LAUSR

Abstract The Ediacaran period saw the appearance of the first widespread ecosystems dominated by complex multicellular forms, with the earliest examples inhabiting deep waters below the photic zone. Contrary to expectation, the first appearance of large members of the Ediacara biota is sudden, and no definitive precursors have been described from earlier Neoproterozoic rocks; this sudden appearance has long been an enigma. Cryogenian fossils from deep-water deposits immediately pre-dating Marinoan glacial deposits within the Mackenzie Mountains, NW Canada, document the earliest stages of the growth of subphotic benthic communities. Among the previously described “Twitya discs” from this locality are at least two examples of the Ediacaran form-taxon Aspidella Billings, 1872. These fossils represent a nearly 80 Ma range extension of Aspidella and possible forerunners of the benthic communities of the Ediacara biota.