Editing Ediacaran (section)

== Biota ==
{{Main|Ediacaran biota}}
[[File:Archaeaspinus_fedonkini.jpg|thumb|left|''[[Archaeaspinus]]'', a representative of [[phylum]] [[Proarticulata]] which also includes ''[[Dickinsonia]]'', ''[[Karakhtia]]'' and numerous other organisms. They are members of the [[Ediacaran biota]].<ref name="book1">{{Cite book|url=https://books.google.com/books?id=KsFFIrJ8IxEC&dq=Archaeaspinus&pg=PA261|title=The Rise of Animals: Evolution and Diversification of the Kingdom Animalia|first1=Mikhail A.|last1=Fedonkin |first2=James G.|last2=Gehling |first3=Kathleen|last3=Grey|first4=Guy M.|last4=Narbonne|first5=Patricia|last5=Vickers-Rich |date=Mar 16, 2007|publisher=JHU Press|isbn=9780801886799|access-date=August 7, 2022|via=Google Books}}</ref>]]

The fossil record from most of the Ediacaran Period is sparse, as more easily fossilized hard-shelled animals did not evolve until the latest Ediacaran. The Ediacaran biota include the oldest definite [[multicellular organism]]s (with specialized tissues), the most common types of which resemble segmented worms, fronds, disks, or immobile bags. Among largely undisputed animals, ''[[Auroralumina]]'' and ''[[Haootia]]'' were [[cnidarian|cnidarians]], while ''[[Yilingia]]'' represented the motile [[Bilateria|bilaterians]].<ref>{{cite journal |last1=Dunn |first1=F. S. |last2=Kenchington |first2=C. G. |last3=Parry |first3=L. A. |last4=Clark |first4=J. W. |last5=Kendall |first5=R. S. |last6=Wilby |first6=P. R. |title=A crown-group cnidarian from the Ediacaran of Charnwood Forest, UK |journal=Nature Ecology & Evolution |date=25 July 2022 |volume=6 |issue=8 |pages=1095–1104 |doi=10.1038/s41559-022-01807-x |pmid=35879540 |pmc=9349040 |bibcode=2022NatEE...6.1095D }}</ref><ref>{{Cite journal |last1=McIlroy |first1=D. |last2=Pasinetti |first2=G. |last3=Pérez-Pinedo |first3=D. |last4=McKean |first4=C. |last5=Dufour |first5=S. C. |last6=Matthews |first6=J. J. |last7=Menon |first7=L. R. |last8=Nicholls |first8=R. |last9=Taylor |first9=R. S. |date=2024-08-30 |title=The Palaeobiology of Two Crown Group Cnidarians: Haootia quadriformis and Mamsetia manunis gen. et sp. nov. from the Ediacaran of Newfoundland, Canada |journal=Life |language=en |volume=14 |issue=9 |pages=1096 |doi=10.3390/life14091096 |doi-access=free |pmid=39337880 |bibcode=2024Life...14.1096M |issn=2075-1729 |pmc=11432848 }}</ref><ref>{{Cite journal |last1=Chen |first1=Zhe |last2=Zhou |first2=Chuanming |last3=Yuan |first3=Xunlai |last4=Xiao |first4=Shuhai |date=September 2019 |title=Death march of a segmented and trilobate bilaterian elucidates early animal evolution |url=https://www.nature.com/articles/s41586-019-1522-7 |journal=Nature |language=en |volume=573 |issue=7774 |pages=412–415 |doi=10.1038/s41586-019-1522-7 |pmid=31485079 |bibcode=2019Natur.573..412C |issn=1476-4687}}</ref> [[Sponge|Sponges]] recognisable as such also appeared, at latest, during the terminal Ediacaran, including ''[[Helicolocellus]]'', a likely non-biomineralizing sponge. <ref>{{Cite journal |last=Xiao |first=Shuhai |date=12 August 2020 |title=Ediacaran sponges, animal biomineralization, and skeletal reefs |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |language=en |volume=117 |issue=35 |pages=20997–20999 |bibcode=2020PNAS..11720997X |doi=10.1073/pnas.2014393117 |issn=0027-8424 |pmc=7474584 |pmid=32817471 |doi-access=free}}</ref><ref>{{Cite journal |last1=Wang |first1=Xiaopeng |last2=Liu |first2=Alexander G. |last3=Chen |first3=Zhe |last4=Wu |first4=Chengxi |last5=Liu |first5=Yarong |last6=Wan |first6=Bin |last7=Pang |first7=Ke |last8=Zhou |first8=Chuanming |last9=Yuan |first9=Xunlai |last10=Xiao |first10=Shuhai |date=June 2024 |title=A late-Ediacaran crown-group sponge animal |url=https://www.nature.com/articles/s41586-024-07520-y |journal=Nature |language=en |volume=630 |issue=8018 |pages=905–911 |doi=10.1038/s41586-024-07520-y |pmid=38839967 |bibcode=2024Natur.630..905W |issn=1476-4687}}</ref>

