While earlier macroscopic fossils, mostly of algal 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.

[6] 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] Deep-water rangeomorphs, and to a lesser extent arboreomorphs, dominated the Avalonian biota, although other macrofossil taxa are known.

[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.