The Avalon assemblage was the first of the three Late Ediacaran biotic assemblages, spanning from 575 Ma to 560 Ma. It was followed by the

White Sea assemblage The White Sea assemblage was the second of the three Late Ediacaran biotic assemblages, following the Avalon assemblage and preceding the Nama assemblage. It spanned from 560 Ma to 550 Ma. Showing an increase in genus diversity from the Aval ...

, although temporal overlaps have been noted between the biotic assemblages. While earlier macroscopic fossils, mostly of

algal Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular microalgae, s ...

origin, are known from the Lantian Formation, Avalon-type localities provide some of the first evidence of putative metazoan ancestors, as part of the

Ediacaran biota The Ediacaran (; formerly Vendian) biota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were enigmatic tubular and frond-shaped, mostly sessile, organis ...

Research history

The division of the Ediacaran biota in three separate assemblages was first postulated by Ben Waggoner in 2003.

Geography

Most Avalonian fossil sites are known from the central United Kingdom and eastern

Newfoundland Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of . As of 2025 the population ...

, historically connected as part of the

Avalonia Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent are terranes in parts of the eastern coast of North America: Atlantic Canada, and parts of the East Coast of the United States, East Coast of the ...

microcontinent. Outside of Avalonia proper, other sites have been identified as part of the Avalon assemblage, such as the Olenek Uplift in

Siberia Siberia ( ; , ) is an extensive geographical region comprising all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has formed a part of the sovereign territory of Russia and its predecessor states ...

, and Sekwi Brooke in the

Northwest Territories The Northwest Territories is a federal Provinces and territories of Canada, territory of Canada. At a land area of approximately and a 2021 census population of 41,070, it is the second-largest and the most populous of Provinces and territorie ...

of Canada.

Biota

Deep-water

rangeomorph The rangeomorphs are a group of Ediacaran Ediacaran biota, fossils. Ediacarans are the oldest large fossil organisms on earth, and many are not self-evidently related to anything else that has ever lived. However, some Ediacarans clearly resemble ...

s, and to a lesser extent arboreomorphs, dominated the Avalonian biota, although other macrofossil taxa are known. Certain clades typical of the

, such as

dipleurozoa Dipleurozoa (or Dickinsoniomorpha) are extinct proarticulate organisms of the Ediacaran period, which had a flat and more or less ovoid shape. Polychaete worms were treated, however it seems more likely that they were vendobionts. The most re ...

ns, are not known from Avalon assemblage sites, but only appear in the more recent shallow-water

. Nonetheless, the Avalon biota has been described as occupying the full range of morphologies that would later be present in the following assemblages.

References

{{reflist, refs= {{Cite journal , last1=Shen , first1=Bing , last2=Dong , first2=Lin , last3=Xiao , first3=Shuhai , last4=Kowalewski , first4=Michal , date=4 January 2008 , title=The Avalon explosion: evolution of Ediacara morphospace , url=https://pubmed.ncbi.nlm.nih.gov/18174439/ , journal=Science , volume=319 , issue=5859 , pages=81–84 , doi=10.1126/science.1150279 , issn=1095-9203 , pmid=18174439, bibcode=2008Sci...319...81S {{Cite journal , last1=Liu , first1=Alexander G. , last2=Kenchington , first2=Charlotte G. , last3=Mitchell , first3=Emily G. , date=June 2015 , title=Remarkable insights into the paleoecology of the Avalonian Ediacaran macrobiota , url=https://linkinghub.elsevier.com/retrieve/pii/S1342937X14003256 , journal=Gondwana Research , language=en , volume=27 , issue=4 , pages=1355–1380 , doi=10.1016/j.gr.2014.11.002, bibcode=2015GondR..27.1355L , hdl=1983/ef181134-4023-4747-8137-ed9da7a97771 , hdl-access=free {{Cite book , last1=Bottjer , first1=David J. , url=https://doi.org/10.1007/1-4020-5202-2_4 , title=Evolutionary Paleoecology of Ediacaran Benthic Marine Animals , last2=Clapham , first2=Matthew E. , date=2006 , publisher=Springer Netherlands , isbn=978-1-4020-5202-6 , editor-last=Xiao , editor-first=Shuhai , location=Dordrecht , pages=91–114 , language=en , doi=10.1007/1-4020-5202-2_4 , editor-last2=Kaufman , editor-first2=Alan J. {{Cite thesis , last=Liu , first=Alexander G. S. C. , title=Understanding the Ediacaran Assemblages of Avalonia: A Palaeoenvironmental, Taphonomic and Ontogenetic Study , date=2011 , access-date=2 April 2024 , degree=PhD , publisher=University of Oxford , url=https://ora.ox.ac.uk/objects/uuid:fe6e4dff-27d5-489e-bd9d-b1e299a4946c/files/m350e9bf27bda45f30281a4b7d2fac966 {{Cite journal , last=Waggoner , first=Ben , date=1 February 2003 , title=The Ediacaran Biotas in Space and Time , url=https://academic.oup.com/icb/article-lookup/doi/10.1093/icb/43.1.104 , journal=Integrative and Comparative Biology , language=en , volume=43 , issue=1 , pages=104–113 , doi=10.1093/icb/43.1.104 , pmid=21680415 , issn=1540-7063 {{Cite journal , last1=Narbonne , first1=Guy M. , last2=Laflamme , first2=Marc , last3=Trusler , first3=Peter W. , last4=Dalrymple , first4=Robert W. , last5=Greentree , first5=Carolyn , date=March 2014 , title=Deep-Water Ediacaran Fossils from Northwestern Canada: Taphonomy, Ecology, and Evolution , url=https://www.cambridge.org/core/product/identifier/S002233600005705X/type/journal_article , journal=Journal of Paleontology , language=en , volume=88 , issue=2 , pages=207–223 , doi=10.1666/13-053 , issn=0022-3360, url-access=subscription Ediacaran