Ediacaran Remains Below the 580 Ma Gaskiers Diamictite, Newfoundland, Canada

The Ediacara biota records the appearance and diversification of Earth’s first large, soft-bodied eukaryotes, including taxa interpreted as the oldest animals, yet their evolutionary origins remain unresolved. Previously, the oldest-known large (centimeter- to meter-scale) Ediacara-type macrofossils were 571-million-year-old fronds and other soft-bodied taxa from the upper Drook Formation at Mistaken Point in Newfoundland, Canada. Here we report macrofossil remains from deep-water, glaciogenically influenced strata of the Mall Bay Formation at two sites on the Colinet Islands, Newfoundland. These remains, radioisotopically dated at 580 Ma, are stratigraphically below the Gaskiers diamictite and over a kilometer lower than previously known taxa. These structures include simple discoidal remains from Little Colinet Island similar to the Ediacaran form-genus Aspidella, and abundant tubular structures, herein termed “Colinet structures” and described as Colinetia daltonensis gen. et sp. nov., from Great Colinet Island. Colinet structures are bipartite forms consisting of a centimeter-scale disc attached to an unbranched, clay-lined, decimeter- to meter-long, cylindrical tube that is preserved horizontally within the bedding surface. The tube contains an inner tube (tube-in-tube morphology) and maintains a consistent diameter along its length and also among different specimens in the assemblage. They exhibit features consistent with a biological reconstruction as open cylindrical tubes that were at least partly infaunal, with post-mortem fill by sediment injection guided by the horizontally oriented tubes. Colinet structures differ from previously described Ediacaran macrofossils in their taxonomy and preservation but morphologically resemble the basal parts of younger Ediacaran fronds and tubular organisms, suggesting a possible evolutionary affinity.