precise phylogenetic relations of such microfossils, ultrastructural studies of their preserved cell walls and encompassing sheaths, combined with biochemical analyses and other advanced methods, may further elucidate their affinities to the modern biota.

  • 11.
    Moczydlowska-Vidal, Malgorzata
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Schopf, James William
    University of California, Los Angeles, Department of Earth and Space Sciences.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Micro- and nano-scale ultrastructure of cell walls in Cryogenian microfossils: revealing their biological affinity2010Inngår i: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, Vol. 43, nr 2, s. 129-136Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recently established protocols and methods in advanced microscopy and spectrometry applied to studies of ancient unicellular organic-walled microfossils of uncertain biological affinities (acritarchs) provide new evidence of the fine ultrastructure of cell walls and their biochemistry that support the interpretation of some such microfossils as photosynthesizing microalgae. The micro-scale and nanoscale ultrastructure of the cell walls of late Cryogenian sphaeromorphic acritarchs from the Chichkan Formation (Kazakhstan) revealed by the advanced techniques and studied originally by Kempe et al. (2005) is here further analyzed and compared to that of modern microalgal analogues. On the basis of such comparison, we interpret the preserved cell wall ultrastructure to reflect original layering and lamination within sublayers of the fossil wall, rather than being a result of taphonomic and diagenetic alteration. The outer thick layer represents the primary wall and the inner layer the secondary wall of the cell, whereas the laminated amorphous sub-layers, 10-20 nm in thickness and revealed by transmission electron and atomic force microscopy, are recognized as trilaminar sheath structure (TLS). Because two-layered cell walls, trilaminar sheaths, and the position of the TLS within the fossil cell wall are characteristic of the mature developmental state in cyst morphogenesis in modern microalgae, we infer that the Chichkan sphaeromorphs are likely resting cells (aplanospores) of chlorophyceaen green microalgae from the Order Volvocales.

  • 12.
    Moczydlowska-Vidal, Malgorzata
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Paleobiologi.
    Leiming, Yin
    Life cycle of Early Ordovician acritarch species2003Konferansepaper (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    Acritarchs are marine planktonic autotrophic protistans of heterogeneous origins. Their diversification into many morphotypes occurred throughout Neoproterozic and Early Palaeozoic; some morphotypes represent green algal classes but most are of unknown biological affinities. Palaeobiology and relationships to extant microbiota of some acritarchs, with emphasis on their life cycle, reproduction and environmental adaptations, may be inferred from phonetic morphological features and cell wall ultrastucture. Microfossils from the Cambrian-Ordovician of China are studied to reveal the wall ultrastructure of vegetative cells and dormant/reproductive cysts, the structural complexity of early eukaryotic cytoskeleton, and to recognize by morphological and ultrastructural means the relationships between various phenotypes. Acritarchs are considered to be preservable cysts of unicellular algae. The new discovery of the entire organism consisting of vegetative envelope and internal cyst shows that some taxa indeed represent the dormant/reproductive cysts whereas other may represent vegetative cells in their complex life cycle. Formation of the cyst, the excystment structure (pylome) and change of the generations (sexual and asexual) in the life cycle of unicellular microbiota may shed light on the development of the early adaptations to survive ecological crises events and as a competitive advantage in increasingly complex marine ecosystems.

  • 13. Olcott-Marshall, Alison
    et al.
    Marshall, Craig
    Mozcydlowska, Malgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Multiple lines of chemical evidence for pelagic Neoproterozoic acritarchs2009Inngår i: Abstract Volume  international conference on the Cambrian explosion Walcott 2009, 2009, s. 47-Konferansepaper (Annet vitenskapelig)
  • 14.
    Peel, John Stuart
    et al.
    Uppsala universitet, Enheten för musik och museer, Evolutionsmuseet. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Cavity-dwelling microorganisms from the Ediacaran and Cambrian of North Greenland (Laurentia)2022Inngår i: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 96, nr 2, s. 243-255, artikkel-id PII S0022336021000962Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Records of diagenetically mineralized, filamentous, cavity-dwelling microorganisms extend back to strata from the early Paleoproterozoic (2400 Ma). In North Greenland (Laurentia), they are first known from the Ediacaran (Neoproterozoic; ca. 600 Ma) Portfjeld Formation of southern Peary Land, in association with a biota similar to that of the Doushantuo Formation of China. The Portfjeld Formation cavity dwellers are compared with more widespread occurrences in Cambrian (Series 2, Stage 4, Miaolingian Series) strata from the same region in which assemblages in postmortal shelter structures within articulated acrotretoid brachiopods and other invertebrates are common. All specimens were recovered by digestion of carbonate samples in weak acids. The described fossils are preserved as mineral encrusted threads but this diagenetic phosphatization unfortunately obscures their biological identity.

  • 15.
    Peel, John Stuart
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    THE BUEN FORMATION (CAMBRIAN SERIES 2) BIOTA OF NORTH GREENLAND2018Inngår i: Papers in Palaeontology, ISSN 2056-2799, E-ISSN 2056-2802, Vol. 4, nr 3, s. 381-432Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The diverse metazoan fauna from the upper member of the Buen Formation of North Greenland is described as a complement to published descriptions of the exceptionally preserved fauna of the Sirius Passet Lagerstatte which occurs in the lowest beds of the formation. Considered together with organic-walled microfossils, which are absent from the Sirius Passet Lagerstatte on account of regional metamorphism, the fauna from the upper member provides an extended picture of the Buen Formation biota (Cambrian, Series 2, Stages 3-4; Montezuman-Dyeran of Laurentian usage). Although dominated numerically by specimens of the olenelline trilobites Limniphacos and Mesolenellus, the oldest assemblages (Montezuma-Dyeran boundary) from the upper member of the Buen Formation are characterized by a high diversity of hyoliths which often occur as partial associations of conch, operculum and helens in the dark mudstones; hyoliths are rare in the Sirius Passet Lagerstatte. Sponges are rare in the upper Buen Formation but diverse at Sirius Passet. Unlike the Sirius Passet Lagerstatte, fossil remains of non-mineralized metazoans with limbs and other details of internal anatomy do not occur in the upper Buen Formation, although organic tubes assigned to a new selkirkiid stem group priapulid (Sullulika) are common. New taxa: Alutella siku sp. nov., Sullulika broenlundi gen. et sp. nov., Nevadotheca boerglumensis sp. nov., Kalaallitia myliuserichseni gen. et sp. nov., Nasaaraqia hyptiotheciformis gen. et sp. nov., Trapezovitus malinkyi sp. nov., Decoritheca? hageni sp. nov.

