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  • 951.
    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 correlation2008Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 952.
    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 drillcore2011Ingår i: Review of Palaeobotany and Palynology, ISSN 0034-6667, E-ISSN 1879-0615, Vol. 1-2, nr 166, s. 12-28Artikel i tidskrift (Refereegranskat)
    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.

  • 953.
    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 seas2005Ingår i: The Palaeontological Association: 49th Annual Meeting, 18-21 December 2005 University of Oxford, 2005, s. 64-Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 954.
    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, Australia2006Ingår i: Review of Paleobotany and Palynology, Vol. 139, s. 17-39Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 955.
    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.
    Ediacaran acritarch biota from the Giles 1 drillhole, Officer Basin, Australia, and its potential for biostratigraphic correlation2008Ingår i: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 162, nr 3-4, s. 498-530Artikel, forskningsöversikt (Refereegranskat)
    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.

  • 956.
    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, Australia2007Ingår i: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, Vol. 40, nr 2, s. 111-123Artikel i tidskrift (Refereegranskat)
    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.

  • 957.
    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 (Övrig (populärvetenskap, debatt, mm))
  • 958. Wilson, George D. F.
    et al.
    Paterson, John R.
    Kear, Benjamin P.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Fossil isopods associated with a fish skeleton from the lower cretaceous of Queensland, Australia: Direct evidence of a scavenging lifestyle in mesozoic cymothoida2011Ingår i: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 54, nr 5, s. 1053-1068Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A dense assemblage of fossil isopod crustaceans (Brunnaega tomhurleyi Wilson, sp. nov.) from the Lower Cretaceous (Albian) Toolebuc Formation of Queensland, Australia, has been found within the carcass of a large actinopterygian fish, Pachyrhizodus marathonensis (Etheridge). Preservation of fine anatomical details supports referral to the genus Brunnaega Polz, which is herein reassigned to the family Cirolanidae. Furthermore, placement of this taxon within the cirolanid subfamily Conilerinae Kensley and Schotte is significant because the group includes modern species that are well known as voracious scavengers. This isopod-fish association represents the oldest unequivocal evidence of scavenging by Mesozoic cymothoidean isopods on a large vertebrate carcass.

  • 959. Winter, Amos
    et al.
    Henderiks, Jorijntje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Beaufort, Luc
    Rickaby, Rosalind E. M.
    Brown, Christopher W.
    Poleward expansion of the coccolithophore Emiliania huxleyi2014Ingår i: Journal of Plankton Research, ISSN 0142-7873, E-ISSN 1464-3774, Vol. 36, nr 2, s. 316-325Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coccolithophores are one of the most abundant eukaryotic phytoplankton in the oceans and are distinguished by their ability to build calcitic platelets (coccoliths). Of the numerous species, Emiliania huxleyi is considered one of the major calcifiers in the pelagic ocean. There is growing concern that increasing levels of CO2 in the atmosphere and the subsequent acidification of the ocean may disrupt the production of coccoliths. Furthermore, any change in the global distribution and abundance of E. huxleyi relative to non-calcifying groups of phytoplankton (e.g. diatoms) will have important effects on the biogeochemical cycling of carbon and climatic feedbacks. We review different lines of evidence that suggest E. huxleyi is increasingly expanding its range into the polar oceans. These observations contribute to the debate on the climatic effects on natural coccolithophore populations. We postulate that E. huxleyi may be more sensitive to recent environmental changes such as increasing sea surface temperature and salinity than to changing ocean carbonate chemistry, partly because increased availability of CO2(aq) likely alleviates a carbon limitation for the inefficient Rubisco enzyme in these algae. Any potentially important climatic feedbacks of coccolithophores need a better knowledge of the mechanisms and rates of adaptation by natural populations. As more data and modelling work become available, the real significance of this poleward expansion will become clear.

  • 960. Wohlfarth, B
    et al.
    Blaauw, M
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Davies, SM
    Andersson, M
    Wastegård, S
    Hormes, A
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Jonfysik. Jonfysik.
    Possnert, G
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Jonfysik. Jonfysik.
    Constraining the age of Lateglacial and early Holocene pollen zones and tephra horizons in southern Sweden with Bayesian probability methods2006Ingår i: Journal of Quaternary Science, Vol. 21, s. 321-334Artikel i tidskrift (Refereegranskat)
  • 961.
    Wretman, Lovisa
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för organismbiologi, Evolution och utvecklingsbiologi.
    Kear, Benjamin P.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Bite marks on an ichthyodectiform fish from Australia: possible evidence of trophic interaction in an Early Cretaceous marine ecosystem2014Ingår i: Alcheringa, ISSN 0311-5518, E-ISSN 1752-0754, Vol. 38, nr 2, s. 170-176Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A well-preserved fish skull from late Albian deposits of the Allaru Mudstone near Richmond in Queensland displays a conspicuous V-shaped pattern of indentations, punctures and depression fractures consistent with a vertebrate bite trace. This is the first direct evidence of trophic interaction between vertebrates within an Early Cretaceous marine ecosystem from Australia. The specimen is taxonomically referable to the largebodied (ca 1m snouttail length) ichthyodectiform Cooyoo australis, but the size and spacing of the tooth marks is incompatible with attack by a conspecific individual. The lack of osseous growths concordant with healing also suggests that the bite occurred shortly before or after the animals death. Comparison with the dentitions of other coeval vertebrates indicates compatible tooth arrangements in longirostrine amniote predators such as polycotylid plesiosaurians, ornithocheiroid pterosaurs and especially the ichthyosaurian Platypterygius. The implications of this as a potential predatorprey association are that Early Cretaceous actinopterygians occupied middle-level trophic niches and were in turn consumed by higher-level amniote carnivores, similar to many extant marine vertebrate communities of today.

