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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Carbonaceous and siliceous Neoproterozoic vase-shaped microfossils (Urucum Formation, Brazil) and the question of early protistan biomineralization

Texto completo
Autor(es):
Morais, Luana ; Fairchild, Thomas Rich ; Lahr, Daniel J. G. ; Rudnitzki, Isaac D. ; Schopf, J. William ; Garcia, Amanda K. ; Kudryavtsev, Anatoliy B. ; Romero, Guilherme R.
Número total de Autores: 8
Tipo de documento: Artigo de Revisão
Fonte: JOURNAL OF PALEONTOLOGY; v. 91, n. 3, p. 393-406, MAY 2017.
Citações Web of Science: 8
Resumo

Vase-shaped microfossils (VSMs) occur in dolomitic extraclasts of indeterminate provenance within the basal diamictite of the Neoproterozoic Urucum Formation (Jacadigo Group) of west-central Brazil, having an age constrained between 889 +/- 44 Ma (K-Ar; basement rocks) and 587 +/- 7 Ma (Ar-40/Ar-39 age of early metamorphic cryptomelane in overlying manganese ore). Early isopachous carbonate cement entombed these VSMs, preserving rare direct evidence of original wall composition that is carbonaceous (now kerogenous) in practically all specimens. Some tests are siliceous or composed of a quartz-kerogen mixture; secondary replacement explains some features of these tests, but original biomineralization seems more likely for others. This interpretation, coupled with test morphology, suggests affinity to arcellinid testate amoebae. Five VSM taxa are recognized in the deposit: Cycliocyrillium simplex Porter, Meisterfeld, and Knoll, 2003, and C. torquata Porter, Meisterfeld, and Knoll, 2003, originally described in the Chuar Group (USA), and three new monospecific genera-Palaeoamphora urucumense n. gen. n. sp., Limeta lageniformis n. gen. n. sp., and Taruma rata n. gen. n. sp. Most of the taxonomically important characteristics of these VSMs occur also in extant testate amoebae, but the combinations of some characters, such as organic-walled tests having exceptionally long necks that exhibit terminal apertures (L. lageniformis n. gen. n. sp.), are evidently novel additions to the known diversity of Neoproterozoic VSMs. Evidence of glacially influenced deposition in the conformably overlying Santa Cruz Formation may indicate that the Urucum Formation slightly preceded or was penecontemporaneous with a major Neoproterozoic glaciation, although the VSM-hosting extraclasts must be older, possibly rivaling the age of the testate amoebae of the Chichkan Formation (766 +/- 7 Ma) that are currently regarded as the oldest record of protists in the geological record. (AU)

Processo FAPESP: 13/04585-3 - Decifrando as grandes tendências de evolução molecular e morfológica nos Amoebozoa
Beneficiário:Daniel José Galafasse Lahr
Linha de fomento: Auxílio à Pesquisa - Apoio a Jovens Pesquisadores
Processo FAPESP: 13/12852-1 - Tafonomia e sistemática de microfósseis vasiformes neoproterozoicos do Brasil e seu significado paleoecológico e filogenético
Beneficiário:Luana Pereira Costa de Morais Soares
Linha de fomento: Bolsas no Brasil - Doutorado