  • 16.
    Peel, John Stuart
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Hageman, Steven J.
    Appalachian State Univ, Dept Geol & Environm Sci, Boone, NC 28608 USA..
    The oldest hyolithids (Cambrian Series 2, Montezuman Stage) from the Iapetan margin of Laurentia2020Inngår i: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 94, nr 4, s. 616-623Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The recent description of the nevadioid trilobiteBuenellus chilhoweensisWebster and Hageman,2018established the presence of early Cambrian Montezuman Stage (Cambrian Series 2, Stage 3) faunas in the Murray Shale of Chilhowee Mountain, Tennessee. The description recognized the oldest known age-diagnostic Cambrian trilobite from the Laurentian margin of the former Iapetus Ocean sinceBuenellusBlaker, 1988 is known otherwise only from the Sirius Passet Lagerstatte on the Innuitian margin of North Greenland. The bivalved arthropodsIsoxys chilhoweanusWalcott,1890andIndota tennesseensis(Resser,1938a) have also been described from the Murray Shale, but hyolithids appear to be the dominant body fossils in terms of diversity and abundance. Although poorly preserved, the hyolithids occurring together withBuenellus chilhoweensisare described to improve understanding of the Murray Shale biota. The hyolith assemblages of the Murray Shale and Sirius Passet Lagerstatte are not closely similar, although the poor preservation of both hinders comparison.

    Fulltekst (pdf)
    FULLTEXT01
  • 17.
    Peel, John Stuart
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Schack Pedersen, Stig
    Geological Survey of Denmark and GreenlandCopenhagen KDenmark.
    Unusual preservation of an Ordovician (Floian) arthropod from Peary Land, North Greenland (Laurentia)2020Inngår i: Palaeontologische Zeitschrift, ISSN 0031-0220, E-ISSN 1867-6812, Vol. 94, nr 1, s. 41-51Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Preservation of a fragment of an arthropod from starved trough sediments of the Bøggild Fjord Formation (Ordovician, Floian) of Johannes V. Jensen Land in north Peary Land, North Greenland, recalls that of the lower Cambrian Sirius Passet Lagerstätte of extreme north-west Peary Land and may suggest a second locality for exceptional preservation in North Greenland. A prominent petaloid pattern on the tergopleurae reflects impression onto the internal mould of terrace lines from the cuticle exterior. The arthropod is associated with poorly preserved sponges and a depauperate assemblage of organic-walled microfossils. It is tentatively compared to Mollisonia, originally described from the Burgess Shale Lagerstätte (middle Cambrian, Miaolingian Series) of Canada.

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  • 18. Puurmann, Elle
    et al.
    Ratas, Urve
    Raukas, Anto
    Bauert, Heikki
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Geotourism highlights of the Estonian small islands2010Bok (Annet (populærvitenskap, debatt, mm))
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  • 19. Raukas, Anto
    et al.
    Bauert, Heikki
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Puurmann, Elle
    Ratas, Urve
    Geotourism highlights of the Saaremaa and Hiiumaa islands2009Bok (Annet (populærvitenskap, debatt, mm))
    Fulltekst (pdf)
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    Fulltekst (epub)
    Full iPad version
  • 20.
    Slater, Ben
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Harvey, Thomas
    Guilbaud, Romain
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Budd, Graham
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Butterfield, Nicholas J.
    The Ediacaran–Cambrian transition: the emerging record from Small Carbonaceous Fossils (SCFs)2019Inngår i: Estudios Geologicos, ISSN 0367-0449, E-ISSN 1988-3250, Vol. 75, nr 2, s. 38-40Artikkel i tidsskrift (Fagfellevurdert)
    Fulltekst (pdf)
    fulltext
  • 21.
    Slater, Ben
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Early Cambrian small carbonaceous fossils (SCFs) from an impact crater in western Finland2019Inngår i: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, Vol. 52, nr 4, s. 570-582Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We describe an assemblage of small carbonaceous fossils (SCFs) and acritarchs from cored siltstones of the Lappajärvi impact structure, west‐central Finland. Previous studies had detected a depauperate acritarch biota ascribed to a deep Proterozoic origin—this age, however, was based on recovery of long‐ranging poorly age‐diagnostic sphaeromorphs. To resolve the age and provenance of these crater sediments, we applied low‐manipulation processing techniques optimized for retrieval of larger organic‐walled microfossils. Our study revealed a previously undetected assemblage containing numerous metazoan SCFs consisting of flattened ‘protoconodonts’ (grasping spines assignable to total group Chaetognatha) and a distinctive fossilised chaeta, possibly representing the oldest known annelid remains. Phylogenetically problematic fossils include various acritarchs (large Leiosphaeridia sp., Tasmanites tenellus, smaller sphaeromorphs, Synsphaeridium, Archaeodiscina and Granomarginata) and filamentous forms (Palaeolyngbya‐ and Rugosoopsis‐like filaments, Siphonophycus), likely representing prokaryotic or protistan grades of organisation. As well as adding new diversity to an emerging SCFs record, these data substantially refine the age of these sediments by more than half a billion years, to an early Cambrian Terreneuvian age. More specifically, the assemblage is equivalent to that of the Lontova Formation from the Baltic States and northwest Russia, but is previously unreported from Finland. Identification of Lontova‐type SCFs/organic‐walled microfossils at Lappajärvi further constrains the poorly resolved extent of maximum flooding during the early Cambrian in Baltica. Renewed attention should be directed to strata that have thus far produced only biostratigraphically long‐ranging or ambiguous palynological assemblages—‘SCF‐style’ processing can reveal hitherto undetected, age‐informative microfossils that are otherwise selectively removed in conventional palynological studies.

  • 22.
    Slater, Ben
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Budd, Graham E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Peel, John Stuart
    Uppsala universitet, Enheten för musik och museer, Evolutionsmuseet. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Widespread preservation of small carbonaceous fossils (SCFs) in the early Cambrian of North Greenland2018Inngår i: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 46, nr 2, s. 107-110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The early Cambrian (ca. 518 Ma) Sirius Passet Lagerstätte of North Greenland is one of the most celebrated sites bearing fossils of soft-bodied organisms, and provides key insights into the Cambrian explosion of animal life. Unlike the younger Burgess Shale (508 Ma), the Sirius Passet biota does not preserve original carbonaceous material because of its history of metamorphic heating. Nearby sediments from within the same formation, however, have escaped the worst effects of thermal alteration. We report an entirely new diversity of metazoan remains preserved in a Burgess Shale–type fashion from sediments throughout the Buen Formation, in the form of small carbonaceous fossils (SCFs). The assemblages include the oldest known pterobranch hemichordates, diverse cuticular spines of scalidophoran worms, demineralized trilobite cuticle, bivalved arthropods (Spinospitella-like and Isoxys-like forms), protoconodonts, and a variety of less phylogenetically constrained metazoan and protistan forms. Together these SCFs capture exceptional microanatomical details of early Cambrian metazoans and offer new insights into taphonomic pathways at Sirius Passet and the nature of Burgess Shale–type preservation.