  • 962.
    Xiao, Shuhai
    et al.
    Virginia Tech, Dept Geosci, Blacksburg, VA 24061 USA..
    Narbonne, Guy M.
    Queens Univ, Dept Geol Sci & Geol Engn, Kingston, ON K7L 3N6, Canada..
    Zhou, Chuanming
    Chinese Acad Sci, Nanjing Inst Geol & Palaeontol, Key Lab Econ Stratig & Palaeogeog, Nanjing 210008, Jiangsu, Peoples R China..
    Laflamme, Marc
    Univ Toronto, 3359 Mississauga Rd, Mississauga, ON L5L 1C6, Canada..
    Grazhdankin, Dmitriy V.
    Russian Acad Sci, Siberian Branch, Trofimuk Inst Petr Geol & Geophys, Prospekt Akad Koptyuga 3, Novosibirsk 630090, Russia..
    Moczydlowska-Vidal, Malgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Cui, Huan
    Univ Wisconsin, Dept Geosci, Madison, WI 53706 USA.;Univ Wisconsin, NASA Astrobiol Inst, Madison, WI 53706 USA..
    Towards an Ediacaran Time Scale: Problems, Protocols, and Prospects2016Ingår i: Episodes, ISSN 0705-3797, Vol. 39, nr 4, s. 540-555Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Ediacaran Period follows the Cryogenian Period in the wake of a snowball Earth glaciation and precedes the Cambrian Period with its rising tide of animal radiation. It is also the longest among all stratigraphically defined geological periods, lasting 94 million years (635-541 Ma). Hence, a good Ediacaran time scale is essential, not only to elucidate geological time, but also to provide a temporal context for extreme climatic events and transformative evolutionary transitions. Ediacaran fossils are known from many sections and boreholes around the world, permitting ready age recognition and stratigraphic correlation of Ediacaran strata. However, the Ediacaran fossil record is colored by taphonomic biases that variously affect the preservation of the soft-bodied organisms that dominated Ediacaran marine ecosystems, and the Phanerozoic approach of defining stratigraphic boundaries using the first appearance datum (FAD) of widely distributed, rapidly evolving, easily recognizable, and readily preservable species would have limited success in the Ediacaran System. The subdivision of the Ediacaran System must therefore be founded on a holistic approach integrating biostratigraphic, chemostratigraphic, and geochronometric data for correlation. Series-level subdivision of the Ediacaran System is a challenging task, and alternative models subdividing the Ediacaran System into two or three series can be recognized. Resolving these alternatives critically depends on obtaining further data to constrain the age, duration, and global extent of the Shuram negative delta C-13 excursion, to calibrate and correlate Ediacaran acanthomorph biozones, and to determine the temporal relationship among the Shuram excursion, the Gaskiers glaciation, and Ediacaran acanthomorph biozones. Stage-level subdivisions at the bottom and top of the Ediacaran System, however, are realistic goals in the near future, and we propose that the subdivision of the Ediacaran System should initially aim at the second Ediacaran stage (SES) and the terminal Ediacaran stage (TES) where stratigraphic information is relatively rich and consensus for stratigraphic correlation is emerging. Potential stratigraphic markers for the definition of the SES include the post-glacial radiation of eukaryotes as represented by the first appearance of acanthomorph acritarchs, the termination of the cap carbonate series, or the end of the negative delta C-13 excursion (EN1 = Ediacaran negative excursion 1) associated with the cap carbonate. Terminal Ediacaran strata are well dated and host several taxa of skeletal and tubular fossils that postdate the Shuram negative delta C-13 excursion (or its probable equivalent, EN3 = Ediacaran negative excursion 3) where their stratigraphic relationship can be determined; these biostratigraphic markers may be used to define the TES in a Phanerozoic fashion. Additional Ediacaran stages between the SES and TES can be envisioned. Through collaborative efforts in the Ediacaran community, we hope that the first Precambrian stage will be established in the near future to facilitate a better understanding of the geological aftermath of snowball Earth, the redox history of global oceans, the early evolution of multicellular life, and the evolutionary fuse of the Cambrian explosion.

  • 963. Yeloff, D
    et al.
    Bennett, Keith D.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Blaauw, Maarten
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Mauquoy, D
    Silassoo, Ü
    van der Plicht, J
    van Geel, B
    High precision C-14 dating of Holocene peat deposits: a comparison of Bayesian calibration and wiggle-matching approaches2006Ingår i: Quaternary Geochronology, ISSN 1871-1014, Vol. 1, nr 3, s. 222-235Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The chronologies of five northern European ombrotrophic peat bogs subjected to a large ANIS C-14 dating effort (32-44 dates/site) are presented here. The results of Bayesian calibration (BCal) of dates with a prior assumption of chronological ordering were compared with a Bayesian wiggle-match approach (Bpeat) which assumes constant linear accumulation over sections of the peat profile. Interpolation of BCal age estimates of dense sequences of C-14 dates showed variable patterns of peat accumulation with time, with changes in accumulation occurring at intervals ranging from 20 to 50 cm. Within these intervals, peat accumulation appeared to be relatively linear. Close analysis suggests that some of the inferred variations in accumulation rate were related to the plant macrofossil composition of the peat. The wiggle-matched age-depth models had relatively high chronological uncertainty within intervals of closely spaced 14 C dates, suggesting that the premise of constant linear accumulation over large sections of the peat profile is unrealistic. Age models based on the assumption of linear accumulation over large parts of a peat core (and therefore only effective over millennial timescales), are not compatible with studies examining environmental change during the Holocene, where variability often occurs at decadal to centennial time-scales. Ideally, future wiggle-match age models should be constrained, with boundaries between sections based on the plant macrofossil composition of the peat and physical-chemical parameters such as the degree of decomposition. Strategies for the selection of material for dating should be designed so that there should be enough C-14 dates to accurately reconstruct the peat accumulation rate of each homogeneous stratigraphic unit.

  • 964.
    Yu, Shi-Yong
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. PALAEOBIOLOGY.
    Andrén, Elinor
    Barnekow, Lena
    Berglund, Björn, E.
    Sandgren, Per
    Holocene palaeoecology and shoreline displacement on the Biskopsmåla Peninsula, southeastern Sweden2003Ingår i: BOREAS, ISSN 0300-9483, Vol. 32, s. 578-589Artikel i tidskrift (Refereegranskat)
  • 965.
    Zammit, Maria
    et al.
    University of Adelaide.
    Kear, Benjamin P.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Healed bite marks on a Cretaceous ichthyosaur2011Ingår i: Acta Palaeontologica Polonica, ISSN 0567-7920, E-ISSN 1732-2421, Vol. 56, nr 4, s. 859-863Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reports of pathological ichthyosaur fossils are very rare. The identification of a series of healed cuts and an associated gouge on the lower jaw of an adult (ca 5 metres body length) Platypterygius specimen from the Lower Cretaceous of Australia is therefore significant, because it constitutes direct evidence of bite force trauma sustained during the life of the animal. Based on the close spacing and non-lethal facial positioning of the wounds, they were probably not inflicted by a predator. Alternative explanations might include an accidental aggressive encounter with another large vertebrate, or perhaps an intraspecific interaction such as during courtship or combat over food, mates or territory.

  • 966.
    Zammit, Maria
    et al.
    University of Adelaide.
    Kear, Benjamin P.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Norris, Rachel
    University of Adelaide.
    Platypterygius australis − Mesozoic dolphin?2011Ingår i: 2011 CAVEPS Proceedings. Geological Survey of Western Australia 2011/9, 2011, s. 92-Konferensbidrag (Övrigt vetenskapligt)
  • 967. Zammit, Maria
    et al.
    Kear, Benjamin P.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Norris, Rachel M.
    Locomotory capabilities in the Early Cretaceous ichthyosaur Platypterygius australis based on osteological comparisons with extant marine mammals2014Ingår i: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 151, nr 1, s. 87-99Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Reconstructing the swimming capabilities of extinct marine tetrapods is critical for unravelling broader questions about their palaeobiology, palaeoecology and palaeobiogeography. Ichthyosaurs have long been the subject of such investigations because, alongside cetaceans, they are one of the few tetrapod lineages to achieve a highly specialized fish-like body plan. The dominant locomotory mode for the majority of derived, post-Triassic ichthyosaurs is hypothesized to have been caudal fin-driven propulsion. Limb-based swimming has however been suggested for some highly autapomorphic forms, such as the Cretaceous genus Platypterygius, which has a remarkably robust humeral morphology and exceptionally broad paddle-like limbs. To evaluate this atypical lifestyle model, we conducted a comprehensive comparative osteological assessment of Platypterygius in relation to extant marine mammals, whose analogous skeletal frameworks provide a structurally compatible selection of alternate propulsive strategies. Based on a proxy exemplar of the most completely known species, P.australis from the Early Cretaceous of Australia, the propodial shape, absence of functional elbow/knee joints, tightly interlocking carpals, hyperphalangy and extreme reduction of the pelvic girdle are most similar to cetaceans as opposed to pinnipeds or dugongs. There is no obvious structural consistency with aquatic mammals that use sustained forelimb-driven swimming. The exceptionally broad fore-paddle (a product of hyperdactyly) and extensive humeral muscle insertions might therefore have had a cetacean-like role in enhancing manoeuvrability and acceleration performance. We conclude that, despite its atypical features, P. australis was most likely similar to other ichthyosaurs in using lateral sweeps of the tailfin to generate primary propulsive thrust.

