| 1. |
- Agić, Heda, 1989-, et al.
(författare)
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Organically-preserved multicellular eukaryote from the early Ediacaran Nyborg Formation, Arctic Norway
- 2019
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Ingår i: Scientific Reports. - : NATURE PUBLISHING GROUP. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Eukaryotic multicellularity originated in the Mesoproterozoic Era and evolved multiple times since, yet early multicellular fossils are scarce until the terminal Neoproterozoic and often restricted to cases of exceptional preservation. Here we describe unusual organically-preserved fossils from mudrocks, that provide support for the presence of organisms with differentiated cells (potentially an epithelial layer) in the late Neoproterozoic. Cyathinema digermulense gen. et sp. nov. from the Nyborg Formation, Vestertana Group, Digermulen Peninsula in Arctic Norway, is a new carbonaceous organ-taxon which consists of stacked tubes with cup-shaped ends. It represents parts of a larger organism (multicellular eukaryote or a colony), likely with greater preservation potential than its other elements. Arrangement of open-ended tubes invites comparison with cells of an epithelial layer present in a variety of eukaryotic clades. This tissue may have benefitted the organism in: avoiding overgrowth, limiting fouling, reproduction, or water filtration. C. digermulense shares characteristics with extant and fossil groups including red algae and their fossils, demosponge larvae and putative sponge fossils, colonial protists, and nematophytes. Regardless of its precise affinity, C. digermulense was a complex and likely benthic marine eukaryote exhibiting cellular differentiation, and a rare occurrence of early multicellularity outside of Konservat-Lagerstatten.
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| 2. |
- Hoshino, Yosuke, et al.
(författare)
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Cryogenian evolution of stigmasteroid biosynthesis
- 2017
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Ingår i: Science Advances. - : AMER ASSOC ADVANCEMENT SCIENCE. - 2375-2548. ; 3:9
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Tidskriftsartikel (refereegranskat)abstract
- Sedimentary hydrocarbon remnants of eukaryotic C-26-C-30 sterols can be used to reconstruct early algal evolution. Enhanced C-29 sterol abundances provide algal cellmembranes a density advantage in large temperature fluctuations. Here, we combined a literature review with new analyses to generate a comprehensive inventory of unambiguously syngenetic steranes in Neoproterozoic rocks. Our results show that the capacity for C-29 24ethyl- sterol biosynthesis emerged in the Cryogenian, that is, between 720 and 635 million years ago during the Neoproterozoic Snowball Earth glaciations, which were an evolutionary stimulant, not a bottleneck. This biochemical innovation heralded the rise of green algae to global dominance of marine ecosystems and highlights the environmental drivers for the evolution of sterol biosynthesis. The Cryogenian emergence of C-29 sterol biosynthesis places benchmark for verifying older sterane signatures and sets a new framework for our understanding of early algal evolution.
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| 3. |
- Loron, Corentin, et al.
(författare)
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Tonian (Neoproterozoic) eukaryotic and prokaryotic organic-walled microfossils from the upper Visingsö Group, Sweden
- 2018
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Ingår i: Palynology. - : TAYLOR & FRANCIS INC. - 0191-6122 .- 1558-9188. ; 42:2, s. 220-254
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Forskningsöversikt (refereegranskat)abstract
- The diversification of protists and multicellular microorganisms is recorded in numerous worldwide Tonian age successions, including the Visingso Group in Sweden. The Visingso Group contains a taxonomically rich assemblage of cyanobacteria, stromatolites, algal phytoplankton and vase-shaped microfossils. A new record of organic-walled microfossils from the Visingso 1 drillcore reveals the high taxonomic diversity. Several species are reported for the first time from the Visingso Group, and one new species Leiosphaeridia gorda n. sp. is described. They are in gross phycoma-like cysts of the prasinophycean algae Pterospermopsimorpha, Pterospermella, Simia, Macroptycha and Dictyotidium. Morphologically similar to zygotic cysts of chlorophycean algae are Leiosphaeridia gorda n. sp., Cerebrosphaera, Culcitulisphaera and Lanulatisphaera. Schizofusa may represent the earliest yellow-green algae of the Eustigmatiphyte among Stramenopiles. The recorded biodiversity documents the global trend in the evolution of eukaryotic protists during the Tonian Period and the increased radiation of numerous, presumably photoautotrophic biotas, representing various algal lineages.