  • 23. Tuuling, Igor
    et al.
    Bauert, Heikki
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Budd, Graham
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    The Baltic Sea: Geology and geotourism highlights2011Bok (Annet (populærvitenskap, debatt, mm))
    Fulltekst (pdf)
    fulltext
  • 24.
    Wallet, Elise
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Slater, Ben
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Morphometric analysis of Skiagia-plexus acritarchs from the early Cambrian of North Greenland: toward a meaningful evaluation of phenotypic plasticity.2022Inngår i: Paleobiology, ISSN 0094-8373, E-ISSN 1938-5331, Vol. 48, nr 4, s. 576-600Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Cambrian evolutionary radiations are marked by spectacular biotic  turnovers and the establishment of increasingly tiered food chains. At  the base of these food chains are primary producers, which in the  Cambrian fossil record are chiefly represented among organic-walled  microfossils. The majority of these microfossil remains have  traditionally been attributed to an informal category of incertae sedis  called “acritarchs,” based entirely on form taxonomy. Acritarch form  taxa have been intensely used for biostratigraphy and in large-scale  studies of phytoplankton diversity. However, both prospects have been  challenged by cases of taxonomic inconsistencies and oversplitting  arising from the large phenotypic plasticity seen among these  microfossils. The acritarch form genus Skiagia  stands as an ideal case study to explore these taxonomic challenges,  because it encompasses a number of form species widely used in lower  Cambrian biostratigraphy. Moreover, subtle morphological differences  among Skiagia species were suggested to  underlie key evolutionary innovations toward complex reproductive  strategies. Here we apply a multivariate morphometric approach to investigate the morphological variation of Skiagia-plexus  acritarchs using an assemblage sourced from the Buen Formation  (Cambrian Series 2, Stages 3–4) of North Greenland. Our analysis showed  that the species-level classification of Skiagia  discretizes a continuous spectrum of morphologies. While these findings  bring important taxonomic and biostratigraphic hurdles to light, the  unequal frequency distribution of life cycle stages among Skiagia species suggests that certain elements of phytoplankton paleobiology are nonetheless captured by Skiagia  form taxonomy. These results demonstrate the value of using  morphometric tools to explore acritarch phenotypic plasticity and its  potential ontogenetic and paleoecological drivers in Cambrian  ecosystems.

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  • 25.
    Wallet, Elise
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Slater, Ben
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Organic-walled microfossils from the early Cambrian of North Greenland: a reappraisal of diversityManuskript (preprint) (Annet vitenskapelig)
  • 26.
    Wallet, Elise
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Slater, Ben
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Organic-walled microfossils from the lower Cambrian of North Greenland: a reappraisal of diversity2023Inngår i: Palynology, ISSN 0191-6122, E-ISSN 1558-9188, Vol. 47, nr 4, artikkel-id 2251044Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The early Cambrian Buen Formation (North Greenland) hosts an exceptionally rich fossil biota that has contributed significantly to our knowledge of early metazoans, yet the fossil remains of primary producers from this deposit have received less attention. Here we examine the palynological component of the Buen Formation, with a focus on acritarchs and filamentous microfossils. Our analysis revealed the presence of 49 form taxa, 15 of which are described for the first time in the Buen Formation. These include large elements of presumably benthic origin, together with cyst-like acritarchs. Comasphaeridium longispinosum Vidal 1993 is renamed Comasphaeridium? brillesensis nom. nov., and Comasphaeridium densispinosum Vidal 1993 is reassigned to a new genus, Pearisphaeridium, becoming Pearisphaeridium densispinosum comb. nov. The diagnoses of Pearisphaeridium densispinosum (Vidal 1993) comb. nov. and Skiagia pura Moczydlowska 1988 are emended. Further, careful analysis of disparity in the recovered assemblage has revealed the presence of numerous transitional morphologies among the recorded acritarch form taxa. Though some of these transitional forms likely represent biologically meaningful entities (e.g. life cycle stages, ecophenotypes), others appear to have been artificially generated by taphonomic processes. Accounting for taphonomic factors and other sources of morphological variation has curtailed diversity down to 30 acritarch morphotypes, ten of which represent distinct abundance peaks broadly corresponding to acritarch genera. This analysis illustrates how population-based studies of early Cambrian acritarchs can help to discern the different factors that impinge on acritarch morphology, detect instances of taxonomic inflation, and refine our measures of diversity at the base of early Palaeozoic food webs.

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  • 27.
    Wallet, Elise
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Slater, Ben
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    The palaeobiological significance of clustering in acritarchs: a case study from the early Cambrian of North Greenland Manuskript (preprint) (Annet vitenskapelig)
  • 28.
    Wallet, Elise
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Slater, Ben
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Peel, John Stuart
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Small carbonaceous fossils (SCFs) from North Greenland: new light on metazoan diversity in early Cambrian shelf environments2021Inngår i: Papers in Palaeontology, ISSN 2056-2799, E-ISSN 2056-2802, Vol. 7, nr 3, s. 1403-1433Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Sirius Passet Lagerstätte of North Greenland is one of the oldest records of soft-bodied metazoan-dominated ecosystems from the early Cambrian. The Lagerstätte site itself is restricted to just a single c.a. 1-km-long outcrop located offshore from the shelf margin, in an area affected by metamorphic alteration during the Ellesmerian Orogeny (Devonian–Early Carboniferous). The recent recovery of small carbonaceous fossils (SCFs) to the south, in areas that escaped the effects of this deformation, has substantially expanded the known coverage of organic preservation into shallower water depositional settings in this region. Here, we describe additional SCF assemblages from the siliciclastic shelf succession of the Buen Formation (Cambrian Series 2, stages 3–4; c.a. 515 Ma), expanding the previously documented SCF biota. Newly recovered material indicates a rich diversity of non-mineralizing metazoans, chiefly represented by arthropod remains. These include the filtering and grinding elements of a sophisticated crustacean feeding apparatus (the oldest crustacean remains reported to date), alongside an assortment of bradoriid sclerites, including almost complete, 3D valves, which tie together a number of SCFs previously found in isolation. Other metazoan remains include various trilobite cuticles, diverse scalidophoran sclerites, and a range of metazoan fragments of uncertain affinity. This shallower water assemblage differs substantially from the Sirius Passet biota, which is dominated by problematic euarthropod stem-group members and sponges. Although some of these discrepancies are attributable to taphonomic or temporal factors, these lateral variations in taxonomic composition also point to significant palaeoenvironmental and/or palaeoecological controls on early Cambrian metazoan communities.