  • 968.
    Zammit, Maria
    et al.
    School of Earth and Environmental Sciences, North Terrace Campus, University of Adelaide, Adelaide, South Australia, Australia.
    Norris, Rachel M.
    School of Animal and Veterinary Sciences, Roseworthy Campus, University of Adelaide, Adelaide, South Australia, Australia.
    Kear, Benjamin P.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    The Australian Cretaceous ichthyosaur Platypterygius australis: a description and review of postcranial remains2010Ingår i: Journal of Vertebrate Paleontology, ISSN 0272-4634, E-ISSN 1937-2809, Vol. 30, nr 6, s. 1726-1735Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Australian Cretaceous ichthyosaur material is amongst the most complete in the world. This study describes postcranial remains referred to the upper Albian species Platypterygius australis, including the first record of pelvic and hindlimb elements for this taxon. A combination of phylogenetically significant traits such as lack of fusion between the atlas-axis complex and third cervical centrum, the presence of three distal facets on both the humerus/femur for accommodation of the anterior zeugopodial elements plus the radius/tibia and ulna/fibula, concave preaxial accessory facet surfaces on both the humerus and the femur, and complete fusion of the ischiopubis with closure of the obturator foramen, are considered diagnostic for the species and (in conjunction with other previously identified cranial/postcranial features) may serve to distinguish P. australis from the other paleogeographically disparate Platypterygius spp.

  • 969. Zang, Wen-long
    et al.
    Moczydlowska, Malgorzata
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Jago, James
    Early Cambrian acritarch assemblage zones in South Australia and global correlation2007Ingår i: Memoirs of the Association of Australasian Palaeontologists, ISSN 0810-8889, Vol. 33, s. 141-177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lower Cambrian sediments in the Arrowie and Stansbury Basins were deposited on a rifting continental platform and contain abundant acritarchs, trace fossils, small shelly fossils, archaeocyaths, trilobites and brachiopods. Generally, faunas and acritarchs are abundant in transgressive and highstand deposits, but less common in lowstand fluvial deposits, responding both to sedimentary environments and preservational conditions. Seven acritarch Assemblage Zones are recognised in the lowest Cambrian to Toyonian sediments of South Australia. Assemblage Zone 1 embraces the Precambrian-Cambrian boundary, but a dramatic increase of spinose acritarchs (Assemblage Zone 2) is observed around 1 m above the first appearance of the trace fossil Rusophycus. Assemblage Zone 3 occurs in transgressive siltstones during deposition of the uppermost Parachilna Formation and is marked by the first appearance of several taxa, which are widespread and well correlated in South Australia. Assemblage Zones 4, 5 and 6 are dominated by Skiagia; the appearance of S. ornata followed by S. ciliosa in Zones 4 and 5, respectively, indicates correlation with the nominal acritarch zones on the East European Platform and concurrent Schmidtiellus mickwitzi and Holmia kjerulfi trilobite zones, and the Qiongzhusi Formation in southern China. Assemblage Zone 7 encompasses a major acritarch decrease in South Australia during the late early Cambrian regression and 'red-beds' deposition. Continuous occurrences of acritarch genera Skiagia, Ceratophyton and Corollasphaeridium during the early Cambrian provide valuable evidence of evolutionary development, and therefore are reliable for biostratigraphic zonation. The integration of biostratigraphy and unconformity-bounded sequence stratigraphy provides more precise intercontinental correlation.

  • 970. Zhang, Yi Ge
    et al.
    Pagani, Mark
    Henderiks, Jorijntje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Ren, Haojia
    A long history of equatorial deep-water upwelling in the Pacific Ocean2017Ingår i: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 467, s. 1-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cold, nutrient-and CO2-rich waters upwelling in the eastern equatorial Pacific (EEP) give rise to the Pacific cold tongue. Quasi-periodic subsidence of the thermocline and attenuation in wind strength expressed by El Niño conditions decrease upwelling rates, increase surface-water temperatures in the EEP, and lead to changes in regional climates both near and far from the equatorial Pacific. EEP surface waters have elevated CO2concentrations during neutral (upwelling) or La Niña (strong upwelling) conditions. In contrast, approximate air–sea CO2equilibrium characterizes El Niño events. One hypothesis proposes that changes in physical oceanography led to the establishment of a deep tropical thermocline and expanded mixed-layer prior to 3 million years ago. These effects are argued to have substantially reduced deep-water upwelling rates in the EEP and promoted a “permanent El Niño-like” climate state. For this study, we test this supposition by reconstructing EEP “excess CO2” and upwelling history for the past 6.5million years using the alkenone-pCO2methodology. Contrary to previous assertions, our results indicate that average temporal conditions in the EEP over the past ∼6.5 million years were characterized by substantial CO2disequilibrium and high nutrient delivery to surface waters — characteristics that imply strong upwelling of deep waters. Upwelling appears most vigorous between ∼6.5 to 4.5 million years ago coinciding with high accumulation rates of biogenic material during the late Miocene – early Pliocene “biogenic bloom”.

  • 971. Zhang, Yige
    et al.
    Pagani, Mark
    Henderiks, Jorijntje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Ren, Haojia
    A long history of equatorial upwelling in the Pacific Ocean2014Konferensbidrag (Övrigt vetenskapligt)
  • 972. Zhang, Yige
    et al.
    Pagani, Mark
    Henderiks, Jorijntje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Ren, Haojia
    The late Miocene “paradox” of CO2 climate sensitivity2013Konferensbidrag (Övrigt vetenskapligt)
  • 973.
    Zhang, Zhifei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Han, J.
    Wang, Y.
    Emig, Christian C.
    Shu, D.-G.
    Epibionts on the lingulate brachiopod Diandongia from the Early Cambrian Chengjiang Lagerstatte, South China2010Ingår i: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 277, s. 175-181Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The classic Chengjiang Lagerstatte (Lower Cambrian, Atdabanian stage: Yu'anshan Formation) Yunnan, southwestern China, has yielded, besides the exceptional and often controversial soft-bodied fossils, a fauna of primitive/early lingulid brachiopods. Diandongia pista (Rong 1974) is one of the commonest and most strongly mineralized of the phosphatic brachiopods from the Lagerstatte. The shells of this species have been found to commonly serve as a basibiont host. Epibionts comprise the coeval brachiopod Longtancunella chengjiangensis and the cone-shaped cnidarian-related Archotuba conoidalis, as well as rounded smaller-sized epizoans (lesser than 2 mm). A principle morphological analysis demonstrates that the ovoid and rounded organisms that often occur along the commissure of D. pista resemble small juvenile or immature brachiopods. Epibiont-bearing shells of D. pista with soft-tissue preservation demonstrate that the host brachiopods were overgrown while alive, and provide an argument for D. pista having a semiinfaunal life style with only the slim pedicle embedded in sediment. The epibiotic association sheds direct light on the ecology of Cambrian brachiopods in soft-substrate marine environments. The Chengjiang fossils demonstrate that the Early Cambrian brachiopods, as compared with recent lingulids, occupied different and a wider spectrum of ecological niches and tiers of space.

