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.
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
Jun-Yuan
JY
Chen
David J
DJ
Bottjer
Gang
G
Li
Michael G
MG
Hadfield
Feng
F
Gao
Andrew R
AR
Cameron
Chen-Yu
CY
Zhang
Ding-Chang
DC
Xian
Paul
P
Tafforeau
Xin
X
Liao
Zong-Jun
ZJ
Yin
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