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  • 29.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Acritarch data from Australian Neoproterozoic successions2010Konferansepaper (Annet vitenskapelig)
  • 30.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. paleobiologi.
    Acritarchs - the solution for Ediacaran biostratigraphy?2007Inngår i: Cimp Lisbon ´07: Joint meeting of spores/pollen and Achritarch subcomissions, 2007Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 31.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Acritarchs and their potential in Ediacaran biostratigraphy – Examples from the Officer Basin, Australia2007Inngår i: Comunicações Geológicas, nr 94, s. 81-92Artikkel i tidsskrift (Fagfellevurdert)
  • 32.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Paleobiologi.
    Life in the Ediacaran - A study of organic walled microfossils from Australia2006Licentiatavhandling, monografi (Annet vitenskapelig)
  • 33.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Morphology and wall ultrastructure of leiosphaeric and acanthomorphic acritarchs from the Ediacaran of Australia2009Inngår i: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 7, nr 1, s. 8-20Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Acritarchs are a group of organic-walled microfossils with unknown biological affinities. The wall ultrastructure of the unornamented, smooth Leiosphaeridia sp. and the acanthomorphic Gyalosphaeridium pulchrum from the Ediacaran Dey Dey Mudstone in the Officer Basin, South Australia, was studied by use of transmission and scanning electron microscopy, and transmitted light microscopy. The study of the ultrastructure reveals a complexity in the cell wall not seen in prokaryotes. Wall ultrastructures range from single-layered to three- or four-layered and from homogeneous to porous. Acritarchs with different wall ultrastructures may be different organisms, but may also reflect different stages in a life cycle. In this paper I review previous ultrastructure studies and discuss possible algal and metazoan affinities for the specimens studied herein.

    Fulltekst (pdf)
    FULLTEXT01
  • 34.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Paleobiologi.
    Neoproterozoic (Ediacaran) radiation of acritarchs – a new record2004Inngår i: Polen: XI International palyonological congress 2004, 2004, s. 601-Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The terminal Neoproterozoic radiation of planktonic photosynthetic microbiota (acritarchs) is one of the most significant evolutionary events of the time, including diversification of prokaryotic cyanobacteria and eukaryotic green and brown algae, the appearance of thecoamoebaens and subsequently metazoans (the Ediacara fauna). The Ediacaran radiation of phytoplankton is recognizable by the first appearance of more than fifty new species of large ornamented acritarchs in a short interval of time at ca. 570 Ma. This radiation event occurred after the Snowball Earth conditions returned to a kind of "normal" environmental stasis, and it may be interpreted as a recovery diversification of phytoplankton after a major biotic extinction caused by the global glaciation.

    The appearance of numerous, morphologically innovative and large acritarch taxa may also be connected with the Acraman impact event in South Australia, suggested recently by Grey et al. (2003), as a biotic recovery after the catastrophic environmental disturbance caused by the giant bolide. The latter hypothesis has to be tested, however, because a few individual taxa of ornamented acritarchs may have actually appeared below the ejecta layer, which is difficult to recognize with certainty in some borehole successions.

    The Ediacaran acritarch records are from Australia (the Officer and Amadeus Basins), China and Siberia, showing a worldwide distribution in a relatively short interval of time (ca. 20 Ma; Grey, 2004, in press). The greatest taxonomic diversity is known from Australia (ibidem), and the present study is focused on the investigation of Ediacaran microbiota in greater detail and from different stratigraphic levels, their palaeobiology and affinities, mode of life and reproduction cycle. The new assemblage of organic-walled microfossils from the Murnaroo 1 borehole comprises filamentous cyanobacteria, and ornamented and spheroidal acritarchs.

    The Ediacaran successions in Australia have been well documented in terms of lithostratigraphy, depositional settings and structural geology. The sedimentation proceeded in two different depositional regimes, recognized today in a series of sub-basins. One of them is the Officer Basin, comprised of complex intracratonic, east-west trending troughs and sub-basins extending from Western Australia to South Australia. The studied Murnaroo 1 borehole is also located there. The sediments accumulated in tidal, sub- and intertidal shelf conditions, and the predominantly mudstone lithology from which the samples were collected, is ideal for palynological processing and preservation of microfossils. The lack of macrofossils in the successions rendered efforts and advances in acritarch biostratigraphy since the 1980's, which helped to reveal a complex history of the Officer Basin. The discovery of two distinct palynofloras, an older leiosphere-dominated flora (ELP) and a younger acanthomorph-dominated flora (ECAP), is suggested to be largely environmentally independent (Grey, 2004, in press) in terms of the observed lithology and sedimentological sequences. However, the possible coupling between the Marinoan glaciation, the Acraman impact and the radical change in the palynofloras was inferred (ibidem) and this will be examined with the new data available from the Murnaroo 1 borehole. Previously, the Murnaroo succession was only studied preliminarily.

    In my communication, I will discuss the stratigraphic sequence of appearances of various species and their relationship to the environmental conditions, the Acraman impact event and the changes associated with the global glaciations.

    GREY, K., WALTER, M.R. and CALVER, C.R. (2003) Neoproterozoic biotic diversification: "Snowball Earth" or aftermath of the Acraman impact? Geology 31, p. 459-462.

    GREY, K., (2004, in press) Ediacarian Palynology of Australia. Australasian Association of Palaeontologists, Memoirs.

  • 35.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Revealing acritarch affinities by use of transmission electron micrsoscopy2007Inngår i: 51st Palaeontological Association Annual Meeting, Programme with abstracts, 2007Konferansepaper (Annet vitenskapelig)
  • 36.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Paleobiologi.
    SUBDIVIDING THE EDIACARAN SYSTEM IN AUSTRALIA USING ACRITARCHS2005Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The terminal Neoproterozoic was a period of time in Earth history that was characterised by severe environmental turbulence. At least two major, global glaciations between ca. 700-580 Ma might have acted as evolutionary bottlenecks that led to a rapid diversification of several lineages of single celled and, eventually, multicellular organisms. A large bolide impact in present day southern Australia at around 580 Ma could also have affected the evolution and diversification of microphytoplankton, at least on a local scale (Grey et al. 2003). The appearance of more than 50 ornamented acritarchs above the impact ejecta layer provides an excellent potential for these organisms to be used in biostratigraphy.

    The Ediacaran System is defined by its lower boundary occurring between the glacial deposits from the last major glaciation, the Marinoan glaciation, and the overlying cap carbonate, and by the base of the Cambrian System. This system is not very well known and in terms of fossil studies it is just in its infancy. Palynomorph assemblages containing organic walled microfossils, mainly acritarchs and prokaryotic organisms, are recovered from numerous drillholes located in southern Australia. Preliminary studies of a large number of acritarch samples from more than 30 drillcores (Grey 2005) have resulted in a subdivision of the middle Ediacaran into biozones based on the first appearance of index species and characteristic assemblages. Additional studies of drillcores from the Officer Basin in Australia will aid in the correlation between different basins in Australia and hopefully also global correlation. The studies of the Murnaroo 1 succession indicate a consistency with the previously examined boreholes and allow more accurate recognition of the acritarch biozones.

    Grey, K., Walter, M.R. & Calver C.R., 2003: Neoproterozoic biotic diversification: Snowball Earth or aftermath of the Acraman impact? Geology, v. 31.

    Grey, K., 2005, in press: Ediacaran Palynology of Australia. Australasian Association of Palaeontologists, Memoirs, v. 31.