  • 974. Zhang, Zhifei
    et al.
    Holmer, L. E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Exceptionally preserved brachiopods from the Chengjiang Lagerstatte (Yunnan, China): Perspectives on the Cambriane explosion of metazoans2013Ingår i: Science Foundation in China, ISSN 1005-0841, Vol. 21, nr 2, s. 66-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Cambrian explosion was coined to describe the geologically sudden appearance of numerous bilaterian body plans (Phyla) around the Ediacaran-Cambrian transition, around 565-520 million years ago. Many explanations and conjectures have been postulated in order to explain the pattern and duration of this explosive radiation of many different phyla of early metazoans. Here, we focus on the evolution of a phylum of marine suspension-feeding animals – the brachiopods, as exemplified by the exceptionally preserved taxa from the celebrated Chengjiang Konservat Lagerstätte (Yunnan, China). The abundant soft-bodied preservation at these fossil quarries gives us the only firm insights into what brachiopods looked like and how they functioned and lived when they first appeared on the Earth. Studies of Chengjiang brachiopods demonstrate that the early animals developed a remarkable varied organization of tissues and organs shortly after the onset of Cambrian explosion. In the marine suspension-feeding brachiopods, most importantly the tentaculate feeding structure of early brachiopods is already differentiated into two shapes of lophophore, anteriorly coiled (spiralled) and posteriorly arching tentacle crowns and the unique latter type was previously not documented from fossil and living brachiopods. Also unlike any known Recent brachiopod, all the known Cambrian brachiopods from Chengjiang have an open digestive tract that was disposed either as a U-shaped gut in linguliform and stem group brachiopods, or straight gut with a posterior anus in some calcareous-shelled stocks. Moreover, in contrast to living lingulids, all the Cambrian brachiopods have an epibenthic lifestyle either cemented by a ventral valve or attached by variable pedicles to establish complex ecological community encompassing primary tierers and variable secondary tierers. It is therefore assumed that brachiopods were the first benthic metazoan that achieved their success in ecological stratification and tiering complexity by late Atdabanian. The setae are also important for the brachiopod suspension-feeding life style, and in the Chengjiang brachiopods they include two types - cilia-like and spine-like setae. The mantle canals of different brachiopod species are also distinctly variable in arrangement, mainly disposed in pinnate, baculate and peripheral conditions. Of these, the peripheral disposition of mantle canals is for the first time proposed here so as to differentiate from the bifurcate condition in recent lingulids in that the former is devoid of posteriorly extending main trunks of sinus, but possesses a diverging dorsal vascular media in dichotomy.

  • 975. Zhang, Zhifei
    et al.
    Holmer, Lars E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Ou, Qiang
    Han, Jian
    Shu, Degan
    The exceptionally preserved Early Cambrian stem rhynchonelliform brachiopod Longtancunella and its implications2011Ingår i: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, Vol. 44, nr 4, s. 490-495Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The extraordinary Longtancunella chengjiangensis is one of the rarest and most problematic brachiopods from the Early Cambrian Chengjiang Lagerstatte, where it occurs in unique gregarious clusters with up to ten individuals attached by their stout pedicles to a single hard exoskeleton. Although the general morphology and soft anatomy of Longtancunella is available, its taxonomy and systematic placement within the Brachiopoda remains problematic. New exceptionally preserved specimens show that the pedicle of Longtancunella cannot be considered homologous with the pedicles in crown Rhynchonelliformea or Linguliformea. The pedicle of Longtancunella emerges from a ventral umbonal foramen with a rounded plate that must have been secreted by specialized ventral mantle epithelium. The rounded plate is proposed to be a homologue to the colleplax - a plate covering the umbonal foramen, which is otherwise known from the extinct rhynchonelliform chileates. Longtancunella is proposed to represent a soft-shelled stem rhynchonelliform brachiopod with chileate features, thus demonstrating for the first time that the chileate-like umbonal perforation functions as a pedicle opening. The unusual preservation of the annulated chileate-like holdfast supports the view that it may have been secreted as stacks of chitinous or even mineralized 'attachment pads'. Together with having a spirolophous lophophore and U-shaped gut, Longtancunella displays a unique mixture of linguliform and rhynchonelliform characters that throw new light on an early stage of rhynchonelliform diversification.

  • 976. Zhang, Zhifei
    et al.
    Holmer, Lars E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Popov, Leonid
    Shu, Degan
    An obolellate brachiopod with soft-part preservation from the early cambrian chengjiang fauna of China2011Ingår i: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 85, nr 3, s. 460-463Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The obolellates represent a poorly understood group of the oldest known cosmopolitan calcareous rhynchonelliform brachiopods. They made their first appearance in the early Atdabanian and became extinct at the end of the Middle Cambrian. Consequently, any information concerning the soft anatomy of this ephemeral lineage of brachiopods has great phylogenetic significance. This is the first report on two specimens of an obolellate with fine preservation of soft parts including the pedicle, marginal setae and possible imprints of a spiral lophophore, recovered from the early Cambrian Chengjiang Konservat Lagerstatte of Kunming, southern China. The setae are thin and densely fringed along the shell margin. The stout pedicle is distinctly composed of densely stacked tabular bodies, lacking a central coelomic lumen; it emerges through a possible foramen, and slightly tapers posteriorly with the distal end attached to exoskeletons of other organisms.

  • 977.
    Zhang, Zhifei
    et al.
    Early Life Institute, State Key Laboratory of Continental Dynamics, Northwest University, Xi'an, 710069, China.
    Holmer, Lars E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Robson, Sean P.
    The Manitoba Museum, 190 Rupert Avenue, Winnipeg, Manitoba, Canada.
    Hu, Shixue
    Yunnan Geological Survey &Yunnan Institute of Geological Science, No. 87, Dongfeng Lane, East Dongfeng Road, Kunming, 650051, Yunnan Province, China.
    Wang, Xiangren
    Early Life Institute, State Key Laboratory of Continental Dynamics, Northwest University, Xi'an, 710069, China.
    Wang, Haizhou
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    First record of repaired durophagous shell damages in Early Cambrian lingulate brachiopods with preserved pedicles2011Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 302, nr 3-4, s. 206-212Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Durophagy, the macro-predatory consumption of hard-shelled organisms, has been proposed as an important driving and selective force ("arms race") responsible for the explosive advent of Cambrian skeleton-bearing animals. Nevertheless, the direct evidence of durophagous predation is mostly restricted to borings or drillholes in skeletons at around the Ediacaran-Cambrian transition. In contrast, pre-ingestive breakage or crushing of shell, another important type of durophagous predation evidence, is very rarely fossilized. Here we present the first evidence of durophagous shell-breaking in an exceptionally preserved pedunculate lingulate brachiopod from the Lower Cambrian Wulongqing Formation (Series 2, early Stage 4), Yunnan, southern China. The repaired shells of Diandongia pista all have elongate (up to 36 mm) pedicles that demonstrate that they survived the failed predation and remained in situ. The bite embayment shows three sets of distinctive drape-like convex arcs of shell repairs, suggesting that the specific drape-like ornamentation usually seen in lingulate shells could be taken as reparative responses to shell damage and malformation. Discovery of sublethal shell damage demonstrates that durophagous predators may have caused an increasing predation pressure on brachiopods since the Canglangpuian Stage (Series 2, Stage 4). In contrast there are no records of durophagous shell-breaking recognized from thousands of Chengjiang (Series 2, Stage 3) specimens of D. pista with fully developed organization of tissues and organ system. It is therefore assumed that that predation was of little importance to the earliest evolution of Cambrian lingulates.

