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Diversity of organic-walled microfossils from the early Mesoproterozoic Ruyang Group, North China Craton - a window into the early eukaryote evolution
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. (Origins And Early Diversification Of Photosynthetic Microbiota)
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Paleobiologi. (Origins And Early Diversification Of Photosynthetic Microbiota)
Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences.
2017 (Engelska)Ingår i: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, s. 101-130Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Mesoproterozoic Era was an important time for the initial diversification of eukaryotic groups and the appearance of the first complex morphologies. While eukaryotes evolved around 2.4 Ga, the first microfossils with ornamentation and sculpture occur in the 1.8-1.6 Ga successions worldwide. Shales and siltstones of the Ruyang Group, Shanxi Province, North China Craton, record a high diversity of such organic-walled microfossils. Recently, the depositional ages of this succession has been constrained to 1.75-1.40 Ga via   zircon U-Pb dating. This dating extends back the time of the first appearance of complex eukaryotic characters (e.g. processes, complex wall structure) in the fossil record. We have conducted a biostratigraphic investigation on of the samples throughout the fossiliferous Ruyang Group to provide an estimate of the early eukaryotic diversity in the Mesoproterozoic. Light- and scanning electron microscope studies have documented 26 species, including several that are reported for the first time, and some that were previously known only from younger, Neoproterozoic strata. Fossil diversity is high in the upper Baicaoping Formation, declines in the middle and reaches its peak in the upper Beidajian Formation. Novel morphologies among the unicellular Ruyang biota include a variety of processes, from tube-like extensions to hirsute spines, vesicles with velutinous outer membranes, as well as numerous specimens with internal bodies of varying sizes. We have also recorded the globally distributed Mesoproterozoic taxa Dictyosphaera, Shuiyousphaeridium, and Tappania. Key characters displayed by the Ruyang biota are consistent with reproductive structures (especially cysts among modern protists. These microfossils provide an additional evidence for the emergence of the crown group Eukarya by 1.7-1.4 Ga.

Ort, förlag, år, upplaga, sidor
2017. s. 101-130
Nyckelord [en]
Mesoproterozoic, Ruyang Group, organic-walled microfossils, eukaryotic evolution, North China, Dictyosphaera.
Nationell ämneskategori
Naturvetenskap Geologi
Forskningsämne
Geovetenskap med inriktning mot historisk geologi och paleontologi
Identifikatorer
URN: urn:nbn:se:uu:diva-265216DOI: 10.1016/j.precamres.2017.04.042ISI: 000404697200006OAI: oai:DiVA.org:uu-265216DiVA, id: diva2:864110
Projekt
Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
Forskningsfinansiär
Vetenskapsrådet, 621-2009-4445Tillgänglig från: 2015-10-25 Skapad: 2015-10-25 Senast uppdaterad: 2018-02-22Bibliografiskt granskad
Ingår i avhandling
1. Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
Öppna denna publikation i ny flik eller fönster >>Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
2015 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2015. s. 47
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1308
Nyckelord
microfossils, eukaryotes, Mesoproterozoic, Neoproterozoic, Cambrian, Ordovician, palaeobiology, biostratigraphy, phylogeny, China, Estonia, Siberian Platform, prasinophytes, microstructure, Raman spectroscopy
Nationell ämneskategori
Geologi
Forskningsämne
Geovetenskap med inriktning mot historisk geologi och paleontologi
Identifikatorer
urn:nbn:se:uu:diva-265229 (URN)978-91-554-9389-9 (ISBN)
Disputation
2015-12-11, Hambergsalen, Geocentrum, Villavägen 16, 752 36, Uppsala, 10:15 (Engelska)
Opponent
Handledare
Projekt
Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
Forskningsfinansiär
Vetenskapsrådet, 621-2009-4445
Tillgänglig från: 2015-11-19 Skapad: 2015-10-26 Senast uppdaterad: 2016-01-13

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