The Avalon assemblage was the first of the three
Late Ediacaran biotic assemblages, spanning from
c. 575
Ma to
c. 560 Ma. It was followed by the
White Sea assemblage, although temporal overlaps have been noted between the biotic assemblages. While earlier macroscopic fossils, mostly of
algal origin, are known from the
Lantian Formation, Avalon-type localities provide the first evidence of putative metazoan ancestors, as part of the
Ediacaran biota.[1][3][4][5]
Research history
The division of the Ediacaran biota in three separate assemblages was first postulated by Ben Waggoner in 2003.[6]
Geography
Most Avalonian fossil sites are known from the central United Kingdom and eastern
Newfoundland, historically connected as part of the
Avalonia microcontinent.[3] Outside of Avalonia proper, other sites have been identified as part of the Avalon assemblage, such as the
Olenek Uplift in
Siberia, and
Sekwi Brooke in the
Northwest Territories of Canada.[7]
Biota
Deep-water
rangeomorphs, and to a lesser extent
arboreomorphs, dominated the Avalonian biota, although other macrofossil taxa are known. Certain clades typical of the
Ediacaran biota, such as
dipleurozoans, are not known from Avalon assemblage sites, but only appear in the more recent shallow-water
White Sea assemblage.[3][7] Nonetheless, the Avalon biota has been described as occupying the full range of morphologies that would later be present in the following assemblages.[1]