  • 978. Zhang, Zhifei
    et al.
    Holmer, Lars E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Skovsted, Christian B.
    Brock, Glenn A.
    Budd, Graham E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Fu, Dongjing
    Zhang, Xingliang
    Shu, Degan
    Han, Jian
    Liu, Jianni
    Wang, Haizhou
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Butler, Aodhan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Li, Guoxiang
    A sclerite-bearing stem group entoproct from the early Cambrian and its implications2013Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, s. 1066-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Lophotrochozoa includes disparate tentacle-bearing sessile protostome animals, which apparently appeared in the Cambrian explosion, but lack an uncontested fossil record. Here we describe abundant well preserved material of Cotyledion tylodes Luo et Hu, 1999, from the Cambrian (Series 2) Chengjiang deposits, reinterpreted here as a stem-group entoproct. The entoproct affinity is supported by the sessile body plan and interior soft anatomy. The body consists of an upper calyx and a lower elongate stalk with a distal holdfast. The soft anatomy includes a U-shaped gut with a mouth and aboral anus ringed by retractable marginal tentacles. Cotyledion differs from extant entoprocts in being larger, and having the calyx and the stalk covered by numerous loosely-spaced external sclerites. The description of entoprocts from the Chengjiang biota traces the ancestry of yet another lophotrochozoan phylum back to the Cambrian radiation, and has important implications for the earliest evolution of lophotrochozoans.

  • 979.
    Zhang, Zhifei
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Holmer, Lars
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Wang, Haizhou
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Butler, Aodhán D.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    An early Cambrian agglutinated tubular lophophorate with brachiopod characters2014Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, s. 4682-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The morphological disparity of lophotrochozoan phyla makes it difficult to predict the morphology of the last common ancestor. Only fossils of stem groups can help discover the morphological transitions that occurred along the roots of these phyla. Here, we describe a tubular fossil Yuganotheca elegans gen.et sp. nov. from the Cambrian (Stage 3) Chengjiang Lagerstätte (Yunnan, China) that exhibits an unusual combination of phoronid, brachiopod and tommotiid (Cambrian problematica) characters, notably a pair of agglutinated valves, enclosing a horseshoe-shaped lophophore, supported by a lower bipartite tubular attachment structure with a long coelomic pedicle providing anchorage. The discovery has important implications for the early evolution of lophotrochozoans, suggesting rooting of brachiopods into the sessile lophotrochozoans and the origination of their bivalved bauplan preceding the biomineralization of shell valves in crown brachiopods.

  • 980. Zhang, Zhifei
    et al.
    Zhang, Zhiliang
    Holmer, Lars Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Li, Guoxiang
    First report of linguloid brachiopods with soft parts from the lower Cambrian (Series 2, Stage 4) of the Three Gorges area, South China2015Ingår i: Annales de Paléontologie, ISSN 0753-3969, E-ISSN 1778-3666, Vol. 101, nr 3, s. 167-177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract Chengjiang-type fossil brachiopods with preservation of non-mineralized tissues are reported for the first time from the Lower Cambrian Shipai Formation of the Three Gorges area, western Hubei Province, China. Recent excavation in the Wangjiaping and Aijiahe sections resulted in the new discovery of some linguloid brachiopods, showing strong similarity in preservation with those occurring in the well-known Chengjiang fauna (Yu’anshan Formation of eastern Yunnan, China). The brachiopods can be referred to Palaeobolus liantuoensis, Lingulellotreta malongensis and Eoobolus. sp. The new material of Palaeobolus exhibits a flattened impression of proximal pedicle, which also represents the first report of pedicle known from this cosmopolitan linguloid taxon. The occurrence of Lingulellotreta in the Shipai Formation (Redlichia meitanensis and Palaeolenus lantenoisi zones) represents an important geological extension of this genus to upper Tsanglangpuan Stage (Series 2, Stage 4) in the Yangtze Platform, and signifying that the FAD of Lingulellotreta in the regional Lower Cambrian of the Yangtze Platform seems not synchronous.

  • 981.
    Zhang, Zhi-Fei
    et al.
    Northwest Univ, State Key Lab Continental Dynam, Early Life Inst, Xian 710069, Peoples R China.
    Zhang, Zhi-Liang
    Northwest Univ, State Key Lab Continental Dynam, Early Life Inst, Xian 710069, Peoples R China.
    Li, Guo-Xiang
    Chinese Acad Sci, Nanjing Inst Geol & Palaeontol, LPS, Nanjing 210008, Jiangsu, Peoples R China.
    Holmer, Lars E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    The Cambrian brachiopod fauna from the first-trilobite age Shuijingtuo Formation in the Three Gorges area of China2016Ingår i: Palaeoworld, ISSN 1871-174X, Vol. 25, nr 3, s. 333-355Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Yangtze platform of South China offers evidence within its Ediacaran–Cambrian geological record of the Cambrian explosion and diversificationevents in metazoan history. To understand the explosive radiation of animals and the environments in which it took place, the basalCambrian fauna succession of the Aijiahe section in the Three Gorges area, western Hubei Province, has been studied, revealing the earliestbrachiopod fauna (Tsunyidiscus trilobite Zone) in this region, which was dominated numerically by acrotretoids. This is accompanied by abundantskeletal fossils including minute well-preserved phosphatized archaeocyath cups and an assortment of abundant sponge spicules, chancelloriids,mollusks, hyoliths, and bradoriids, retrieved by acid-etching limestone interbeds in the black shale-dominated Shuijingtuo Formation (Series 2).The brachiopods comprise two species of acrotretoids, two types of botsfordiids (Botsfordiidae gen. et sp. indet. A and B), and four species oflinguloids. Of the latter, Spinobolus popovi n. gen. n. sp. is strikingly distinctive and typified by spine-like ornamentation seen for the first time in thelower Cambrian; the remaining three linguloid genera, Palaeobolus, Eoobolus, and Lingulellotreta, have a trans-paleocontinental distribution. TheThree Gorges Shuijingtuo brachiopod assemblage differs from that of the upper Atdabanian Stage (Cambrian Stage 3) in Siberia and South China,but shows great similarities with those discovered in the Tsanglangpuan (equivalent to Botoman or Stage 4) Stage of eastern Yunnan Province,Siberia, and South Australia, suggesting a much more prolonged sedimentary hiatus in basalmost Shuijingtuo Formation of the Three Gorges areathan previously expected. The presence of such unconformities provides a caveat to stable isotope-based correlations that involve a number ofdiscussions of global ocean geochemical changes across the time interval that witnessed Cambrian explosion of metazoans.

