title: Ediacaran discs from South America: probable soft-bodied macrofossils unlock the paleogeography of the Clymene Ocean.
abstract: The origin, affinity and paleoecology of macrofossils of soft-bodied organisms of the terminal Ediacaran Period have been highly debated. Previous discoveries in South America are restricted to small shelly metazoans of the Nama Assemblage. Here we report for the first time the occurrence of discoidal structures from the Upper Ediacaran Cerro Negro Formation, La Providencia Group, Argentina. Specimens are preserved in tabular sandstones with microbially-induced sedimentary structures. Flute marks and linear scours at the base of the sandstone layers indicate deposition under high energy, episodic flows. Stratigraphic, sedimentologic, petrographic and taphonomic analyses indicate that the origin of these structures is not related to abiotic process. Preservational and morphological features, as invagination and the presence of radial grooves, indicate that they resemble typical morphs of the Aspidella plexus. The large number of small-sized individuals and the wide range of size classes with skewed distribution suggest that they lived in high-density communities. The presence of Aspidella in the Cerro Negro Formation would represent the first reliable record of Ediacaran soft-bodied organisms in South America. It also supports the paleogeographic scenario of the Clymene Ocean, in which a shallow sea covered part of the southwest Gondwana at the end of the Ediacaran.
authors.affiliation: Centro de Investigaciones Geológicas - CONICET - FCNyM (UNLP), Diagonal 113 N°275, La Plata, Argentina.
authors.forename: María Julia
authors.initials: MJ
authors.lastname: Arrouy
authors.affiliation: Departamento de Geologia Aplicada, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Avenida 24A, 1515, Rio Claro 13506-900, Brazil.
authors.forename: Lucas V
authors.initials: LV
authors.lastname: Warren
authors.affiliation: Departamento de Geologia Aplicada, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Avenida 24A, 1515, Rio Claro 13506-900, Brazil.|Curso de Geologia, Instituto de Geografia, Universidade Federal de Uberlândia, Rodovia LMG 746, Km 1, Monte Carmelo 38500-000, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Quaglio
authors.affiliation: Centro de Investigaciones Geológicas - CONICET - FCNyM (UNLP), Diagonal 113 N°275, La Plata, Argentina.
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Poiré
authors.affiliation: Departamento de Zoologia, Instituto de Biociências, Universidade Estadual Paulista, Distrito de Rubião Júnior, Botucatu 18618-000, Brazil.
authors.forename: Marcello Guimarães
authors.initials: MG
authors.lastname: Simões
authors.affiliation: Departamento de Geologia Aplicada, Instituto de Geociências e Ciências Exatas, Universidade Estadual Paulista, Avenida 24A, 1515, Rio Claro 13506-900, Brazil.
authors.forename: Milena Boselli
authors.initials: MB
authors.lastname: Rosa
authors.affiliation: Centro de Investigaciones Geológicas - CONICET - FCNyM (UNLP), Diagonal 113 N°275, La Plata, Argentina.
authors.forename: Lucía E Gómez
authors.initials: LE
authors.lastname: Peral
mesh_terms: D005075:Biological Evolution; D005580:Fossils / Q000033:anatomy & histology; D019015:Geologic Sediments; D010162:Paleography; D013020:South America