Xunlai Yuan

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Phosphatized microfossils in the Ediacaran (635-542 Myr ago) Doushantuo Formation, south China, have been interpreted as the embryos of early animals. Despite experimental demonstration that embryos can be preserved, microstructural evidence that the Doushantuo remains are embryonic and an unambiguous record of fossil embryos in Lower Cambrian rocks,(More)
Stereoblastic embryos from the Doushantuo Formation of China exhibit occasional asynchronous cell division, with diminishing blastomere volume as cleavage proceeded. Asynchronous cell division is common in modern embryos, implying that sophisticated mechanisms for differential cell division timing and embryonic cell lineage differentiation evolved before(More)
The deep-water Avalon biota (about 579 to 565 million years old) is often regarded as the earliest-known fossil assemblage with macroscopic and morphologically complex life forms. It has been proposed that the rise of the Avalon biota was triggered by the oxygenation of mid-Ediacaran deep oceans. Here we report a diverse assemblage of morphologically(More)
Bailey et al. propose that the Ediacaran microfossils Megasphaera and Parapandorina, previously interpreted as animal resting eggs and blastula embryos, represent Thiomargarita-like sulphide-oxidizing bacteria, claiming that this interpretation better explains their abundance and taphonomy. Here we highlight important observations that significantly weaken(More)
Ediacara fossils are central to our understanding of animal evolution on the eve of the Cambrian explosion, because some of them likely represent stem-group marine animals. However, some of the iconic Ediacara fossils have also been interpreted as terrestrial lichens or microbial colonies. Our ability to test these hypotheses is limited by a taphonomic bias(More)
Phosphorites of the Ediacaran Doushantuo Formation (∼600 million years old) yield spheroidal microfossils with a palintomic cell cleavage pattern. These fossils have been variously interpreted as sulphur-oxidizing bacteria, unicellular protists, mesomycetozoean-like holozoans, green algae akin to Volvox, and blastula embryos of early metazoans or bilaterian(More)
The Neoproterozoic Quruqtagh Group in the Tarim Block, NW China, contains multiple diamictites in the Bayisi, Altungol, Tereeken, and Hankalchough formations. These diamictites may represent three or possibly four discrete glaciations, although evidence for a glacial origin of the Bayisi and Altungol diamictite is ambiguous. To constrain their age and(More)
Abundant graphite particles occur in amphibolite-grade quartzite of the Archean-Paleoproterozoic Wutai Metamorphic Complex in the Wutaishan area of North China. Petrographic thin section observations suggest that the graphite particles occur within and between quartzite clasts and are heterogeneous in origin. Using HF maceration techniques, the Wutai(More)
Morphology-based phylogenetic analyses support the monophyly of the Scalidophora (Kinorhyncha, Loricifera, Priapulida) and Nematoida (Nematoda, Nematomorpha), together constituting the monophyletic Cycloneuralia that is the sister group of the Panarthropoda. Kinorhynchs are unique among living cycloneuralians in having a segmented body with repeated(More)