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| 4. |
- Miao, Lanyun, et al.
(författare)
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A diverse organic-walled microfossil assemblage from the Mesoproterozoic Xiamaling Formation, North China
- 2021
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Ingår i: Precambrian Research. - : Elsevier. - 0301-9268 .- 1872-7433. ; 360
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Tidskriftsartikel (refereegranskat)abstract
- The mid-Proterozoic (ca. 1.85–0.85 Ga) might have been environmentally “boring”, but was a crucial interval of time for the early establishment of eukaryotic life on Earth. The Mesoproterozoic shale-dominated Xiamaling Formation (ca. 1.4–1.35 Ga) in North China preserved abundant organic-walled microfossils, some of which were of eukaryotic affinity but their taxonomic diversity and evolutionary implications remain unclear. In this paper, we present a palynological study of the lower Xiamaling Formation in the northern Tianjin Municipality. Similar to other Mesoproterozoic microbiotas, this assemblage consists of well-preserved and diverse spheroidal to ellipsoidal vesicles, filamentous microfossils and cellular aggregates. In total, 36 species belonging to 28 genera are identified, including 1 new species Quadrimurus clavatus gen. et sp. nov., and 5 unnamed forms. Majority of these taxa are recognised for the first time from this formation, indicating a richer assemblage than previously known. Although most taxa are of unknown biological affinities, this microbiota is thought to be composed of prokaryotic and eukaryotic microorganisms, in which 12 taxa are inferred to be eukaryotic. These microfossils indicate a moderate diversity of eukaryotic life documented in the Xiamaling Formation, which is consistent with other microbiotas in the mid-Proterozoic. The presence of Jixiania lineata Yan, 1986 (=Lineaforma elongata Vorob’eva and Sergeev, 2015) in North China extends its geographic distribution and further enhances its potential as index fossil for the early Mesoproterozoic strata. The Xiamaling assemblage provides one of the broader pictures of the Mesoproterozoic biosphere, in which eukaryotes were predominantly protistan-grade microorganisms.
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| 5. |
- Miao, Lanyun, et al.
(författare)
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New record of organic-walled, morphologically distinct microfossils from the late Paleoproterozoic Changcheng Group in the Yanshan Range, North China
- 2019
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Ingår i: Precambrian Research. - : ELSEVIER SCIENCE BV. - 0301-9268 .- 1872-7433. ; 321, s. 172-198
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Tidskriftsartikel (refereegranskat)abstract
- Eukaryotic life has likely existed since the late Paleoproterozoic, yet little is known about its early diversity and phylogenetic relationships. Organic-walled microfossils (OWMs) with conspicuous morphology provide a unique material to investigate the deep evolution of eukaryotic and prokaryotic microbial clades. Here we report a diverse assemblage of OWMs from the lower Changcheng Group (c. 1673-1638 Ma, Changzhougou and Chuanlinggou formations) in the Yanshan Range, North China, which consists of 15 species, including 2 that are newly described. The fossil assemblage is dominated by spheromorphs with less numerous process-bearing vesicles, as are colonial and filamentous forms. Among these, 6 morphologically complex taxa (Dictyosphaera, 2 species of Germinosphaera, Pterospermopsimorpha, Simia, and Valeria) are identified as unambiguous unicellular eukaryotes. Four species (Cucumiforma, Navifusa, Schizofusa and large Leiosphaeridia) with relatively simple morphology but having large size, thick wall, and some showing median-split excystment structures, are of probable eukaryotic affinity. However, various colonial microfossils could be either eukaryotes or prokaryotes. The new record of morphologically disparate OWMs represents one of the earliest occurrences of eukaryotes in both China and the world, and indicates that the eukaryotic life was already well established in the late Paleoproterozoic and was of moderate diversity, similar to that of the Mesoproterozoic.
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| 6. |
- Moczydlowska, Malgorzata, 1951-, et al.
