And now for something completely random: spatial distribution of Dickinsonia on the Ediacaran seafloor

The oldest evidence of motile complex benthic multicellular organisms is found in Ediacaran aged rocks. At Nilpena Ediacara National Park (NENP), South Australia, one of the most iconic of such organisms, Dickinsonia, are found in abundance, with over 500 individuals preserved across the site's 33 in situ, fossiliferous beds. These beds vary in mat type and maturity, community diversity and population size. Here, we investigate six beds using spatial point pattern analysis (SPPA) to compare Dickinsonia spatial distributions between populations. Five populations were best-fit to a completely spatially random pattern, with a single outlier (TC-MM3) exhibiting signs of environmental heterogeneity. When distributions were examined in relation to other taxa, no indication of spatial competition was detected. Univariate and bivariate spatial distributions imply that Dickinsonia was generally not impacted by competition with other taxa, meter-scale environmental heterogeneity, or other external factors. These patterns hold when analyses were split between populations of large and small individuals, and these two size cohorts had no measurable effect on each other's spatial distributions. Additionally, we find no indication of intraspecific competition for Dickinsonia or any change in the preferred resources or habitats with growth. These results suggest that the anactualistic environmental conditions produced by ubiquitous organic mats present across Ediacaran seafloors at NENP provided such abundant nutrients that Dickinsonia did not have to compete for resources at the meter scale. These results further inform community-scale dynamics of Earth's earliest complex ecosystem.