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A new species of small acritarch with porous wall structure from the early Cambrian of Estonia, and implications for the fossil record of eukaryotic picoplankton
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. (ORIGINS AND EARLY DIVERSIFICATION OF PHOTOSYNTHETIC MICROBIOTA)ORCID iD: 0000-0002-4002-4141
2015 (English)In: Palynology, ISSN 0191-6122, E-ISSN 1558-9188, Vol. 40, no 3, 343-356 p.Article in journal (Refereed) Published
Abstract [en]

The Proterozoic-Phanerozoic transition records a general trend of decrease in phytoplankton cell size, in contrast tothe earlier and much larger Ediacaran acritarchs. Particularly minute, unornamented but sculptured organic-walledmicrofossils have been recovered from the lower Cambrian Lükati Formation in northern Estonia. The lack of anysignificant thermal alteration in the formation allowed for excellent preservation of fine microstructures on thesemicrofossils. Among the rich palynomorph assemblage in Lükati, a new species of tiny, spheroidal eukaryoticmicrofossil is recorded: Reticella corrugata gen. et sp. nov. It is characterised by a corrugated and flexible vesicle wallthat is densely perforated by nano-scale pores. Despite its unique morphology, the new species shares diagnosticcharacters with fossil and extant prasinophyte algae. R. corrugata is among the smallest microfossils with typicaleukaryotic morphology (conspicuous wall sculpture) and contributes to the diversity of the size class of smallacritarchs. Size, abundance, inferred prasinophyte affinity and eukaryotic wall sculpture make this new taxon alikely member of the early eukaryotic picoplankton.

Place, publisher, year, edition, pages
2015. Vol. 40, no 3, 343-356 p.
Keyword [en]
Cambrian, Estonia, organic-walled microfossils, picoplankton, prasinophytes, small acritarchs
National Category
Geology Ecology
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
Identifiers
URN: urn:nbn:se:uu:diva-265208DOI: 10.1080/01916122.2015.1068879ISI: 000386047200007OAI: oai:DiVA.org:uu-265208DiVA: diva2:864106
Projects
Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
Funder
Swedish Research Council, 621-2012-1669
Available from: 2015-10-25 Created: 2015-10-25 Last updated: 2017-11-10Bibliographically approved
In thesis
1. Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
Open this publication in new window or tab >>Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

One of the most important events in the history of life is the evolution of the complex, eukaryotic cell. The eukaryotes are complex organisms with membrane-bound intracellular structures, and they include a variety of both single-celled and multicellular organisms: plants, animals, fungi and various protists. The evolutionary origin of this group may be studied by direct evidence of past life: fossils. The oldest traces of eukaryotes have appeared by 2.4 billion years ago (Ga), and have additionally diversified in the period around 1.8 Ga. The Mesoproterozoic Era (1.6-1 Ga) is characterised by the first evidence of the appearance complex unicellular microfossils, as well as innovative morphologies, and the evolution of sexual reproduction and multicellularity. For a better understanding of the early eukaryotic evolution and diversification patterns, a part of this thesis has focused on the microfossil records from various time periods and geographic locations. Examination of microfossil morphology, cell wall microstructure and biochemical properties, reflect their intracellular complexity and function, and allow reconstructions of their life cycle, as well as observing the evolutionary pattern of change from Mesoproterozoic, to Cambrian-Ordovician transition. Several case studies included assemblages deriving from Mesoproterozoic, Neoproterozoic and early Paleozoic time intervals that show disparate morphotypes and innovative features indicative of algal clades. The Mesoproterozoic Ruyang Group in northern China has yielded a diverse microfossil assemblage that provides important clues about the diversification of different eukaryotic groups. Furthermore these microfossils contributed an additional evidence for the emergence of the crown group Eukarya by 1.7-1.4 Ga. In another part of this thesis, examination of wall microstructure and chemical properties via Raman spectroscopy has been used to assess the biological affinities of various Neoproterozoic problematic carbonaceous compression fossils. Studies on the early Phanerozoic (c. 545-485 Ma) assemblages from Estonia reconstructed patterns of the early radiations of phytoplankton and its evolutionary innovations. A continuing theme in this thesis has been using a combination of evidence of microfossils’ fine-scale morphology, ecology and chemical properties to determine their function in life, in addition to their systematic position.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 47 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1308
Keyword
microfossils, eukaryotes, Mesoproterozoic, Neoproterozoic, Cambrian, Ordovician, palaeobiology, biostratigraphy, phylogeny, China, Estonia, Siberian Platform, prasinophytes, microstructure, Raman spectroscopy
National Category
Geology
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
Identifiers
urn:nbn:se:uu:diva-265229 (URN)978-91-554-9389-9 (ISBN)
Public defence
2015-12-11, Hambergsalen, Geocentrum, Villavägen 16, 752 36, Uppsala, 10:15 (English)
Opponent
Supervisors
Projects
Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
Funder
Swedish Research Council, 621-2009-4445
Available from: 2015-11-19 Created: 2015-10-26 Last updated: 2016-01-13

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