Diversity of organic-walled microfossils from the early Mesoproterozoic Ruyang Group, North China Craton - a window into the early eukaryote evolution
(English)Manuscript (preprint) (Other academic)
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.
Mesoproterozoic, Ruyang Group, organic-walled microfossils, eukaryotic evolution, North China, Dictyosphaera.
Natural Sciences Geology
Research subject Earth Science with specialization in Historical Geology and Palaeontology
IdentifiersURN: urn:nbn:se:uu:diva-265216OAI: oai:DiVA.org:uu-265216DiVA: diva2:864110
ProjectsPalaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes
FunderSwedish Research Council, 621-2009-4445