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Science 13 October 2006:
Vol. 314. no. 5797, pp. 291 - 294
DOI: 10.1126/science.1133129
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Reports

Cellular and Subcellular Structure of Neoproterozoic Animal Embryos

James W. Hagadorn,1* Shuhai Xiao,2 Philip C. J. Donoghue,3 Stefan Bengtson,4 Neil J. Gostling,3 Maria Pawlowska,3 Elizabeth C. Raff,5,6 Rudolf A. Raff,5,6 F. Rudolf Turner,5 Yin Chongyu,7 Chuanming Zhou,8 Xunlai Yuan,8 Matthew B. McFeely,1 Marco Stampanoni,9 Kenneth H. Nealson10

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 551 million years ago. Subcellular structures akin to organelles, coated yolk granules, or lipid vesicles occur in these embryos. Paired reniform structures within embryo cells may represent fossil evidence of cells about to undergo division. Embryos exhibit no evidence of epithelial organization, even in embryos composed of ~1000 cells. Many of these features are compatible with metazoans, but the absence of epithelialization is consistent only with a stem-metazoan affinity for Doushantuo embryos.

1 Department of Geology, Amherst College, Amherst, MA 01002, USA.
2 Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
3 Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK.
4 Department of Palaeozoology, Swedish Museum of Natural History, SE-104 05 Stockholm, Sweden.
5 Department of Biology, Indiana University, Bloomington, IN 47401, USA.
6 School of Biological Sciences, University of Sydney, Sydney 2006, Australia.
7 Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China.
8 State Key Laboratory of Paleobiology and Stratigraphy, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing 210008, China.
9 Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen, Switzerland.
10 Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA.

* To whom correspondence should be addressed. E-mail: jwhagadorn{at}amherst.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)