Biotic replacement and mass extinction of the Ediacara biota.
The latest Neoproterozoic extinction of the Ediacara biota has been variously attributed to catastrophic removal by perturbations to global geochemical cycles, 'biotic replacement' by Cambrian-type ecosystem engineers, and a taphonomic artefact. We perform the first critical test of the 'biotic replacement' hypothesis using combined palaeoecological and geochemical data collected from the youngest Ediacaran strata in southern Namibia. We find that, even after accounting for a variety of potential sampling and taphonomic biases, the Ediacaran assemblage preserved at Farm Swartpunt has significantly lower genus richness than older assemblages. Geochemical and sedimentological analyses confirm an oxygenated and non-restricted palaeoenvironment for fossil-bearing sediments, thus suggesting that oxygen stress and/or hypersalinity are unlikely to be responsible for the low diversity of communities preserved at Swartpunt. These combined analyses suggest depauperate communities characterized the latest Ediacaran and provide the first quantitative support for the biotic replacement model for the end of the Ediacara biota. Although more sites (especially those recording different palaeoenvironments) are undoubtedly needed, this study provides the first quantitative palaeoecological evidence to suggest that evolutionary innovation, ecosystem engineering and biological interactions may have ultimately caused the first mass extinction of complex life.
Smithsonian Institution, PO Box 37012, MRC 121, Washington, DC 20013-7012, USA Department of Earth and Environmental Sciences, Vanderbilt University, 2301 Vanderbilt Place, Nashville, TN 37235-1805, USA simon.a.darroch@vanderbilt.edu.
Simon A F
SA
Darroch
Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA Department of Geological Sciences, Stanford University, 450 Serra Mall Bldg. 320, Stanford, CA 94305, USA.
Erik A
EA
Sperling
Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3356 Mississauga Road, Ontario, Canada L5 L 1C6.
Thomas H
TH
Boag
Department of Biology, Howard University, 415 College Street NW, Washington, DC 20059, USA.
Rachel A
RA
Racicot
Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3356 Mississauga Road, Ontario, Canada L5 L 1C6.
Sara J
SJ
Mason
Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA.
Alex S
AS
Morgan
Smithsonian Institution, PO Box 37012, MRC 121, Washington, DC 20013-7012, USA Department of Behavior, Ecology, Evolution & Systematics, University of Maryland, College Park, MD 20742, USA.
Sarah
S
Tweedt
Geology Department, Colorado College, 14 E. Cache La Poudre, Colorado Springs, CO 80903, USA.
Paul
P
Myrow
Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA.
David T
DT
Johnston
Smithsonian Institution, PO Box 37012, MRC 121, Washington, DC 20013-7012, USA.
Douglas H
DH
Erwin
Department of Chemical and Physical Sciences, University of Toronto Mississauga, 3356 Mississauga Road, Ontario, Canada L5 L 1C6.
Marc
M
Laflamme
D044822:Biodiversity; D005075:Biological Evolution; D058448:Biota; D017753:Ecosystem; D053476:Extinction, Biological; D005580:Fossils; D019015:Geologic Sediments / Q000737:chemistry; D009276:Namibia; D010163:Paleontology
Cambrian; Ediacaran; diversity; ecology; ecosystem engineers; extinction