EDIACARAN-STYLE DECAY EXPERIMENTS WITH ANEMONES AND SEA HARES

The latest Neoproterozoic Ediacara biota represents the first radiation of complex life. However, both their biological affinities and mode of preservation remain the subject of considerable debate. We perform a series of decay experiments on two architecturally simple, soft-bodied organisms—the diploblastic sea anemone Condylactis gigantea, and the triploblastic sea hare Dolabella auricularia, in order to address the following outstanding questions: (1) Do Ediacaran-style taphonomic scenarios affect the ‘normal’ (i.e., open marine) pattern and rate of decay?, (2) Do equivalent FeS ‘death masks’ form with both triploblastic and diploblastic organisms?, (3) Are the dark decay ‘halos’ that formed in the Darroch et al. (2012) experiments consistently associated with the precipitation of aluminosilicate or FeS mineral elements?, and (4) What is the relative importance of FeS vs. clay minerals in molding the external morphology of carcasses, and thus in fossil preservation?. We find that while rates are decreased, patterns of character loss remain consistent regardless of decay environment. Our results indicate that labile tissues tend to decay faster than the rate of precipitation of FeS or aluminosilicate minerals, and that these dark ‘halos’ possibly represent diffusion of organics. Implications of these results are that Ediacaran tissues may have been less labile than previously understood, exhibiting a preservational bias against specific cnidarian and molluscan characters—affinities previously determined for some Ediacarans. Our study provides evidence for the likelihood of both diploblastic and triploblastic organisms during this time.