Horizontal surface traces from the Fermeuse Formation, Ferryland (Newfoundland, Canada), and their place within the Late Ediacaran ichnological revolution

In recent years, multiple studies have emerged that claim to document metazoan locomotion within the late Ediacaran Period, between ~585 and 541 Ma. Most of this evidence is limited to simple horizontal burrows and surface trace fossils, but these have undergone little in the way of critical analysis to determine whether they truly result from metazoan activity. Here we review the evidence for metazoan locomotion from Avalonian biotic assemblages, and demonstrate that locomotory behaviour, largely in the form of horizontal surface trails, may not be as rare in those regions as has previously been considered. Furthermore, Avalonian trace fossils likely predate claims of metazoan locomotion from most other global localities. New evidence for horizontal surface traces from rocks of the Fermeuse Formation, ~560 Ma, is also presented. When discussed in the context of the global Ediacaran to Cambrian ichnofossil record, it becomes evident that a gradual increase in abundance of horizontal surface locomotion is observed through the late Ediacaran Period. Vertical movement within the sediment appears ~560 Ma, with evidence for organisms forming equilibrium traces in response to low levels of sediment input. Evidence for extensive vertical burrowing and pervasive bioturbation is not yet convincingly demonstrated until at or near the Ediacaran–Cambrian boundary, ~541 Ma.