End-Ediacaran extinction
The end-Ediacaran extinction is a mass extinction believed to have occurred near the end of the
Evidence
Biotic evidence
Ediacaran organisms
During the Ediacaran period, two main groups of organisms are found in the fossil record: the "
Additionally, the late Ediacaran saw a faunal turnover between the White Sea biota, which lived between 560 and 550 million years ago, and the Nama biota, which lived between 550 and 539 million years ago.[5] The transition from the White Sea to the Nama biota saw a major reduction in diversity that was not recovered during the interval of the depauperate Nama biota, which has been attributed to either increased biological competition[1] or an anoxic event[5] and in either case suggests that large-scale extinction began well before the boundary between the Ediacaran and Cambrian.
Post-Ediacaran survivors
The fossil record of the earliest Cambrian, just after the Ediacaran period, shows a sudden increase in burrowing activity and diversity. However, the Cambrian explosion of animals that gave rise to body fossils did not happen instantaneously. This implies that the "explosion" did not represent animals "replacing" the incumbent organisms, and pushing them gradually to extinction; rather, the data are more consistent with a radiation of animals to fill in vacant niches, left empty as an extinction cleared out the pre-existing fauna.[6]
The theory that all Ediacarans became extinct at the start of the Cambrian is disproven if any post-Ediacaran survivors are found. Organisms from the lower Cambrian, such as
Some organisms clearly survived the extinction since life on Earth has continued. However, very few organisms are known from both sides of the Ediacaran-Cambrian boundary. One such organism is the agglutinated foraminifera Platysolenites.[10] Swartpuntia is one well known late Ediacaran vendobiont, which survived into the earliest Cambrian.[11] Cambrian Erytholus is a similar sandstone cast to Ediacaran Ventogyrus.[12] Ordovician and Silurian Rutgersella[13] and Devonian Protonympha[14] have been interpreted as surviving vendobionts, comparable with Ediacaran Dickinsonia and Spriggina, respectively.
Geochemical evidence
Negative δ13C excursions—geochemical signals often associated with mass extinctions—are observed during the Late Ediacaran. The Shuram excursion occurred around the same time as the boundary between the White Sea and Nama assemblages.[15] Another major negative carbon isotope excursion is known to have occurred at the end of the Ediacaran period and the beginning of the Cambrian.[16]
Sedimentary evidence
The transition between the White Sea and Nama biotas near the end of the Ediacaran is reflected in the geological record by an increase in
References
- ^ PMID 26336166.
- ^ ISSN 0091-7613.
- ^ "Stratigraphic Chart 2022" (PDF). International Stratigraphic Commission. February 2022. Retrieved 25 April 2022.
- S2CID 85623607.
- ^ PMID 36343248.
- ^ S2CID 4425120.
- S2CID 130602154.
- ^ See Ediacaria
- OCLC 156823511
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- doi:10.1111/let12253 (inactive 31 January 2024).)
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- .
- ^ S2CID 18376742.
- .
- ^ "What caused the mass extinction of Earth's first animals? Unravelling mystery of the Ediacaran-Cambrian transition". ScienceDaily. Retrieved 20 February 2020.
- S2CID 134663328. Retrieved 17 December 2022.