  • 982.
    Zhang, Zhiliang
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Shaanxi Key laboratory of Early Life and Environments and Department of Geology, State Key Laboratory of Continental Dynamics, Northwest University, Xi’an, China.
    Popov, Leonid E.
    Department of Geology, National Museum of Wales, Cardiff, UK.
    Holmer, Lars E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Shaanxi Key laboratory of Early Life and Environments and Department of Geology, State Key Laboratory of Continental Dynamics, Northwest University, Xi’an, China.
    Zhang, Zhifei
    Shaanxi Key laboratory of Early Life and Environments and Department of Geology, State Key Laboratory of Continental Dynamics, Northwest University, Xi’an, China.
    Earliest ontogeny of early Cambrian acrotretoid brachiopods: first evidence for metamorphosis and its implications2018Ingår i: BMC Evolutionary Biology, ISSN 1471-2148, E-ISSN 1471-2148, Vol. 18, artikel-id 42Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Our understanding of the ontogeny of Palaeozoic brachiopods has changed significantly during the last two decades. However, the micromorphic acrotretoids have received relatively little attention, resulting in a poor knowledge of their ontogeny, origin and earliest evolution. The uniquely well preserved early Cambrian fossil records in South China provide a great new opportunity to investigate the phylogenetically important ontogeny of the earliest acrotretoid brachiopods, and give new details of the dramatic changes in anatomy of acrotretoid brachiopods during the transition from planktotrophic larvae to filter feeding sedentary juveniles.

  • 983.
    Zhang, Zhi-liang
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Northwest Univ, Shaanxi Key Lab Early Life & Environm, State Key Lab Continental Dynam, Xian 710069, Shaanxi, Peoples R China.;Northwest Univ, Dept Geol, Xian 710069, Shaanxi, Peoples R China..
    Skovsted, Christian B.
    Northwest Univ, Shaanxi Key Lab Early Life & Environm, State Key Lab Continental Dynam, Xian 710069, Shaanxi, Peoples R China.;Northwest Univ, Dept Geol, Xian 710069, Shaanxi, Peoples R China.;Swedish Museum Nat Hist, Dept Palaeobiol, Box 50007, SE-10405 Stockholm, Sweden..
    Zhang, Zhi-fei
    Northwest Univ, Shaanxi Key Lab Early Life & Environm, State Key Lab Continental Dynam, Xian 710069, Shaanxi, Peoples R China.;Northwest Univ, Dept Geol, Xian 710069, Shaanxi, Peoples R China..
    A hyolithid without helens preserving the oldest hyolith muscle scars; palaeobiology of Paramicrocornus from the Shujingtuo Formation (Cambrian Series 2) of South China2018Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 489, s. 1-14Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hyolithid Paramicrocornus zhenbaensis from the lower Cambrian (Cambrian Series 2) Shuijingtuo Formation of southern Shaanxi and western Hubei provinces of the Yangtze Platform is well-preserved in three dimensions. The morphology of the conch and operculum of P.zhenbaensis shows that this species lacked helens, which are considered to be characteristic of hyolithids and hence Paramicrocornus may belong to a sister group of other hyolithids. The shell structure of P.zhenbaensis reveals close similarities to the shell structure of other hyolithids. Furthermore, the smaller size and non-radial orientation of tubules in the shell structure of the operculum also differ from that in orthothecid hyoliths, suggesting that this characteristic may be used to differentiate hyolithids and orthothecids. The phosphatized opercula of P. zhenbaensis exhibit a pair of muscle scars located close to the apex of the internal surface. These muscle scars, as well as similar structures in other hyolithids, probably served as attachment sites of muscles controlling the retraction of the tentaculate feeding organ recently discovered in hyolithids. Without helens, P. zhenbaensis may have been sessile with the conch partly buried in the sea floor. (C) 2017 Published by Elsevier B.V.

  • 984.
    Zhang, Zhi-liang
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Shaanxi Key Laboratory of Early Life and Environment, Department of Geology and State Key Laboratory of Continental Dynamics, Northwest University, China.
    Zhang, Zhi-fei
    Shaanxi Key Laboratory of Early Life and Environment, Department of Geology and State Key Laboratory of Continental Dynamics, Northwest University, China.
    Holmer, Lars E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Shaanxi Key Laboratory of Early Life and Environment, Department of Geology and State Key Laboratory of Continental Dynamics, Northwest University, China.
    Studies on the shell ultrastructure and ontogeny of the oldest acrotretid brachiopods from South China2017Ingår i: Acta Palaeontologica Sinica, Vol. 54, nr 4, s. 483-503Artikel i tidskrift (Refereegranskat)
  • 985.
    Zhang, Zhiliang
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Northwest University, Xi’an.
    Zhang, Zhifei
    Northwest University, Xi’an.
    Holmer, Lars E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Northwest University, Xi’an.
    Chen, Feiyang
    Northwest University, Xi’an.
    Post-metamorphic allometry in the earliest acrotretoid brachiopods from the lower Cambrian (Series 2) of South China, and its implications2018Ingår i: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 61, nr 2, s. 183-207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The earliest growth of post-metamorphic (post-larval) shells in two species of Eohadrotreta is described from the Cambrian Shuijingtuo Formation of South China. Two different growth patterns can be observed by quantifying developmental variations in size and shape of successive stages of post-metamorphic shell growth (including the pedicle foramen forming stage, pedicle foramen enclosing stage and intertrough increasing stage) of Eohadrotreta zhenbaensis and Eohadrotreta? zhujiahensis. The pedicle foramen is never enclosed within the metamorphic shell of E. zhenbaensis, while the enclosed pedicle foramen of E.? zhujiahensis is located directly outside the metamorphic shell after the pedicle foramen enclosing stage. A strongly allometric growth pattern of E. zhenbaensis is demonstrated by the early enclosure of the pedicle foramen; an accelerated lengthening of the ventral intertrough is associated with the development of a more complex dorsal median septum during the intertrough increasing stage. By contrast, E.? zhujiahensis demonstrates possible paedomorphic development by delayed enclosure of pedicle foramen and an associated decreased lengthening of ventral intertrough during the intertrough increasing stage. This ontogenetic developmental sequence represents the marginal accretionary formation and growth of the pedicle foramen, which resembles that of linguloid brachiopods. Furthermore, the developmental process of the pedicle foramen of Eohadrotreta seems to recapitulate the likely evolutionary transition from the Botsfordiidae, with open delthyrium, to the Acrotheloidea, with an enclosed foramen. This study provides a unique opportunity to obtain a complete understanding of the ontogenetic development of the earliest acrotretoids, and casts new light on the phylogeny of lingulate brachiopods.

