Modern mucociliary creeping trails and the bodyplans of Neoproterozoic trace-makers

The bulk of Neoproterozoic trace fossils can be interpreted as horizontal c reeping trails produced by minute vermiform organisms moving on or just ben eath the seafloor or under algal mats. We have investigated the formation o f trails by living cnidarians and platyhelminths that creep by cilia on muc us ribbons. These relatively simple metazoans produce trails that are simil ar in size and morphology to some Neoproterozoic traces, owing to the entra inment of sediment within their mucus trails. Thus a mucociliary locomotory system provides sufficient means to form some types of Neoproterozoic trac es. It follows that the body architectures of the Neoproterozoic trace-make rs may have been quite simple, though complex bodyplans are, of course, not ruled out. Thus, the use of Neoproterozoic trace fossils to constrain the time of origin of bilaterians or of any crown-group bilaterian taxon remain s questionable.