Doushantuo-type microfossils from latest Ediacaran phosphorites of northern Mongolia

Abstract

Phosphorites of the latest Ediacaran upper Khesen Formation in the Khuvsgul Group of northern Mongolia preserve a newly discovered, three-dimensionally phosphatized Doushantuo-type microfossil assemblage. Eight genera include the second occurrence of the putative multicellular fossil animal embryo Megasphaera outside South China, the Doushantuo-Pertatataka-type acanthomorphic acritarchs Appendisphaera, Cavaspina, and Variomargosphaeridium, and the possible alga Archaeophycus yunnanensis. The assemblage occurs in the lowermost phosphorite horizon in foreland basin deposits on the Khuvsgul terrane; lithostratigraphic and 13C correlation with the Zavkhan terrane of southwestern Mongolia establish a latest Ediacaran age for the fossiliferous phosphorites. Thus, this is the youngest Doushantuo-type assemblage yet reported. It extends the range of Megasphaera, filling a gap in the record of phosphatized embryo-like forms between the ~600 Ma Doushantuo Weng'an Biota and Cambrian examples. The Khesen fossil assemblage emphasizes the potential of Mongolian phosphorites to provide new paleontological data on the Ediacaran-Cambrian transition, and to resolve the phylogenetic debate surrounding Megasphaera embryo-like taxa. Response to Reviewers: Response to reviewer's comments Line 116. I believe that the specimens in Fig. 3B and 3C represent Cavasipna acuminata. They have too short and small processes to be Tanarium. We have removed the reference to Tanarium. However, our fossils most closely resemble Cavaspina basiconica from the Doushantuo Formation (Xiao et al., 2014, J. Paleo.) which has larger numbers of more densely packed processes and can reach

Early fossil record of Euarthropoda and the Cambrian Explosion

“…Some may even be nonbiological, as comparable structures can be generated during experimental precipitation of apatite (119). Other late Precambrian phosphate deposits contain a similar suite of single-celled/colonial eukarya and bacteria (81)(82)(83)117), and even in the Khesen Formation of Mongolia, which is immediately below the base of the Cambrian, no metazoan remains are found (120,121). The Doushantuo is continuous with the early Cambrian Meischucun phosphorites of South China, which preserve embryos and hatchlings of cnidarians (122).…”

Stratigraphy of the Khuvsgul Group, Mongolia

“…on Cryogenian Snowball Earth glaciations recorded by the diamictite units (Macdonald and Jones, 2011) and the late Ediacaran to Cambrian Doushantuo-Pertatanka-type microfossil assemblage within the phosphatic strata (Anderson et al, 2017;. Over the past half-century, workers have developed a variety of stratigraphic schemes for the Khuvsgul Group, with correlations to putatively equivalent units on the Siberian side of the Russian-Mongolian border (Osokin and Tyzhinov, 1998;Kuzmichev et al, 2001;Vishnevskaya and Letnikova, 2013), or the southwest margin of the Zavkhan terrane (Macdonald and Jones, 2011, Smith et al, 2016, Bold et al, 2016a.…”

New scientific direction of the bacterial paleontology in Mongolia

“…All kinds of microbes, including prokaryotes and eukaryotes and their symbiotic associations with each other and higher organisms, can contribute actively to geological phenomena, and central to many such geomicrobial processes are transformations of metals and minerals. Indeed a diverse Proterozoic-Phanerozoic sedimentary stratigraphic rocks in Mongolia record and faunal, floral, and also bacterial localities (Mitrofanov et al, 1981;Bat-Ireedui, 1991, Bosak et al, 2011a, b;Barsbold and Byamba, 2012;Byamba, 2012;Dorjnamjaa, 2016;Dorjnamjaa et al, 2016;Dorjnamjaa, 2017;Anderson et al, 2017aAnderson et al, , b, 2018. In Mongolia the oldest microorganisms from the Paleoproterozoic were found in the iron-bearing quartzite.…”