Complex embryos displaying bilaterian characters from Precambrian Doushantuo phosphate deposits, Weng'an, Guizhou, China

doi:10.1073/pnas.0904805106

Complex embryos displaying bilaterian characters from Precambrian Doushantuo phosphate deposits, Weng'an, Guizhou, China

^aLPS of Nanjing Institute of Geology and Paleontology, Institute of Evo/Developmental Biology, and State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, China;
^bDepartment of Earth Sciences, University of Southern California, Los Angeles, CA 90089;
^cInstitute of High Energy Physics, Beijing 100049, China;
^dKewalo Marine Laboratory, University of Hawaii at Manoa, Honolulu, HI 96813;
^eDivision of Biology, 156-29, California Institute of Technology, Pasadena, CA 91125; and
^fEuropean Synchrotron Radiation Facility, F-38043 Grenoble, France

Edited by J. William Schopf, University of California, Los Angeles, CA, and approved September 18, 2009 (received for review May 5, 2009)

Abstract

Three-dimensionally preserved embryos from the Precambrian Ediacaran Doushantuo Formation, Weng'an, Guizhou, southern China, have attracted great attention as the oldest fossil evidence yet found for multicellular animal life on Earth. Many embryos are early cleavage embryos and most of them yield a limited phylogenetic signal. Here we report the discovery of two Doushantuo embryos that are three-dimensionally preserved and complex. Imaging techniques using propagation phase-contrast based synchrotron radiation microtomography (PPC-SR-μCT) reveal that the organization of cells demonstrates several bilaterian features, including the formation of anterior-posterior, dorso-ventral, and right-left polarities, and cell differentiation. Unexpectedly, our observations show a noticeable difference in organization patterns between the embryos, suggesting that they represent two distinct taxa. These embryos provide further evidence for the presence of bilaterian animals in the Doushantuo biota. Furthermore, these bilaterians had already diverged into distantly related groups at least 40 million years before the Cambrian radiation, indicating that the last common ancestor of the bilaterians lived much earlier than is usually thought.

Footnotes

¹To whom correspondence should be addressed. E-mail: chenjunyuan{at}163.net
Author contributions: J.-Y.C., D.J.B., and M.G.H. designed research; J.-Y.C., G.L., F.G., A.R.C., C.-Y.Z., D.-C.X., X.L., and Z.-J.Y. performed research; G.L., F.G., and P.T. analyzed data; and J.-Y.C., D.J.B., and M.G.H. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0904805106/DCSupplemental.