  • 986.
    Zhang, Zhiliang
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Northwest Univ, Early Life Inst, State Key Lab Continental Dynam, Xian 710069, Peoples R China.
    Zhang, Zhifei
    Northwest Univ, Early Life Inst, State Key Lab Continental Dynam, Xian 710069, Peoples R China..
    Wang, Haizhou
    China Univ Petr, Dept Geol, Beijing 102249, Peoples R China..
    Epithelial cell moulds preserved in the earliest acrotretid brachiopods from the Cambrian (Series 2) of the Three Gorges area, China2016Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 138, nr 4, s. 455-466Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Distinctive moulds of epithelial cells are known to occur on valve interiors in early Palaeozoic acrotretid brachiopods but morphological variation and distributional patterns of the epithelial cells imprints remains poorly known. Herein, we present for the first time a detailed study of exquisitely preserved epithelial cell moulds and shell micro-structures in acid-etched material of the earliest acrotretid brachiopod Eohadrotreta zhenbaensis from the Shuijingtuo Formation (Cambrian Series 2) of Aijiahe section, approximately 25km north-west of Yichang City, western Hubei Province. The ventral and dorsal epithelial cell moulds (on average 18m across) are usually isometrically convex or concave polygonal with a variable outline (tetragon, pentagon and hexagon). Investigation of the new material demonstrates that the disposition of pronounced epithelial cell pustules or depressions in shell interiors most likely is associated with regions of thickened muscle attachments in ventral and dorsal valves - a character that potentially could be of use in taxonomy, though detailed comparative studies of such epithelial microstructures of acrotretids and other brachiopod taxa remain to be done.

  • 987.
    Zigaite, Zivile
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för organismbiologi, Evolution och utvecklingsbiologi.
    Kear, Benjamin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Joachimski, Michael M.
    University of Erlangen-Nuremberg.
    Tutken, Thomas
    University of Bonn.
    Whitehouse, Martin
    Naturhistoriska Riksmuseet.
    Blom, Henning
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för organismbiologi, Evolution och utvecklingsbiologi.
    Geochemistry of dental bioapatite, the key to palaeoclimate2013Ingår i: Proceedings of the 3rd IGCP 591 Annual Meeting, Lund, Sweden, 9-19 June 2013 / [ed] Anders Lindskog and Kristina Mehlqvist, Lund: Department of Geology, Lund University , 2013, s. 361-362Konferensbidrag (Refereegranskat)
  • 988.
    Zigaite, Zivile
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för organismbiologi, Evolution och utvecklingsbiologi.
    Kear, Benjamin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Perez-Huerta, Alberto
    University of Alabama.
    Jeffries, Teresa
    Natural History Museum.
    Do fossil vertebrate biominerals hold the key to Palaeozoic climate?2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fossil vertebrate hard tissues - teeth and dermoskeleton - are considered among the most geochemically stable biominerals, and therefore are widely used for palaeoenvironmental and palaeoclimatic reconstructions. Elemental and isotopic compositions of fossil dental tissues may provide unique palaeoenvironmental information, ranging from the diet and trophic positions on a food chain, to the palaeosalinity and water temperatures of ancient seas. However, before starting any geochemical interpretations, the preservation potential of fossil tissues must be studied carefully, considering possible alteration of the primary geochemical composition. Evaluation of fossil hard tissue preservation can be made by semiquantitative spot geochemistry analyses on fine polished teeth and scale thin sections using Energy Dispersive X-ray Spectroscopy (EDS), and help to roughly preview the chemical composition. The Electron Backscatter Diffractometry (EBSD) is useful to examine the cristallinity and possible structural alterations. In addition, rare earth element (REE) abundances can be measured in situ within the fine fossil tissues (such as enamel vs. dentine) using Laser Ablation Inductively Coupled Plasma Mass-spectrometry (LA-ICP-MS), and give us information about the selective geochemical resilience between separate vertebrate hard tissues. To conclude, in order to decipher the geochemical signal of fossil biominerals correctly, the evaluation of preservation should be the starting point to any further geochemical studies.

  • 989.
    Zigaite, Zivile
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för organismbiologi, Evolution och utvecklingsbiologi.
    Perez-Huerta, Alberto
    University of Alabama.
    Jeffries, Teresa
    Natural History Museum.
    Kear, Benjamin P
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Blom, Henning
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Biologiska sektionen, Institutionen för organismbiologi, Evolution och utvecklingsbiologi.
    Geochemistry of fossilised dental remains - key to palaeobiology and palaeoenvironment.2013Ingår i: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 135, nr 1, s. 25-Artikel i tidskrift (Refereegranskat)
  • 990. Zuykov, M. A.
    et al.
    Egerquist, Eva
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. Palaeobiology.
    The Upper Ordovician and lower Silurian Platystrophia-like brachiopods from Sweden2004Konferensbidrag (Övrigt vetenskapligt)
  • 991. Zykov, Michael A.
    et al.
    Egerquist, Eva
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    A new Platystrophia-like brachiopod genus from the Ordovician Boda Limestone of Dalarna, Sweden2005Ingår i: GFF, Vol. 127, nr 1, s. 1-5Artikel i tidskrift (Refereegranskat)
  • 992.
    Šupraha, Luka
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi.
    Phenotypic evolution and adaptive strategies in marine phytoplankton (Coccolithophores)2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Coccolithophores are biogeochemically important marine algae that interact with the carbon cycle through photosynthesis (CO2 sink), calcification (CO2 source) and burial of carbon into oceanic sediments. The group is considered susceptible to the ongoing climate perturbations, in particular to ocean acidification, temperature increase and nutrient limitation. The aim of this thesis was to investigate the adaptation of coccolithophores to environmental change, with the focus on temperature stress and nutrient limitation. The research was conducted in frame of three approaches: experiments testing the physiological response of coccolithophore species Helicosphaera carteri and Coccolithus pelagicus to phosphorus limitation, field studies on coccolithophore life-cycles with a method comparison and an investigation of the phenotypic evolution of the coccolithophore genus Helicosphaera over the past 15 Ma. Experimental results show that the physiology and morphology of large coccolithophores are sensitive to phosphorus limitation, and that the adaptation to low-nutrient conditions can lead to a decrease in calcification rates. Field studies have contributed to our understanding of coccolithophore life cycles, revealing complex ecological patterns within the Mediterranean community which are seemingly regulated by seasonal, temperature-driven environment changes. In addition, the high-throughput sequencing (HTS) molecular method was shown to provide overall good representation of coccolithophore community composition. Finally, the study on Helicosphaera evolution showed that adaptation to decreasing CO2 in higher latitudes involved cell and coccolith size decrease, whereas the adaptation in tropical ecosystems also included a physiological decrease in calcification rates in response to nutrient limitation. This thesis advanced our understanding of coccolithophore adaptive strategies and will improve our predictions on the fate of the group under ongoing climate change.