  • 37.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Testing the role of spines as predatory defense2007Inngår i: Journal of Shellfish Research, ISSN 0730-8000, E-ISSN 1943-6319, Vol. 26, nr 1, s. 261-266Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spines are frequently considered to be an important physical defense against predators. This experiment shows that spines do not always function successfully as physical protection. Using natural predators and prey (the drilling muricid gastropod Nucella lamellosa (Gmelin 1791) and the mussel Mytilus trossulus (Gould 1850)) this experiment used artificial spines in different configurations and densities to try to assess the role of spines as predatory defense. The presence of spines did not inhibit the predator from choosing ornamented prey. Greater spine density did not improve the probability of surviving a predator encounter. Although mean handling time increased to some extent with higher spine density, the outcome of the encounter was the same. Presence or density of spines did not deter predators from attacking prey, and experimental prey with greater spine-density experienced greater mortality than did specimens with fewer spines. Drillhole dimensions differed slightly between the treatments, probably as a consequence of difficulties for the gastropod to maneuver its accessory boring organ (ABO) in between the spines.

  • 38.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    The Ediacaran Diversification of Organic-walled Microbiota: Ocean Life 600 Million Years Ago2008Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The only direct evidence of past life is provided by fossils. Fossils tell us about the evolution of life on Earth and they give us clues concerning ancient environments. The Ediacaran Period (roughly 635-542 million years ago) is characterised by the appearance and diversification of various microbiota and also the diversification of metazoans. Well-preserved organic-walled microfossils referred to as acritarchs occur abundantly in Ediacaran sedimentary successions in the Officer Basin in South Australia. Acritarch assemblages from the Giles 1 and Murnaroo 1 drillcores show a wide morphological disparity and are taxonomically diverse. Assemblages change over short stratigraphic intervals which enables the recognition of different biozones. The presence of taxa common between Australia, Siberia, Baltica and China provides a means for global correlation of the Ediacaran System. Examination of the wall ultrastructure of several acritarch specimens by use of transmission electron microscopy reveals a complexity in the cell wall that is not seen in prokaryotes but is indicative in some cases of particular clades of microalgae. Wall ultrastructures range from single-layered to three- and four-layered and from homogeneous to porous. The wall ultrastructure can be used to assess biological affinities and the affinities of the studied taxa in relation to green algae, dinoflagellates and metazoans are discussed. However, before taxonomic interpretations can be made with confidence, an understanding of taphonomic degradation of microorganisms is required. With focus on illustrated specimens, one part of this thesis explains what happens to an acritarch as it undergoes various types of degradation and why an understanding of these processes is important for taxonomic identification. A meteorite impact in South Australia spread an ejecta layer over a 550 km radius area. This ejecta layer is recognised in subsurface drillcores and provides an independent stratigraphic marker horizon that supports an acritarch-based correlation.

    Delarbeid
    1. Neoproterozoic (Ediacaran) diversification of acritarchs – A new record from the Murnaroo 1 drillcore, eastern Officer Basin, Australia.
    Åpne denne publikasjonen i ny fane eller vindu >>Neoproterozoic (Ediacaran) diversification of acritarchs – A new record from the Murnaroo 1 drillcore, eastern Officer Basin, Australia.
    2006 Inngår i: Review of Palaeobotany and Palynology, Vol. 139, nr 1-4, s. 17-39Artikkel i tidsskrift (Fagfellevurdert) Published
    Identifikatorer
    urn:nbn:se:uu:diva-97147 (URN)
    Tilgjengelig fra: 2008-04-15 Laget: 2008-04-15bibliografisk kontrollert
    2. Ediacaran acritarch biota from the Giles 1 drillhole, Officer Basin, Australia, and its potential for biostratigraphic correlation
    Åpne denne publikasjonen i ny fane eller vindu >>Ediacaran acritarch biota from the Giles 1 drillhole, Officer Basin, Australia, and its potential for biostratigraphic correlation
    2008 (engelsk)Inngår i: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 162, nr 3-4, s. 498-530Artikkel, forskningsoversikt (Fagfellevurdert) Published
    Abstract [en]

    The remarkable diversification of single-celled photosynthesising biota of algal and other as yet unknown affinities (acritarchs), followed by the diversification of metazoans, occurred during the Ediacaran Period, which is marked by extreme climatic and environmental changes. Here we describe a taxonomically diverse acritarch association from the Ediacaran part of the Giles 1 drillcore in the Officer Basin, South Australia, which documents further the Ediacaran phytoplankton radiation. The studied palynoflora comprises 21 known acritarch species belonging to 15 genera. One new monospecific genus is described (Calyxia xandaros sp. nov.) as well as one new species of Tanarium (Tanarium anozos sp. nov.). We also propose the genus Knollisphaeridium to replace the preoccupied genus Echinosphaeridium. Three stratigraphically successive assemblages that match previously observed patterns of acritarch replacement are distinguished. The present record is from slightly older strata than in previous records, thus extending the ranges of certain acanthomorphic species. The lower boundaries of three stratigraphically higher assemblage zones among the four formerly established zones, are identified by the occurrence of the index species Tanarium conoideum, Tanarium irregulare and Apodastoides verobturatus, respectively. The substantial morphological disparity of acritarchs in the Giles 1 succession suggests that they may represent a great diversity of microorganisms, not only as biological species but also representing perhaps vegetative and encysted stages in their life cycle. The reconstructed palaeogeographic distribution of several species between Australia, Siberia, Baltica (the East European Platform), and to South China, shows that acritarchs are suitable for both intra- and inter-regional correlation.

    Emneord
    Neoproterozoic, Ediacaran, Acritarchs, Biostratigraphy, Palaeogeography, Officer Basin
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-97148 (URN)10.1016/j.precamres.2007.10.010 (DOI)000255849000009 ()
    Tilgjengelig fra: 2008-04-15 Laget: 2008-04-15 Sist oppdatert: 2022-01-28bibliografisk kontrollert
    3. Acritarchs and their potential in Ediacaran biostratigraphy – Examples from the Officer Basin, Australia
    Åpne denne publikasjonen i ny fane eller vindu >>Acritarchs and their potential in Ediacaran biostratigraphy – Examples from the Officer Basin, Australia
    2007 (engelsk)Inngår i: Comunicações Geológicas, nr 94, s. 81-92Artikkel i tidsskrift (Fagfellevurdert) Published
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-97149 (URN)
    Tilgjengelig fra: 2008-04-15 Laget: 2008-04-15 Sist oppdatert: 2019-04-24bibliografisk kontrollert
    4. Wall ultrastructure of an Ediacaran acritarch from the Officer Basin, Australia
    Åpne denne publikasjonen i ny fane eller vindu >>Wall ultrastructure of an Ediacaran acritarch from the Officer Basin, Australia
    2007 (engelsk)Inngår i: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, Vol. 40, nr 2, s. 111-123Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Well-preserved organic-walled microfossils referred to as acritarchs occur abundantly in Ediacaran deposits in the Officer Basin in Australia. The assemblages are taxonomically diverse, change over short stratigraphical intervals and are largely facies independent across marine basins. Affinities of this informal group of fossils to modern biota are poorly recognized or unknown, with the exception of only a few taxa. Morphological studies by use of transmitted light microscopy, geochemical analyses and other lines of evidence, suggest that some Precambrian acritarchs are related to algae (including prasinophytes, chlorophytes, and perhaps also dinoflagellates). Limitations in magnification and resolution using transmitted light microscopy may be relevant when assessing relationships to modern taxa. Scanning electron microscopy reveals details of morphology, microstructure and wall surface microelements, whereas transmission electron microscopy provides high-resolution images of the cell wall ultrastructure. In the light of previous ultrastructural studies it can be concluded that the division of acritarchs into leiospheres (unornamented) and acanthomorphs (ornamented) is entirely artificial and has no phylogenetic meaning. Examination of Gyalosphaeridium pulchrum using transmission electron microscopy reveals a vesicle wall with four distinct layers. This multilayered wall ultrastructure is broadly shared by a range of morphologically diverse acritarchs as well as some extant microalgae. The chemically resistant biopolymers forming the comparatively thick cell, together with the overall morphology support the interpretation of the microfossil as being in the resting stage in the life cycle. The set of features, morphological and ultrastructural, suggests closer relationship to green algae than dinoflagellates.

