Discovery of White Sea assemblage fossils from Laurentia.

Abstract

The dawn of animal life is preserved by fossils of the Ediacara Biota, which have been separated into three biotic assemblages: the Avalon, White Sea, and Nama. Geographic and temporal isolation of these faunas leads to uncertainties regarding patterns of change. We report the discovery of unambiguous fossil communities belonging to the White Sea assemblage from the paleocontinent of Laurentia in the Blueflower Formation, Mackenzie Mountains, Canada. Unlike previous localities, sedimentological and geochronological evidence supports an older origin and deeper-water setting for this assemblage, including the oldest motile bilaterians. Fossil communities overlap temporally with the Avalon assemblage and are recognized in similar deep-water paleoenvironments. These results provide support for a hypothesized pattern of offshore origination followed by habitation of shallower environments through time, potentially unique to the early radiation of animals.