Taphomorphs within the Ediacaran Biota of Avalonia:  an Explanation of Ivesheadia and Related Forms  

One of the most problematic factors in interpreting the Ediacara biota is that of recognising the influence of preservational styles and post-mortem changes upon the morphology and taxonomy of these organisms.  We have observed bedding planes in both the Charnwood and Newfoundland regions of Avalonia that we consider to contain several taphomorphs of a single taxon on the same surface.  We consider that these taphomorphs demonstrate a taphonomic spectrum, ranging from finely preserved specimens of organisms such as Fractofusus and Charnia, through progressively more decayed stages, to effaced taphomorphs such as Ivesheadia.

This research explores the hypothesis that saprophytic microbial degradation of Ediacaran organisms on the palaeo-seafloor prior to burial by event beds can explain both this taphonomic spectrum, and the ‘effaced’ appearance of several key Avalonian taxa, such as Ivesheadia, Shepshedia and Blackbrookia. We argue that these important fossils may merely represent taphomorphs of other, more widespread Ediacaran taxa.  This suggestion, if accepted, would have significant implications for the palaeoecology of the earliest macrobiotic ecosystems, and for the proposed diversity of the Ediacaran biota.