    Emneord
    Acritarchs, Australia, Ediacaran, Neoproterozoic, Officer Basin, phytoplankton, protists, TEM, wall ultrastructure
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-97150 (URN)10.1111/j.1502-3931.2007.00023.x (DOI)000246623900002 ()
    Tilgjengelig fra: 2008-04-15 Laget: 2008-04-15 Sist oppdatert: 2019-04-24bibliografisk kontrollert
    5. Morphology and wall ultrastructure of leiosphaeric and acanthomorphic acritarchs from the Ediacaran of Australia
    Åpne denne publikasjonen i ny fane eller vindu >>Morphology and wall ultrastructure of leiosphaeric and acanthomorphic acritarchs from the Ediacaran of Australia
    2009 (engelsk)Inngår i: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 7, nr 1, s. 8-20Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Acritarchs are a group of organic-walled microfossils with unknown biological affinities. The wall ultrastructure of the unornamented, smooth Leiosphaeridia sp. and the acanthomorphic Gyalosphaeridium pulchrum from the Ediacaran Dey Dey Mudstone in the Officer Basin, South Australia, was studied by use of transmission and scanning electron microscopy, and transmitted light microscopy. The study of the ultrastructure reveals a complexity in the cell wall not seen in prokaryotes. Wall ultrastructures range from single-layered to three- or four-layered and from homogeneous to porous. Acritarchs with different wall ultrastructures may be different organisms, but may also reflect different stages in a life cycle. In this paper I review previous ultrastructure studies and discuss possible algal and metazoan affinities for the specimens studied herein.

    HSV kategori
    Forskningsprogram
    Historisk geologi och paleontologi
    Identifikatorer
    urn:nbn:se:uu:diva-88785 (URN)10.1111/j.1472-4669.2008.00178.x (DOI)000263133700002 ()
    Tilgjengelig fra: 2009-03-09 Laget: 2009-02-06 Sist oppdatert: 2019-04-24bibliografisk kontrollert
    6. Taphonomy of Ediacaran acritarchs from Australia: significance for taxonomy and biostratigraphy
    Åpne denne publikasjonen i ny fane eller vindu >>Taphonomy of Ediacaran acritarchs from Australia: significance for taxonomy and biostratigraphy
    2009 (engelsk)Inngår i: Palaios, ISSN 0883-1351, E-ISSN 1938-5323, Vol. 24, nr 3-4, s. 239-256Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A diverse assemblage of Australian Ediacaran (late Neoproterozoic) acritarchs from the Centralian Superbasin and Adelaide Rift Complex demonstrates a range of taphonomic degradation. Recognition of taphonomic variants is critical for taxonomic studies and biostratigraphic interpretation. Taphonomic features observed include compression features, folding and tearing of vesicle walls, pitting, perforation, abrasion, exfoliation, shrinking, twisting, splitting, curling, shredding, pyritization, particle entrapment, and thermal maturation effects. The physical and chemical structure of the vesicle wall is instrumental in determining the degree of taphonomic damage. Consistent associations allow Identification of degradation series that incorporate previously described individual species and provide a framework for taxonomic revision. Taphonomic associations may also characterize taphofacies, providing an additional tool for basin analysis.

    Emneord
    degradation series, correlation, biostratigraphy, late Neoproterozoic, microfossil
    HSV kategori
    Forskningsprogram
    Historisk geologi och paleontologi
    Identifikatorer
    urn:nbn:se:uu:diva-97152 (URN)10.2110/palo.2008.p08-020r (DOI)000264421500010 ()
    Tilgjengelig fra: 2008-04-15 Laget: 2008-04-15 Sist oppdatert: 2019-04-24bibliografisk kontrollert
    7. New records of Ediacaran Acraman ejecta in drillholes from the Stuart Shelf and Officer Basin, South Australia
    Åpne denne publikasjonen i ny fane eller vindu >>New records of Ediacaran Acraman ejecta in drillholes from the Stuart Shelf and Officer Basin, South Australia
    2007 (engelsk)Inngår i: Meteoritics and Planetary Science, ISSN 1086-9379, E-ISSN 1945-5100, Vol. 42, nr 11, s. 1883-1891Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    New occurrences of the Acraman impact ejecta layer were recently discovered in two South Australian drillholes, SCYW-79 1a (Stuart Shelf) and Munta 1 (Officer Basin) using lithostratigraphy, acritarch biostratigraphy, carbon isotope stratigraphy, and biomarker anomalies to predict the stratigraphic position. The ejecta layer is conspicuous because it consists of pink, sand-sized, angular fragments of volcanic rock distributed along the bedding plane surface of green marine siltstone. In SCYW-79 1a it forms a layer 5 mm thick; in Munta 1 the ejecta layer is thin and discontinuous because of its distance (similar to 550 km) from the impact structure. Palynological, biomarker, and carbon isotope anomalies can now be shown to coincide with the ejecta layer in SCYW-79 1a and Munta 1 suggesting the Acraman impact event may have had far reaching influences on the rapidly evolving Ediacaran biological and geochemical cycles.