(författare)
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A Tonian age for the Visingsö Group in Sweden constrained by detrital zircon dating and biochronology : implications for evolutionary events
- 2018
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Ingår i: Geological Magazine. - 0016-7568 .- 1469-5081. ; 155:5, s. 1175-1189
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Tidskriftsartikel (refereegranskat)abstract
- Detrital zircon U–Pb ages from samples of the Neoproterozoic Visingsö Group, Sweden, yield a maximum depositional age of ≤ 886±9 Ma (2σ). A minimum depositional age is established biochronologically using organic-walled and vase-shaped microfossils present in the upper formation of the Visingsö Group; the upper formation correlates with the Kwagunt Formation of the 780–740 Ma Chuar Group in Arizona, USA, and the lower Mount Harper Group, Yukon, Canada, that is older than 740 Ma. Mineralized scale microfossils of the type recorded from the upper Fifteenmile Group, Yukon, Canada, where they occur in a narrow stratigraphic range and are younger than 788 Ma, are recognized for the first time outside Laurentia. The mineralized scale microfossils in the upper formation of the Visingsö Group seem to have a wider stratigraphic range, and are older than c. 740 Ma. The inferred age range of mineralized scale microfossils is 788–740 Ma. This time interval coincides with the vase-shaped microfossil range because both microfossil groups co-occur. The combined isotopic and biochronologic ages constrain the Visingsö Group to between ≤ 886 and 740 Ma, thus Tonian in age. This is the first robust age determination for the Visingsö Group, which preserves a rich microfossil assemblage of worldwide distribution. The organic and mineralized microorganisms preserved in the Visingsö Group and coeval successions elsewhere document global evolutionary events of auto- and heterotrophic protist radiations that are crucial to the reconstruction of eukaryotic phylogeny based on the fossil record and are useful for the Neoproterozoic chronostratigraphic subdivision.
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| 7. |
- Moczydlowska, Malgorzata, 1951-
(författare)
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New records of late Ediacaran microbiota from Poland
- 2008
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Ingår i: Precambrian Research. - Amsterdam : Elsevier. - 0301-9268 .- 1872-7433. ; 167:1-2, s. 71-92
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Forskningsöversikt (refereegranskat)abstract
- New records of organic-walled microfossils, including cyanobacteria, phytoplankton (certain acritarchs) and some microbiota of unknown biological affinities, are reported from the late Ediacaran Włodawa Formation in the Łopiennik IG-1 borehole, Poland. The microfossil association consists mostly of known species, which originated prior to the Cryogenian Period, evidence that these microorganisms survived the Neoproterozoic glacial epochs. The longevity of most of the species is extended herein to ca. 545 Ma. One species is new but described as gen. et sp. indet., because only a single specimen is available. Although the microfossils represent both prokaryotic and eukaryotic groups of organisms, and benthic and planktic modes of life, all, with the exception of Valkyria, are photoautotrophic aerobes. Metabolic processes of nutrition, respiration and reproductive cycles, and ecologic habitats of these biota and the evolutionary lineages to which they belong are analyzed with respect to the basic requirements needed to survive prolonged periods of environmental perturbation.All recorded here cyanobacteria are benthic microbial mat-dwellers, requiring ample water and regular oxygen supply and sun light for their metabolism. Planktic species of Leiosphaeridia studied here are considered to be green algae (chlorophyceans), forming resting cysts and alternating sexual/vegetative generations in their life cycle. They also required habitats of well-oxygenated open water in the photic zone and periodic access to bottom sediment (to rest the cyst) in order to survive the glacial epochs, as they evidently did. It is argued that the natural habitats of all these biota must have been preserved and ecologically functional throughout the Cryogenian Period, and have been robust enough to sustain viable populations and genetic stocks of at least some evolutionary lineages known at the time. This is a primary constraint imposed by contemporaneous marine biosphere on the Earth System model, which can be accepted among hypothetical versions of the Snowball Earth hypotheses based on sedimentological, geochemical, physical and other geological records. The Slushball Earth model, or comparable, is thus favoured over strict Snowball Earth model because it reconciles the habitable conditions with other envisaged geo- and physical conditions during the period.