    Delarbeten
    1. Eco-physiological adaptation shapes the response of calcifying algae to nutrient limitation
    Öppna denna publikation i ny flik eller fönster >>Eco-physiological adaptation shapes the response of calcifying algae to nutrient limitation
    2015 (Engelska)Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, artikel-id 16499Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The steady increase in global ocean temperature will most likely lead to nutrient limitation in the photic zone. This will impact the physiology of marine algae, including the globally important calcifying coccolithophores. Understanding their adaptive patterns is essential for modelling carbon production in a low-nutrient ocean. We investigated the physiology of Helicosphaera carteri, a representative of the abundant but under-investigated flagellated functional group of coccolithophores. Two strains isolated from contrasting nutrient regimes (South Atlantic and Mediterranean Sea) were grown in phosphorus-replete and phosphorus-limited batch cultures. While growing exponentially in a phosphorus-replete medium, the Mediterranean strain exhibited on average 24% lower growth rate, 36% larger coccosphere volume and 21% lower particulate inorganic carbon (PIC) production than the Atlantic strain. Under phosphorus limitation, the same strain was capable of reaching a 2.6 times higher cell density than the Atlantic strain due to lower phosphorus requirements. These results suggest that local physiological adaptation can define the performance of this species under nutrient limitation.

    Nationell ämneskategori
    Ekologi Cellbiologi Evolutionsbiologi Geovetenskap och miljövetenskap
    Identifikatorer
    urn:nbn:se:uu:diva-253354 (URN)10.1038/srep16499 (DOI)000364487200001 ()26560531 (PubMedID)
    Forskningsfinansiär
    Knut och Alice Wallenbergs StiftelseKungliga Vetenskapsakademien
    Tillgänglig från: 2015-05-26 Skapad: 2015-05-26 Senast uppdaterad: 2017-12-04Bibliografiskt granskad
    2. High temperature decreases the PIC/POC ratio and increases phosphorus requirements in Coccolithus pelagicus (Haptophyta)
    Öppna denna publikation i ny flik eller fönster >>High temperature decreases the PIC/POC ratio and increases phosphorus requirements in Coccolithus pelagicus (Haptophyta)
    Visa övriga...
    2014 (Engelska)Ingår i: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, s. 3531-3545Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Rising ocean temperatures will likely increase stratification of the water column and reduce nutrient input into the photic zone. This will increase the likelihood of nutrient limitation in marine microalgae, leading to changes in the abundance and composition of phytoplankton communities, which in turn will affect global biogeochemical cycles. Calcifying algae, such as coccolithophores, influence the carbon cycle by fixing CO2 into particulate organic carbon through photosynthesis (POC production) and into particulate inorganic carbon through calcification (PIC production). As calcification produces a net release of CO2, the ratio of PIC to POC production determines whether coccolithophores act as a source (high PIC / POC) or a sink (low PIC / POC) of atmospheric CO2. We studied the effect of phosphorus (P-) limitation and high temperature on the physiology and the PIC / POC ratio of two subspecies of Coccolithus pelagicus. This large and heavily calcified species is a major contributor to calcite export from the photic zone into deep-sea reservoirs. Phosphorus limitation did not influence exponential growth rates in either subspecies, but P-limited cells had significantly lower cellular P-content. One of the subspecies was subjected to a 5 °C temperature increase from 10 °C to 15 °C, which did not affect exponential growth rates either, but nearly doubled cellular P-content under both high and low phosphate availability. This temperature increase reduced the PIC / POC ratio by 40–60%, whereas the PIC / POC ratio did not differ between P-limited and nutrient-replete cultures when the subspecies were grown near their respective isolation temperature. Both P-limitation and elevated temperature significantly increased coccolith malformations. Our results suggest that a temperature increase may intensify P-limitation due to a higher P-requirement to maintain growth and POC production rates, possibly reducing abundances in a warmer ocean. Under such a scenario C. pelagicus may decrease its calcification rate relative to photosynthesis, thus favouring CO2 sequestration over release. It seems unlikely that P-limitation by itself causes changes in the PIC / POC ratio in this species.

    Nyckelord
    coccolithophores, culture experiments, phosphate limitation, calcification
    Nationell ämneskategori
    Naturvetenskap
    Forskningsämne
    Biologi; Geovetenskap med inriktning mot miljöanalys
    Identifikatorer
    urn:nbn:se:uu:diva-220830 (URN)10.5194/bg-11-3531-2014 (DOI)000339265800008 ()
    Tillgänglig från: 2014-03-20 Skapad: 2014-03-20 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
    3. Phosphorus availability modifies carbon production in Coccolithus pelagicus (Haptophyta)
    Öppna denna publikation i ny flik eller fönster >>Phosphorus availability modifies carbon production in Coccolithus pelagicus (Haptophyta)
    Visa övriga...
    2015 (Engelska)Ingår i: Journal of Experimental Marine Biology and Ecology, ISSN 0022-0981, E-ISSN 1879-1697, Vol. 472, s. 24-31Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Abstract The coccolithophore Coccolithus pelagicus (Wallich) Schiller fixes CO2 into particulate organic carbon (POC) through photosynthesis and into particulate inorganic carbon (PIC) in the form of calcite. To examine the role of phosphorus (P) availability in the production of POC and PIC, C. pelagicus subsp. braarudii (Gaarder) Geisen et al. was grown in semi-continuous cultures at three initial phosphate concentrations (P-replete, 1, and 0.5 μM [P]). Reduced P-availability (1 and 0.5 μM [P]) decreased POC production, while PIC production only decreased when phosphate concentrations became growth limiting (0.5 μM [P]). This decrease has not been observed previously in batch cultures, highlighting the inadequacy of the batch culture approach with regard to determining carbon production. The reduction in growth rate by 50% at 0.5 μM [P] was accompanied by a doubling in cell volume (and POC). PIC production was halved, resulting in a lowered PIC to POC ratio. The average number of coccoliths per cell (and PIC content) remained the same among treatments, despite the significant change in cell size. Our data suggest that POC production in C. pelagicus is more sensitive towards a moderate reduction in phosphorus availability than PIC production. Once phosphorus availability limits cell division, however, phosphorus resources are invested into POC rather than PIC production. This reduces cell density and sinking rates, indicating that coccoliths do not act as ballast for reaching deeper nutrient-rich layers under nutrient limitation.

    Nyckelord
    Calcification, Carbon production, Coccolithus pelagicus, Phosphorus limitation, Semi-continuous culture
    Nationell ämneskategori
    Mikrobiologi Cellbiologi
    Identifikatorer
    urn:nbn:se:uu:diva-301334 (URN)
    Tillgänglig från: 2016-08-19 Skapad: 2016-08-19 Senast uppdaterad: 2017-11-28
    4. Observations on the life cycle and ecology of Acanthoica quattrospina Lohmann from a Mediterranean estuary
    Öppna denna publikation i ny flik eller fönster >>Observations on the life cycle and ecology of Acanthoica quattrospina Lohmann from a Mediterranean estuary
    2014 (Engelska)Ingår i: Journal of Nannoplankton Research, ISSN 1210-8049, Vol. 34, nr SI, s. 49-56Artikel i tidskrift (Refereegranskat) Published
    Nationell ämneskategori
    Ekologi Biologisk systematik
    Identifikatorer
    urn:nbn:se:uu:diva-253353 (URN)
    Konferens
    INA Workshop on Extant Coccolithophores research
    Tillgänglig från: 2015-05-26 Skapad: 2015-05-26 Senast uppdaterad: 2016-09-13Bibliografiskt granskad
    5. Coccolithophore life-cycle dynamics in a coastal Mediterranean ecosystem: seasonality and species-specific patterns
    Öppna denna publikation i ny flik eller fönster >>Coccolithophore life-cycle dynamics in a coastal Mediterranean ecosystem: seasonality and species-specific patterns