ESTABLISHING BASELINES FOR EDIACARAN-STYLE TAPHONOMIC EXPERIMENTS – A NEW DECAY SERIES FOR SEA HARES (MOLLUSCA) AND SEA ANEMONES (CNIDARIA)

Understanding the processes and pathways that lead to soft tissue preservation can be used to constrain the paleobiology of extinct organisms. Of particular interest are the latest Neoproterozoic Ediacara biota, which have been variously suggested to represent either diploblastic or triploblastic organisms. In this study, we construct decay indices for the diploblastic sea anemone Condylactis gigantea, and the triploblastic sea hare Dolabella auricularia, as a first step towards using decay studies to constrain the biology and tissue labilities of Ediacaran fossils. Organisms (n=33 per species) were decayed in jars of artificial sea water and removed at set time intervals (3 per time interval). Semi-quantitative decay indices were then generated and used for comparison between species. D. auricularia persisted for an extended temporal range than C. gigantea and conserved body shape throughout decay, while C. gigantea diffused more rapidly into the surrounding water. Though C. gigantea progressed in a much more reliable rate, in both subjects decay progressed from the anterior towards the posterior or pedal regions. C. gigantea experienced longer conservation of tentacles than the rhinopores of D. auricularia, but both of these features experienced relatively rapid loss. These decay series provide a measure for the decay states of fossil cnidarians and soft bodied mollusks, and form a critical first step towards constraining the tissue labilities of the enigmatic Ediacara biota.