    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-149876 (URN)000253937700004 ()
    Tilgjengelig fra: 2011-03-24 Laget: 2011-03-24 Sist oppdatert: 2022-01-28bibliografisk kontrollert
    Fulltekst (pdf)
    FULLTEXT01
    Download (pdf)
    COVER01
  • 39.
    Willman, Sebastian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Using TEM to assess the biological affinities of Ediacaran organic-walled microfossils2006Inngår i: Ancient life and modern approaches: Abstracts of the second international palaeontological congress, 2006, s. 553-Konferansepaper (Fagfellevurdert)
  • 40.
    Willman, Sebastian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Bauert, Heikki
    Eliasson, Sara
    Thalheim, Erika
    Generating Geoparks - a Central Baltic initiative2010Inngår i: GEOPARKS: Learning from the Past – Building a Sustainable Future: Celebrating 10 Years of Innovation, 2010Konferansepaper (Annet vitenskapelig)
  • 41.
    Willman, Sebastian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Bauert, Heikki
    Raukas, Anto
    Fostering geotourism on Central Baltic islands2009Konferansepaper (Annet vitenskapelig)
  • 42.
    Willman, Sebastian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Cohen, Phoebe
    Harvard University.
    Ultrastructural Approaches to the Microfossil Record: Assessing Biological Affinities by Use of Transmission Electron Microscopy2011Inngår i: Quantifying the Evolution of Early Life: Numerical Approaches to the Evaluation of Fossils and Ancient Ecosystems / [ed] Marc Laflamme, James D. Schiffbauer and Stephen Q. Dornbos, Dordrecht Heidelberg London New York: Springer , 2011, s. 301-320Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    One of the major technological advances in biological research was the invention and development of the transmission electron microscope, which enables high resolution and high magnification studies of cross-sections of specimens. As such, it has proved to be a useful tool to describe ultrastructural features of taxonomic and phylogenetic importance in modern organisms. Here we discuss how to extend the use of transmission electron microscopy (TEM) to the fossil record, with emphasis on acritarchs (organic-walled microfossils of unknown affinity). Microfossils are traditionally studied by use of transmitted light microscopy, a method that reveals details of external morphology only. TEM however, gives an additional level of detail and reveals structures that can greatly aid in interpretation of taxonomic affinity, and thus can reveal further detail on the origination and diversification of myriad eukaryotic groups in the fossil record. In this chapter we describe the preparation procedure, show advantages and shortcomings of the technique, and discuss how to interpret the results from a geobiological perspective.

  • 43.
    Willman, Sebastian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Grey, Kathleen
    Geological Survey of Western Australia, Perth, Australia.
    Taphonomic analysis of Ediacaran acritarchs and its importance for taxonomy,biostratigraphy and global correlation2008Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this study we analysed the taphonomic degradation history of a diverse assemblage of Ediacaran(late Neoproterozoic) acritarchs from the Centralian Superbasin and Adelaide Rift Complex inAustralia. Taphonomic features observed include compression features, folding and tearing ofvesicle walls, pitting, perforation, abrasion, exfoliation, shrinking, twisting, splitting, curling,shredding, pyritization, particle entrapment, and thermal maturation effects. The physical andchemical structure of the vesicle wall determines the degree of taphonomic damage. Consistentassociations allowed identification of degradation series which incorporate previously describedindividual species and provide a framework for taxonomic revision. Recognition of taphonomicvariants is an important first step in systematic studies, and tracking degradational pathways forparticular species resulted in more precise taxonomic identification. Other biostratigraphicallyuseful fossils are uncommon in the Neoproterozoic which means that considerable reliance willbe placed on acritarch biostratigraphy for future global correlations. It is vital, therefore, that thesignificance of taphonomic degradation, for both taxonomy and palaeoenvironmental analysis, isgiven adequate recognition. Identification of taphonomic variants is critical for taxonomic studiesand must be considered before making biostratigraphic subdivision of the Ediacaran System.

  • 44.
    Willman, Sebastian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Moczydlowska, Malgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Acritarchs in the Ediacaran of Australia — Local or global significance?: Evidence from the Lake Maurice West 1 drillcore2011Inngår i: Review of Palaeobotany and Palynology, ISSN 0034-6667, E-ISSN 1879-0615, Vol. 1-2, nr 166, s. 12-28Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Lake Maurice West 1 drillhole is located in the Officer Basin in South Australia and penetrates a siliciclastic rock succession of Ediacaran age (ca 635–542 Ma). Within this succession well-preserved organic-walled microfossils called acritarchs have been recovered from the Dey Dey Mudstone and Karlaya Limestone, which constitutes a major part of the Ungoolya Group. The assemblage consists of biostratigraphically useful acanthomorphic acritarchs in addition to a diverse assemblage of unornamented leiospheres, filamentous microbiota and some undetermined taxa. Here we describe eight acanthomorphic taxa belonging to three distinctive Ediacaran genera (Cavaspina, Ceratosphaeridium and Tanarium), of which one is described as a new species (Cavaspina amplitudinis sp. nov.). Similar acanthomorphic assemblages are known from Ediacaran strata worldwide and biostratigraphic subdivision of the system based on the occurrence of cosmopolitan taxa is possible in Australia, China, Siberia and Baltica (East European Platform), and perhaps in other areas. The Lake Maurice West 1 microfossil assemblage adds to the growing record of the Ediacaran acritarchs and supports a biostratigraphic scheme for the Ediacaran System at a global scale.

  • 45.
    Willman, Sebastian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Paleobiologi.
    Moczydlowska, Malgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Paleobiologi.
    Grey, Kathleen
    Geological Survey of Western Australia, Perth.
    Acritarchs in the Ediacaran seas2005Inngår i: The Palaeontological Association: 49th Annual Meeting, 18-21 December 2005 University of Oxford, 2005, s. 64-Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The terminal Neoproterozoic radiation of planktonic photosynthetic microbiota (acritarchs) is one of the most significant evolutionary events of the time, including diversification of prokaryotic cyanobacteria and eukaryotic green and brown algae, the appearance of thecoamoebaens and subsequently metazoans (the Ediacara fauna). The Ediacaran radiation of phytoplankton is recognizable by the first appearance of more than fifty new species of large ornamented acritarchs in a short interval of time at ca. 570 Ma. This radiation event occurred after the Snowball Earth conditions returned to a kind of "normal" environmental stasis, and it may be interpreted as a recovery diversification of phytoplankton after a major biotic extinction caused by the global glaciation.

    The appearance of numerous, morphologically innovative and large acritarch taxa may also be connected with the Acraman impact event in South Australia, suggested recently by Grey et al. (2003), as a biotic recovery after the catastrophic environmental disturbance caused by the giant bolide. The latter hypothesis has to be tested, however, because a few individual taxa of ornamented acritarchs may have actually appeared below the ejecta layer, which is difficult to recognize with certainty in some borehole successions.

    The Ediacaran acritarch records are from Australia (the Officer and Amadeus Basins), China and Siberia, showing a worldwide distribution in a relatively short interval of time (ca. 20 Ma; Grey, 2004, in press). The greatest taxonomic diversity is known from Australia (ibidem), and the present study is focused on the investigation of Ediacaran microbiota in greater detail and from different stratigraphic levels, their palaeobiology and affinities, mode of life and reproduction cycle. The new assemblage of organic-walled microfossils from the Murnaroo 1 borehole comprises filamentous cyanobacteria, and ornamented and spheroidal acritarchs.

