Dickinsonia from Ediacara: A new look at morphology and body construction

During groundbreaking fieldwork on the taphonomy and sedimentology of the famous fossil deposits at the Ediacara sheep station [Goldring, R., Currnow, C.N., 1967. The stratigraphy and facies of the Late Precambrian at Ediacara, South Australia. Journal of the Geological Society of Australia 14, 195–214.], Roland Goldring formed one of the few collections of original Ediacara fossil materials that can still be accessed outside of Australia. This material, collected from the type locality at Ediacara, is now housed in the Natural History Museum at Oxford, and includes excellent specimens of the enigmatic fossil Dickinsonia costata [Sprigg, R.C., 1949. Early Cambrian ‘jellyfishes’ of Ediacara, South Australia, and Mount John, Kimberly District, Western Australia. Transactions of the Royal Society of South Australia 73, 72–99.]. This first detailed description of the Oxford Dickinsonia material, and its associated wrinkle structures, is discussed with relevance to some wider problems facing Ediacaran taxonomy. Serial photographic reconstruction techniques are used to produce high resolution analyses of these fossils. Attention is drawn to features such as relief inversion of the upper surface, in which a ‘spatulate B segment’ is typically preserved in positive hyporelief while the rest of the fossil is mainly preserved in negative hyporelief. Segments can also appear to bifurcate and merge—a feature which, together with the glide plane of symmetry, is inconsistent with the bilaterian model often argued for this taxon. Controversial and conflicting claims for the presence of circular muscles, a rigid outer cuticle, an axial gut and even radial tentacles can all be explained by a single hypothesis that involves a simple, possibly coelenterate-grade, organism which had a distinctive, hydraulic body structure that underwent stretching, strain, collapse and contraction as the internal turgor pressure in the segments changed, especially during death and burial.