title: Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago.
abstract: The evidence for macroscopic life during the Palaeoproterozoic era (2.5-1.6 Gyr ago) is controversial. Except for the nearly 2-Gyr-old coil-shaped fossil Grypania spiralis, which may have been eukaryotic, evidence for morphological and taxonomic biodiversification of macroorganisms only occurs towards the beginning of the Mesoproterozoic era (1.6-1.0 Gyr). Here we report the discovery of centimetre-sized structures from the 2.1-Gyr-old black shales of the Palaeoproterozoic Francevillian B Formation in Gabon, which we interpret as highly organized and spatially discrete populations of colonial organisms. The structures are up to 12 cm in size and have characteristic shapes, with a simple but distinct ground pattern of flexible sheets and, usually, a permeating radial fabric. Geochemical analyses suggest that the sediments were deposited under an oxygenated water column. Carbon and sulphur isotopic data indicate that the structures were distinct biogenic objects, fossilized by pyritization early in the formation of the rock. The growth patterns deduced from the fossil morphologies suggest that the organisms showed cell-to-cell signalling and coordinated responses, as is commonly associated with multicellular organization. The Gabon fossils, occurring after the 2.45-2.32-Gyr increase in atmospheric oxygen concentration, may be seen as ancient representatives of multicellular life, which expanded so rapidly 1.5 Gyr later, in the Cambrian explosion.
authors.affiliation: Laboratoire HYDRASA, UMR 6269 CNRS-INSU, Université de Poitiers, 86022 Poitiers, France. abder.albani@univ-poitiers.fr
authors.forename: Abderrazak
authors.initials: A
authors.lastname: El Albani
authors.forename: Stefan
authors.initials: S
authors.lastname: Bengtson
authors.forename: Donald E
authors.initials: DE
authors.lastname: Canfield
authors.forename: Andrey
authors.initials: A
authors.lastname: Bekker
authors.forename: Roberto
authors.initials: R
authors.lastname: Macchiarelli
authors.forename: Arnaud
authors.initials: A
authors.lastname: Mazurier
authors.forename: Emma U
authors.initials: EU
authors.lastname: Hammarlund
authors.forename: Philippe
authors.initials: P
authors.lastname: Boulvais
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Dupuy
authors.forename: Claude
authors.initials: C
authors.lastname: Fontaine
authors.forename: Franz T
authors.initials: FT
authors.lastname: Fürsich
authors.forename: François
authors.initials: F
authors.lastname: Gauthier-Lafaye
authors.forename: Philippe
authors.initials: P
authors.lastname: Janvier
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Javaux
authors.forename: Frantz Ossa
authors.initials: FO
authors.lastname: Ossa
authors.forename: Anne-Catherine
authors.initials: AC
authors.lastname: Pierson-Wickmann
authors.forename: Armelle
authors.initials: A
authors.lastname: Riboulleau
authors.forename: Paul
authors.initials: P
authors.lastname: Sardini
authors.forename: Daniel
authors.initials: D
authors.lastname: Vachard
authors.forename: Martin
authors.initials: M
authors.lastname: Whitehouse
authors.forename: Alain
authors.initials: A
authors.lastname: Meunier
mesh_terms: D001419:Bacteria / Q000166:cytology; D017753:Ecosystem; D056890:Eukaryota / Q000166:cytology; D005580:Fossils; D005681:Gabon; D019015:Geologic Sediments / Q000382:microbiology; D049690:History, Ancient; D010100:Oxygen / Q000378:metabolism*
chemical_list: D010100:Oxygen