Phosphatized Polar Lobe-Forming Embryos from the Precambrian of Southwest China

doi:10.1126/science.1125964

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Phosphatized Polar Lobe-Forming Embryos from the Precambrian of Southwest China

Jun-Yuan Chen,¹^* David J. Bottjer,² Eric H. Davidson,³ Stephen Q. Dornbos,⁴ Xiang Gao,¹ Yong-Hua Yang,¹ Chia-Wei Li,⁵ Gang Li,⁶ Xiu-Qiang Wang,¹ Ding-Chang Xian,⁶ Hung-Jen Wu,⁵ Yeu-Kuang Hwu,⁷ Paul Tafforeau⁸^,9

In developing embryos of some extant spiralian animals, polarlobe formation is one of the symmetry-breaking mechanisms forsegregation of maternal cytoplasmic substances to certain blastomeresand not others. Polar lobe formation leads to unique early cleavagemorphologies that include trilobed, J-shaped, and five-lobedstructures. Fossil embryos similar to modern lobeforming embryosare recognized from the Precambrian Doushantuo Formation phosphates,Weng'an, Guizhou Province, China. These embryos are abundantand form a developmental sequence comparable to different developingstages observed in lobe-forming embryos of extant spiralians.These data imply that lobe formation is an evolutionarily ancientprocess of embryonic specification.

¹ Nanjing Institute of Geology and Paleontology, Institute of Evo/Developmental Biology, and State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, China.
² Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089, USA.
³ Division of Biology, 156-29, California Institute of Technology, Pasadena, CA 91125, USA.
⁴ Department of Geosciences, University of Wisconsin, Milwaukee, WI 53201, USA.
⁵ Department of Life Science, National Tsing Hua University, Hsinchu 300, Taiwan, China.
⁶ Institute of High Energy Physics, Beijing 100049, China.
⁷ Institute of Physics, Academia Sinica, Taipei, Taiwan, China.
⁸ European Synchrotron Radiation Facility, F-38043 Grenoble, France.
⁹ Laboratoire de Géobiologie, Biochronologie et Paléontologie Humaine, UMR CNRS 6046, F-86022 Poitiers, France.

^* To whom correspondence should be addressed. E-mail: chenjy{at}nju.edu.cn, chenjunyuan{at}163.net

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