    The Ediacaran successions in Australia have been well documented in terms of lithostratigraphy, depositional settings and structural geology. The sedimentation proceeded in two different depositional regimes, recognized today in a series of sub-basins. One of them is the Officer Basin, comprised of complex intracratonic, east-west trending troughs and sub-basins extending from Western Australia to South Australia. The studied Murnaroo 1 borehole is also located there. The sediments accumulated in tidal, sub- and intertidal shelf conditions, and the predominantly mudstone lithology from which the samples were collected, is ideal for palynological processing and preservation of microfossils. The lack of macrofossils in the successions rendered efforts and advances in acritarch biostratigraphy since the 1980's, which helped to reveal a complex history of the Officer Basin. The discovery of two distinct palynofloras, an older leiosphere-dominated flora (ELP) and a younger acanthomorph-dominated flora (ECAP), is suggested to be largely environmentally independent (Grey, 2004, in press) in terms of the observed lithology and sedimentological sequences. However, the possible coupling between the Marinoan glaciation, the Acraman impact and the radical change in the palynofloras was inferred (ibidem) and this will be examined with the new data available from the Murnaroo 1 borehole. Previously, the Murnaroo succession was only studied preliminarily.

    In my communication, I will discuss the stratigraphic sequence of appearances of various species and their relationship to the environmental conditions, the Acraman impact event and the changes associated with the global glaciations.

    GREY, K., WALTER, M.R. and CALVER, C.R. (2003) Neoproterozoic biotic diversification: "Snowball Earth" or aftermath of the Acraman impact? Geology 31, p. 459-462.

    GREY, K., (2004, in press) Ediacarian Palynology of Australia. Australasian Association of Palaeontologists, Memoirs.

  • 46.
    Willman, Sebastian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Paleobiologi.
    Moczydlowska, Malgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Grey, Kathleen
    Geological Survey of Western Australia, Perth.
    Neoproterozoic (Ediacaran) diversification of acritarchs - A new record from the Murnaroo 1 drillcore, eastern Officer Basin, Australia2006Inngår i: Review of Paleobotany and Palynology, Vol. 139, s. 17-39Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 47.
    Willman, Sebastian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Moczydłowska, Małgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Wall ultrastructure of an Ediacaran acritarch from the Officer Basin, Australia2007Inngår i: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, Vol. 40, nr 2, s. 111-123Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Well-preserved organic-walled microfossils referred to as acritarchs occur abundantly in Ediacaran deposits in the Officer Basin in Australia. The assemblages are taxonomically diverse, change over short stratigraphical intervals and are largely facies independent across marine basins. Affinities of this informal group of fossils to modern biota are poorly recognized or unknown, with the exception of only a few taxa. Morphological studies by use of transmitted light microscopy, geochemical analyses and other lines of evidence, suggest that some Precambrian acritarchs are related to algae (including prasinophytes, chlorophytes, and perhaps also dinoflagellates). Limitations in magnification and resolution using transmitted light microscopy may be relevant when assessing relationships to modern taxa. Scanning electron microscopy reveals details of morphology, microstructure and wall surface microelements, whereas transmission electron microscopy provides high-resolution images of the cell wall ultrastructure. In the light of previous ultrastructural studies it can be concluded that the division of acritarchs into leiospheres (unornamented) and acanthomorphs (ornamented) is entirely artificial and has no phylogenetic meaning. Examination of Gyalosphaeridium pulchrum using transmission electron microscopy reveals a vesicle wall with four distinct layers. This multilayered wall ultrastructure is broadly shared by a range of morphologically diverse acritarchs as well as some extant microalgae. The chemically resistant biopolymers forming the comparatively thick cell, together with the overall morphology support the interpretation of the microfossil as being in the resting stage in the life cycle. The set of features, morphological and ultrastructural, suggests closer relationship to green algae than dinoflagellates.

  • 48.
    Willman, Sebastian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Peel, John S.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Ineson, Jon R.
    Geological Survey of Denmark and Greenland, Copenhagen, Denmark.
    Schovsbo, Niels H.
    Geological Survey of Denmark and Greenland, Copenhagen, Denmark.
    Rugen, Elias J.
    Department of Geosciences and Natural Resources Management, University of Copenhagen, Copenhagen, Denmark.
    Frei, Robert
    Department of Geosciences and Natural Resources Management, University of Copenhagen, Copenhagen, Denmark.
    Ediacaran Doushantuo-type biota discovered in Laurentia2020Inngår i: Communications Biology, E-ISSN 2399-3642, Vol. 3, nr 1, artikkel-id 647Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Ediacaran period (635-541 Ma) was a time of major environmental change, accompanied by a transition from a microbial world to the animal world we know today. Multicellular, macroscopic organisms preserved as casts and molds in Ediacaran siliciclastic rocks are preserved worldwide and provide snapshots of early organismal, including animal, evolution. Remarkable evolutionary advances are also witnessed by diverse cellular and subcellular phosphatized microfossils described from the Doushantuo Formation in China, the only source showing a diversified assemblage of microfossils. Here, we greatly extend the known distribution of this Doushantuo-type biota in reporting an Ediacaran Lagerstätte from Laurentia (Portfjeld Formation, North Greenland), with phosphatized animal-like eggs, embryos, acritarchs, and cyanobacteria, the age of which is constrained by the Shuram-Wonoka anomaly (c. 570-560 Ma). The discovery of these Ediacaran phosphatized microfossils from outside East Asia extends the distribution of the remarkable biota to a second palaeocontinent in the other hemisphere of the Ediacaran world, considerably expanding our understanding of the temporal and environmental distribution of organisms immediately prior to the Cambrian explosion.

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  • 49.
    Willman, Sebastian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Plado, Jüri
    Raukas, Anto
    Bauert, Heikki
    Meteorite impact structures – geotourism in the central Baltic2010Bok (Annet (populærvitenskap, debatt, mm))
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  • 50.
    Willman, Sebastian
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Slater, Ben
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Late Ediacaran Microfossils from Finland2021Inngår i: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 158, nr 12, s. 2231-2244Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Here we present a detailed accounting of organic microfossils from late Ediacaran sediments of Finland, from the island of Hailuoto (northwest Finnish coast), and the Saarijärvi meteorite impact structure (~170 km northeast of Hailuoto, mainland Finland). Fossils were recovered from fine-grained thermally immature mudstones and siltstones and are preserved in exquisite detail. The majority of recovered forms are sourced from filamentous prokaryotic and protistan-grade organisms forming interwoven microbial mats. Flattened Nostoc-ball-like masses of bundled Siphonophycus filaments are abundant, alongside Rugosoopsis and Palaeolyngbya of probable cyanobacterial origin. Acritarchs include Chuaria, Leiosphaeridia, Symplassosphaeridium and Synsphaeridium. Significantly, rare spine-shaped sclerites of bilaterian origin were recovered, providing new evidence for a nascent bilaterian fauna in the terminal Ediacaran. These findings offer a direct body-fossil insight into Ediacaran mat-forming microbial communities, and demonstrate that alongside trace fossils, detection of a bilaterian fauna prior to the Cambrian might also be sought among the emerging record of small carbonaceous fossils (SCFs).

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