A BIOMECHANICAL APPROACH TO EDIACARAN HYPOTHESES - HOW TO WEED THE GARDEN OF EDIACARA

Flume experiments and analytical approaches are undertaken to determin e the stability of flat-lying Ediacaran organisms in fluid flow. Organ isms such as Dickinsonia would not have been viable if reconstructed a s free-living worms or syncytia. Models of flat-lying Ediacarans occup ying a range of densities well beyond those of suggested modern analog s were dislodged by fluid flow taken as typical of Ediacaran paleoenvi ronments. Analytical rests suggest that parameters such as thickness o f the organism and its coefficient of friction have little effect over the range of flows being considered here. These results lead to four non-exclusive interpretations of fossils of flat-lying Ediacarans: (1) The organisms have been transported from a quieter environment (in wh ich case their pristine preservation is similarly puzzling); (2) they had a density approaching that of a flatfish; (3) they were secured to the substrate in some manner; (4) they lived partially or wholly bene ath the substrate surface.