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Cyst and operculum formation in Cambrian-Ordovician galeate acritarchs from Estonia: implications for the algal phylogeny and blooms in the early Paleozoic
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology. (ORIGINS AND EARLY DIVERSIFICATION OF PHOTOSYNTHETIC MICROBIOTA)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
University of Southern Denmark.
2014 (English)In: 4th International Palaeontological Congress Abstract Volume: The history of life: a view from the Southern Hemisphere, 2014, 913- p.Conference paper, Poster (Other academic)
Abstract [en]

Unicellular organic-walled microfossils have been recovered from the Cambrian Lükati Formation and the Tremadocian Varangu Formation exposed in northern Estonia. Due to a combination of main morphological and biochemical characters, mainly a) excystment opening, b) processes, c) acetolysis-  resistant vesicle wall, microfossils have been interpreted as reproductive cysts of green algae. Both microfossil assemblages reflect the evolutionary patterns though the early Palaeozoic: from the Cambrian radiation of morphologically innovative taxa to increase in diversity and more disparate Ordovician forms. Combined light transmitted and scanning electron microscopy on the Middle Cambrian to Tremadocian galeate plexus acritarchs CaldariolaPriscogalea and Stelliferidium, revealed exceptionally preserved morphological elements and rare structure among fossil and extant microbiota – an opening with operculum (lid) in reproductive cyst, in addition to lavish vesicle ornamentation and sculpture. Operculum formation model is reconstructed from fossils at different stages of operculum position and attachment. Comparative morphology shows strong similarity of galeates to the reproductive cysts of the extant algae of Dasycladales (Chlorophyta), where the lid covering the cyst opening is determined by an intrinsic lid-forming apparatus during the organism’s reproductive stage. Opercula in Cambro-Ordovician galeate acritarchs and Dasycladales may be considered a homologous character. Unique morphology of the operculum-bearing microbiota would have required a degree of intracellular sophistication for its development, suggesting advanced intracellular machinery present already in the early Palaeozoic phytoplankton. Additionally, a new species of minute, sphaeromorphic and aggregated eukaryotic microfossils is recorded. It possesses a vesicle wall with corrugated sculpture and perforated by nano-scale pores. These minute early Cambrian microfossils have diagnostic characters of prasinophyte algae.

Place, publisher, year, edition, pages
2014. 913- p.
National Category
Research subject
Earth Science with specialization in Historical Geology and Palaeontology
URN: urn:nbn:se:uu:diva-254218OAI: oai:DiVA.org:uu-254218DiVA: diva2:817609
4th International Palaeontological Congress, Mendoza, Argentina, September 28 - October 3, 2014
Swedish Research Council, 621-2012-1669
Available from: 2015-06-05 Created: 2015-06-05 Last updated: 2015-06-17Bibliographically approved

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