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| 8. |
- Moczydlowska, Malgorzata, 1951-
(författare)
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The Ediacaran microbiota and the survival of Snowball Earth conditions
- 2008
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Ingår i: Precambrian Research. - Amsterdam : Elsevier. - 0301-9268 .- 1872-7433. ; 167:1-2, s. 1-15
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Forskningsöversikt (refereegranskat)abstract
- Recently recovered assemblage of late Ediacaran cyanobacteria, phytoplankton and some microfossils of uncertain origin from the subsurface Włodawa Formation on the Lublin Slope in Poland, allowed to extend their stratigraphic ranges and provided a new evidence that more species survived the Cryogenian Period. Numerous other species of unicellular eukaryotes (informally called acritarchs) and prokaryotes (also coenobial and colonial) have been documented in recent years to lived-over to the Ediacaran, enlarging the global list of biota surviving the Neoproterozoic icehouse intervals. This compelling record revives the issue how marine biota could coup with the catastrophic consequences imposed by the global glaciations and/or to what extent the environmental and climatic change reduced the life habitats. For this purpose, the metabolic processes, modes of life and ecologic habitats of the biota are inferred and analyzed. The reviewed biota are autotrophic and aerobic: benthic cyanobacteria, which were solitary and largely colonial, living in functionally complex communities of mat-builders, and planktic and/or facultative benthic eukaryotes, which reproduced also sexually and some had advanced life cycle with alternating vegetative and reproductive generations. The environmental requirements of these microorganisms are well-oxygenated open marine waters in the photic zone, and permanent seafloor substrate for benthic and periodic access to bottom sediment for some planktic species with sexual reproduction to rest the cyst. Such natural habitats must have been preserved throughout the Cryogenian Period, and in a substantial extent (environmental “critical mass”) to sustain viable populations in the lineages that are represented by surviving species. Modern analogues of extraordinary adaptations of diverse biota to extreme conditions have their limitations when applied to the Cryogenian Period. Modern extreme environments (like those in Antarctica) with highly specialized organisms are maintained over relatively short time intervals (thousands of years) and may occasionally/periodically be in contact with the outside world to replenish their genetic stock. This is in a sharp contrast to the millions of years of environmental and genetic isolation invoked for the Cryogenian. The global fossil record, enlarged by recent new findings, is briefly reviewed to understand the impact of the Cryogenian glaciations on biodiversity and the rate of survival of microbiota. The Snowball Earth Hypothesis and its modified versions are discussed in pursuit of an environmentally plausible Earth System model consistent with the survival of biota. The radical version of the Snowball Earth Hypothesis is ruled out. An Earth System model with open marine water, ice-free shelf (at least seasonally) and access to the sea floor is obligatory for the Cryogenian in order to satisfy the living requirements of the biota that survived the period. The palaeobiological findings are entirely consistent with sedimentaological findings that require open marine water and well-functioning hydrologic cycle. The Slushball Earth model accommodates more adequately these requirements.
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| 9. |
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| 10. |
- Moczydlowska-Vidal, Malgorzata, 1951-, et al.
(författare)
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Ediacaran algal cysts from the Doushantuo Formation, South China
- 2022
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Ingår i: Geological Magazine. - : Cambridge University Press. - 0016-7568 .- 1469-5081. ; 159:7, s. 1050-1070
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Tidskriftsartikel (refereegranskat)abstract
- Early-middle Ediacaran organic-walled microfossils from the Doushantuo Formation studied in several sections in the Yangtze Gorges area, South China, show ornamented cyst-like vesicles of very high diversity. These microfossils are diagenetically permineralized and observed in petrographic thin-sections of chert nodules. Exquisitely preserved specimens belonging to seven species of Appendisphaera, Mengeosphaera, Tanarium, Urasphaera and Tianzhushania contain either single or multiple spheroidal internal bodies inside the vesicles. These structures indicate reproductive stages, endocyst and dividing cells, respectively, and are preserved at early to late ontogenetic stages in the same taxa. This new evidence supports the algal affiliations for the studied taxa and refutes previous suggestions of Tianzhushania being animal embryo or holozoan. The first record of a late developmental stage of a completely preserved specimen of T. spinosa observed in thin-section demonstrates the interior of vesicles with clusters of identical cells but without any cavity that is diagnostic for recognizing algal cysts vs animal diapause cysts. Various lines of evidence to infer biological affinities of these microfossils - morphology, reproductive characters, spatial arrangement of cells, and biochemical properties of the vesicle wall - are collectively characteristic of algal clades. Recognizing the biological affinities of these microfossils is key to understanding whether animals capable of producing such morphologically complex diapause cysts had an early Ediacaran fossil record (633-610 Ma), or the microfossils were non-animal holozoans or algae as argued herein for Tianzhushania spinosa and other studied microfossils.
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