Complex embryos displaying bilaterian characters from Precambrian Doushantuo phosphate deposits, Weng'an, Guizhou, China.
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-microCT) 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.
Chen
Jun-Yuan
JY
LPS of Nanjing Institute of Geology and Paleontology, Institute of Evo/Developmental Biology, State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, China. chenjunyuan@163.net
Bottjer
David J
DJ
Li
Gang
G
Hadfield
Michael G
MG
Gao
Feng
F
Cameron
Andrew R
AR
Zhang
Chen-Yu
CY
Xian
Ding-Chang
DC
Tafforeau
Paul
P
Liao
Xin
X
Yin
Zong-Jun
ZJ
D000818:Animals; D002681:China; D004625:Embryo, Nonmammalian / Q000166:cytology*; D005580:Fossils; D007091:Image Processing, Computer-Assisted; D007448:Invertebrates / Q000033:anatomy & histology*; D010163:Paleontology; D013045:Species Specificity