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Despite 70 years of study, Dickinsonia remains one of the Ediacara biota’s most enigmatic taxa with both morphological characters and phylogenetic affinities still debated. A large population of relatively small Dickinsonia costata present on a semi-contiguous surface from the Crisp Gorge fossil locality in the Flinders Ranges (South Australia) provides an opportunity to investigate this taxon in its juvenile form. This population supports earlier findings that suggest D. costata’s early growth was isometric, based on the relationship between measured variables of length and width. The number of body units increases with length, but at a decreasing rate. A correlation between a previously described physical feature, present as a shrinkage rim partially surrounding some specimens and a novel, raised lip in some specimens, suggests that both features may have been the result of a physical contraction in response to the burial process, rather than due to a gradual loss of mass during early diagenesis. A marked protuberance in 15% of the population is also noted in limited specimens within the South Australian Museum collections and appears to be present only in juvenile D. costata. Both the abundance and narrow size range of this population support the notion that Dickinsonia was a hardy opportunist, capable of rapid establishment and growth on relatively immature textured organic-mat substrates.

Ediacara fossil surfaces from the Flinders Ranges (South Australia) commonly record excellent preservation quality and can provide a palaeoecological window into some of the oldest communities on Earth (ca. 555 Ma). An excavated semi-contiguous sandstone bed of 6.5 m2 from a fossil locality at Crisp Gorge in the central Flinders Ranges records an abundance of taxa and structures characteristic of White Sea assemblage communities. Stratigraphic analysis places the fossil surface within the Oscillation Rippled Sandstone Facies of the Ediacara Member at Crisp Gorge. The community appears to be predominantly juvenile forms, with Dickinsonia costata, Parvancorina minchami and Tribrachidium heraldicum present only within interpreted juvenile size ranges. The textured organic surface contains structures including low relief ridges and round bosses, but overall records a smooth bed surface and is interpreted as representing a surface with only an immature microbial mat developed before burial. No effaced or decayed organisms were identified. Community analysis describes an intermediate Shannon diversity (1.27) and an uneven community dominated by the population of D. costata, which comprises more than 50% of the individuals. The examined parameters, when combined with the presence of small, juvenile taxa and an immature organic mat, suggests that the community inhabiting this surface prior to its catastrophic burial may have been comparable to a modern early-stage, primary successional community. The Crisp Gorge bed emphasizes that Ediacara fossil surfaces from South Australia span a range of developmental stages and offer a window into Ediacaran sea-floor communities at various stages of maturity. Refereed/Peer-reviewed