title: Phosphatized polar lobe-forming embryos from the Precambrian of southwest China.
abstract: In developing embryos of some extant spiralian animals, polar lobe formation is one of the symmetry-breaking mechanisms for segregation of maternal cytoplasmic substances to certain blastomeres and not others. Polar lobe formation leads to unique early cleavage morphologies that include trilobed, J-shaped, and five-lobed structures. Fossil embryos similar to modern lobeforming embryos are recognized from the Precambrian Doushantuo Formation phosphates, Weng'an, Guizhou Province, China. These embryos are abundant and form a developmental sequence comparable to different developing stages observed in lobe-forming embryos of extant spiralians. These data imply that lobe formation is an evolutionarily ancient process of embryonic specification.
authors.affiliation: Nanjing Institute of Geology and Paleontology, Institute of Evo/Developmental Biology, and State Key Laboratory of Pharmaceutical Biotechnology, Nanjing University, Nanjing 210093, China. chenjy@nju.edu.cn
authors.forename: Jun-Yuan
authors.initials: JY
authors.lastname: Chen
authors.forename: David J
authors.initials: DJ
authors.lastname: Bottjer
authors.forename: Eric H
authors.initials: EH
authors.lastname: Davidson
authors.forename: Stephen Q
authors.initials: SQ
authors.lastname: Dornbos
authors.forename: Xiang
authors.initials: X
authors.lastname: Gao
authors.forename: Yong-Hua
authors.initials: YH
authors.lastname: Yang
authors.forename: Chia-Wei
authors.initials: CW
authors.lastname: Li
authors.forename: Gang
authors.initials: G
authors.lastname: Li
authors.forename: Xiu-Qiang
authors.initials: XQ
authors.lastname: Wang
authors.forename: Ding-Chang
authors.initials: DC
authors.lastname: Xian
authors.forename: Hung-Jen
authors.initials: HJ
authors.lastname: Wu
authors.forename: Yeu-Kuang
authors.initials: YK
authors.lastname: Hwu
authors.forename: Paul
authors.initials: P
authors.lastname: Tafforeau
mesh_terms: D000818:Animals; D000845:Annelida / Q000196:embryology; D005075:Biological Evolution; D001757:Blastomeres / Q000166:cytology; D002681:China; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology* / Q000166:cytology; D047108:Embryonic Development; D005580:Fossils; D019015:Geologic Sediments; D007448:Invertebrates / Q000196:embryology*; D008974:Mollusca / Q000196:embryology; D010710:Phosphates; D010986:Platyhelminths / Q000196:embryology
chemical_list: D010710:Phosphates