Other than these definitive animals, most members of the Ediacaran biota bear little resemblance to modern lifeforms, and their [[biological classification|relationship]] with even the immediately following lifeforms of the [[Cambrian explosion]] is rather difficult to interpret.<ref name="OnTheEveOfAnimalRadiation">{{cite journal |last1=Xiao |first1=Shuhai |last2=Laflamme |first2=Marc |date=January 2009 |title=On the eve of animal radiation: phylogeny, ecology and evolution of the Ediacara biota |url=https://www.sciencedirect.com/science/article/abs/pii/S0169534708003066 |journal=[[Trends in Ecology & Evolution]] |volume=24 |issue=1 |pages=31–40 |doi=10.1016/j.tree.2008.07.015 |pmid=18952316 |bibcode=2009TEcoE..24...31X |access-date=10 November 2022}}</ref><ref>{{cite journal |last1=Dunn |first1=Frances S. |last2=Liu |first2=Alexander G. |date=11 February 2019 |title=Viewing the Ediacaran biota as a failed experiment is unhelpful |url=https://www.nature.com/articles/s41559-019-0815-4#citeas |journal=[[Nature Ecology and Evolution]] |volume=3 |issue=4 |pages=512–514 |doi=10.1038/s41559-019-0815-4 |pmid=30742104 |bibcode=2019NatEE...3..512D |s2cid=59945361 |access-date=10 November 2022}}</ref> More than 100 [[List of Ediacaran genera|genera]] have been described, and well known forms include ''[[Arkarua]]'', ''[[Charnia]]'', ''[[Dickinsonia]]'', ''[[Ediacaria]]'', ''[[Marywadea]]'', ''[[Cephalonega]]'', ''[[Pteridinium]]'', and ''[[Yorgia]]''. However, despite the overall enigmaticness of most Ediacaran organisms, some fossils identifiable as hard-shelled agglutinated [[foraminifera]] (which are not classified as animals) are known from latest Ediacaran sediments of western Siberia.<ref>{{Cite journal|last1=Kontorovich|first1=A. E.|last2=Varlamov|first2=A. I.|last3=Grazhdankin|first3=D. V.|last4=Karlova|first4=G. A.|last5=Klets|first5=A. G.|last6=Kontorovich|first6=V. A.|last7=Saraev|first7=S. V.|last8=Terleev|first8=A. A.|last9=Belyaev|first9=S. Yu.|last10=Varaksina|first10=I. V.|last11=Efimov|first11=A. S.|date=2008-12-01|title=A section of Vendian in the east of West Siberian Plate (based on data from the Borehole Vostok 3)|url=http://www.sciencedirect.com/science/article/pii/S106879710800206X|journal=Russian Geology and Geophysics|language=en|volume=49|issue=12|pages=932–939|doi=10.1016/j.rgg.2008.06.012|bibcode=2008RuGG...49..932K|issn=1068-7971}}</ref>

