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Subcellular structures in Ediacaran fossil cleavage embryos
Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
2008 (English)In: The Palaeontological Association: 52nd Annual Meeting 18th–21st December 2008, 2008Conference paper (Refereed)
Abstract [en]

The Ediacaran Doushantuo phosphoritic deposits in southern China hold exquisitely preserved microfossils, and a large number of papers on this biota have been published. The controversial cleavage embryos, preserved as diagenetically phosphatized replacements and encrustations, have been proposed to belong to animals, but no co-occurring adult forms have yet been identified. Recent studies, in which fossil embryos were analysed with synchrotron-radiation X-ray tomographic microscopy (srXTM), have shown that with this technique it is possible not only to distinguish between taphonomic and diagenetic features, but also to depict cellular and subcellular details of the internal structures. In this study, we describe some of the diversity of internal morphological features found in early-stage cleavage embryos by use of srXTM. A few exceptionally preserved 4-cell stage specimens exhibit subcellular structures indicative of eukaryotic affinity, such as complex nucleus-like structures, which are centrally located in each cell. One of these displays a spiral structure on the surface of each blastomere, suggesting affinity with Spiralicellula Xue et al. 1995. Other specimens display spheroidal and ovoidal structures interpreted as lipid vesicles or yolk granules. In 2007, Bailey et al. (Nature 445) published an alternative interpretation, in which they propose that the alleged cleavage fossils represent giant sulphur-oxidizing bacteria. However, recent decay studies of modern animal embryos in combination with the likely eukaryotic subcellular features described here supports the interpretation that these Ediacaran fossils from the Doushantuo Formation are in fact of embryonic nature.

Place, publisher, year, edition, pages
URN: urn:nbn:se:su:diva-16236OAI: diva2:182756
Available from: 2008-12-15 Created: 2008-12-15Bibliographically approved

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