An iconic member of the Ediacara Biota, Dickinsonia Sprigg is one of few such taxa with multiple species. Here we use gaussian finite mixture models to assess the validity of species distinctions for this genus. Our results indicate that the five described species of Dickinsonia from the Ediacara Member, South Australia are better classified as two based on multiple approaches. Two different methods for dimension reduction both provide strong support for two groups, with overlapping but distinct mixture models. The variable selection method produces the most biologically realistic clusters, indicating that the two species can be primarily differentiated based on the greater relative size of the anteriormost unit of Dickinsonia costata Sprigg compared with Dickinsonia tenuis Glaessner & Wade. Despite differences in aspect ratio and number of modules, both species regulated growth to maintain overall shape. The greater likelihood of preservation of a midline and an irregular outer margin in D. tenuis highlights differential structural integrity and flexibility. Co-occurrence in the Ediacara Member indicates that both species occupied the same environments and temporal distribution. Smaller maximum and average size, combined with higher abundance of D. costata, may suggest a comparatively shorter lifespan and increased rates of reproduction.

The Supplementary Data and associated ReadMe files were created in Excel. Code used for mixture model analysis was written and conducted using R. See main text for further details. 

This dataset consists of measurements obtained from digital photographs. See the main text for more details.