Four different biotic intervals are known in the Ediacaran, each being characterised by the prominence of a unique ecology and faunal assemblage. The first spanned from 635 to around 575 Ma and was dominated by acritarchs known as [[large ornamented Ediacaran microfossil]]s.<ref name=Cohen2009>{{Cite journal | first1=P. A.| last2= Knoll| last3= Kodner | first2=A. H.| last1 = Cohen | first3=R. B.| journal = Proceedings of the National Academy of Sciences of the United States of America| volume = 106| title = Large spinose microfossils in Ediacaran rocks as resting stages of early animals| issue = 16| pages = 6519–6524| date=Apr 2009 | issn = 0027-8424| pmid = 19366668| pmc = 2672526| doi = 10.1073/pnas.0902322106 |bibcode = 2009PNAS..106.6519C | doi-access= free}}</ref> The second spanned from around 575 to 560 Ma and was characterised by the Avalon biota. The third spanned from 560 to 550 Ma; its biota has been dubbed the White Sea biota due to many fossils from this time being found along the coasts of the [[White Sea]]. The fourth lasted from 550 to 539 Ma and is known as the interval of the Nama biotic assemblage.<ref name="EvansEtAl2022">{{cite journal |last1=Evans |first1=Scott D. |last2=Tu |first2=Chenyi |last3=Rizzo |first3=Adriana |last4=Surprenant |first4=Rachel L. |last5=Boan |first5=Phillip C. |last6=McCandless |first6=Heather |last7=Marshall |first7=Nathan |last8=Xiao |first8=Shuhai |last9=Droser |first9=Mary L. |date=7 November 2022 |title=Environmental drivers of the first major animal extinction across the Ediacaran White Sea-Nama transition |url=https://www.researchgate.net/publication/365204103 |journal=[[Proceedings of the National Academy of Sciences of the United States of America]] |volume=119 |issue=46 |pages=e2207475119 |bibcode=2022PNAS..11907475E |doi=10.1073/pnas.2207475119 |doi-access=free |pmc=9674242 |pmid=36343248 |access-date=24 November 2023 |hdl=10919/112639}}</ref>

There is evidence for [[End-Ediacaran extinction|a mass extinction]] during this period from early animals changing the environment,<ref>{{Cite journal |last1=Laflamme |first1=Marc |last2=Darroch |first2=Simon A. F. |last3=Tweedt |first3=Sarah M. |last4=Peterson |first4=Kevin J. |last5=Erwin |first5=Douglas H. |date=1 March 2013 |title=The end of the Ediacara biota: Extinction, biotic replacement, or Cheshire Cat? |url=https://www.sciencedirect.com/science/article/pii/S1342937X1200353X |journal=[[Gondwana Research]] |series=Geological processes in the Early Earth |volume=23 |issue=2 |pages=558–573 |doi=10.1016/j.gr.2012.11.004 |bibcode=2013GondR..23..558L |issn=1342-937X |access-date=24 November 2023}}</ref> dating to the same time as the transition between the White Sea and the Nama-type biotas.<ref name="DarrochEtAl2015">{{cite journal |last1=Darroch |first1=Simon A. F. |last2=Sperling |first2=Erik A. |last3=Boag |first3=Thomas H. |last4=Racicot |first4=Rachel A. |last5=Mason |first5=Sara J. |last6=Morgan |first6=Alex S. |last7=Tweedt |first7=Sarah |last8=Myrow |first8=Paul |last9=Johnston |first9=David T. |last10=Erwin |first10=Douglas H. |last11=Laflamme |first11=Marc |date=7 September 2015 |title=Biotic replacement and mass extinction of the Ediacara biota |journal=[[Proceedings of the Royal Society B: Biological Sciences]] |volume=282 |issue=1814 |pages=1–10 |doi=10.1098/rspb.2015.1003 |pmc=4571692 |pmid=26336166|bibcode=2015RSPSB.28251003D }}</ref><ref>[https://www.sciencedaily.com/releases/2015/09/150902123456.htm Evidence that Earth's first mass extinction was caused by critters not catastrophe], ''[[ScienceDaily]]''</ref> Alternatively, this mass extinction has also been theorised to have been the result of an [[anoxic event]].<ref name="EvansEtAl2022" />