Ichnological evidence for meiofaunal bilaterians from the terminal Ediacaran and earliest Cambrian of Brazil.

Autor: Parry LA; Palaeobiology, Royal Ontario Museum, 100 Queen's Park, Toronto, Ontario, M5S 2C6, Canada. lparry@rom.on.ca.; Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, M5S 3B2, Canada. lparry@rom.on.ca., Boggiani PC; Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, 05508-080, São Paulo, Brazil., Condon DJ; NERC Isotope Geosciences Laboratory, British Geological Survey, Keyworth, Nottinghamshire, NG12 5GG, UK., Garwood RJ; School of Earth and Environmental Sciences, University of Manchester, Manchester, M13 9PL, UK.; Department of Earth Sciences, Natural History Museum, Cromwell Road, London, SW7 5BD, UK., Leme JM; Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, 05508-080, São Paulo, Brazil., McIlroy D; Department of Earth Sciences, Memorial University of Newfoundland, Alexander Murray Building, 300 Prince Philip Drive, St. John's, Newfoundland and Labrador, A1B 3X5, Canada., Brasier MD; Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, UK., Trindade R; Departamento de Geofisica, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão 1226, 05508-900, São Paulo, Brazil., Campanha GAC; Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, 05508-080, São Paulo, Brazil., Pacheco MLAF; Department of Biology, Federal University of São Carlos. Rodovia João Leme dos Santos - Parque Reserva Fazenda Imperial, Km 104, 18052780, Sorocaba, Brazil., Diniz CQC; Instituto de Geociências, Universidade de São Paulo, Rua do Lago, 562, 05508-080, São Paulo, Brazil., Liu AG; Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EQ, UK.
Jazyk: angličtina
Zdroj: Nature ecology & evolution [Nat Ecol Evol] 2017 Oct; Vol. 1 (10), pp. 1455-1464. Date of Electronic Publication: 2017 Sep 11.
DOI: 10.1038/s41559-017-0301-9
Abstrakt: The evolutionary events during the Ediacaran-Cambrian transition (~541 Myr ago) are unparalleled in Earth history. The fossil record suggests that most extant animal phyla appeared in a geologically brief interval, with the oldest unequivocal bilaterian body fossils found in the Early Cambrian. Molecular clocks and biomarkers provide independent estimates for the timing of animal origins, and both suggest a cryptic Neoproterozoic history for Metazoa that extends considerably beyond the Cambrian fossil record. We report an assemblage of ichnofossils from Ediacaran-Cambrian siltstones in Brazil, alongside U-Pb radioisotopic dates that constrain the age of the oldest specimens to 555-542 Myr. X-ray microtomography reveals three-dimensionally preserved traces ranging from 50 to 600 μm in diameter, indicative of small-bodied, meiofaunal tracemakers. Burrow morphologies suggest they were created by a nematoid-like organism that used undulating locomotion to move through the sediment. This assemblage demonstrates animal-sediment interactions in the latest Ediacaran period, and provides the oldest known fossil evidence for meiofaunal bilaterians. Our discovery highlights meiofaunal ichnofossils as a hitherto unexplored window for tracking animal evolution in deep time, and reveals that both meiofaunal and macrofaunal bilaterians began to explore infaunal niches during the late Ediacaran.
Databáze: MEDLINE
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