title: Cellular and subcellular structure of neoproterozoic animal embryos.
abstract: Stereoblastic embryos from the Doushantuo Formation of China exhibit occasional asynchronous cell division, with diminishing blastomere volume as cleavage proceeded. Asynchronous cell division is common in modern embryos, implying that sophisticated mechanisms for differential cell division timing and embryonic cell lineage differentiation evolved before 551 million years ago. Subcellular structures akin to organelles, coated yolk granules, or lipid vesicles occur in these embryos. Paired reniform structures within embryo cells may represent fossil evidence of cells about to undergo division. Embryos exhibit no evidence of epithelial organization, even in embryos composed of approximately 1000 cells. Many of these features are compatible with metazoans, but the absence of epithelialization is consistent only with a stem-metazoan affinity for Doushantuo embryos.
authors.affiliation: Department of Geology, Amherst College, Amherst, MA 01002, USA. jwhagadorn@amherst.edu
authors.forename: James W
authors.initials: JW
authors.lastname: Hagadorn
authors.forename: Shuhai
authors.initials: S
authors.lastname: Xiao
authors.forename: Philip C J
authors.initials: PC
authors.lastname: Donoghue
authors.forename: Stefan
authors.initials: S
authors.lastname: Bengtson
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Gostling
authors.forename: Maria
authors.initials: M
authors.lastname: Pawlowska
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Raff
authors.forename: Rudolf A
authors.initials: RA
authors.lastname: Raff
authors.forename: F Rudolf
authors.initials: FR
authors.lastname: Turner
authors.forename: Yin
authors.initials: Y
authors.lastname: Chongyu
authors.forename: Chuanming
authors.initials: C
authors.lastname: Zhou
authors.forename: Xunlai
authors.initials: X
authors.lastname: Yuan
authors.forename: Matthew B
authors.initials: MB
authors.lastname: McFeely
authors.forename: Marco
authors.initials: M
authors.lastname: Stampanoni
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Nealson
mesh_terms: D000818:Animals; D001757:Blastomeres / Q000166:cytology; D002455:Cell Division; D019070:Cell Lineage; D048430:Cell Shape; D002681:China; D004625:Embryo, Nonmammalian / Q000166:cytology* / Q000648:ultrastructure; D047108:Embryonic Development; D004848:Epithelium / Q000196:embryology; D005580:Fossils; D005775:Gastrula / Q000166:cytology / Q000648:ultrastructure; D007448:Invertebrates / Q000196:embryology*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D015388:Organelles / Q000648:ultrastructure; D014057:Tomography, X-Ray Computed