Yeast fungi in the Ediacaran stromatolites of the Siberian Platform

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Yeast fungi are extremely diverse, very widespread, and have a long history of industrial use; however, the time of their origin and early ecology on Earth remain unclear. This work fills this gap in scientific research, and, for the first time, descriptions are given with the allocation of new taxa of discovered yeast fungi in the Ediacaran (635–538 Ma). They are perfectly preserved in the form of microfossils and participated in the development of silicified columnar stromatolites (reef-like organogenic formations). The rock material was collected from the Byuk Formation (about 550 Ma) in the Berezovsky trough in the east of the Siberian platform. It was studied in thin sections of stromatolites on a scanning electron microscope. Microfossils were studied using standard comparative morphological methods. Their biological interpretation and systematic identification were conducted using analogy, the most widespread and efficient method of scientific research. The fungal (yeast) nature of the microorganisms discovered is indicated by the following features: reproduction by budding, sporulation, and division of individuals (cells), and properties of cell growth and their ecology (parasitization on the green algae thalli). New taxa of fossil yeast fungi have been identified: genus Tungusia, type-species Tungisia mane. We suggest that these microorganisms were the early ancestors of the modern yeast fungi. Keywords: Tungusia, green algae, Ediacaran, Byuk Formation, Siberian platform.