Origination and Extinction Rates in the Oldest Communities: Biostratigraphic Challenges to Subdividing the Ediacaran Period

Establishing a robust biostratigraphic framework for the Ediacaran Period has proven difficult. Prior to the emergence of mineralized skeletons in the latest Ediacaran, preservation is highly selective, and taphonomic processes can obscure true first and last appearances of potential index fossils. Compounding this problem, uncertainty surrounding the classification and biology of many Ediacaran taxa complicates efforts to resolve time- and space-dependent patterns, especially in global, inter-basin correlations. Despite these issues, recent work has identified important patterns in how the earliest Ediacaran communities assembled; however, regional variation in early Ediacaran biodiversity remains poorly understood, despite its integral role in linking local- and bed-scale distributions to global-scale patterns. Here, we compiled bed-level genus occurrence data and radiometric dates from the Bonavista and Mistaken Point basins in Newfoundland, Canada, to compare how ecological and evolutionary patterns varied over time and between contemporaneous basins. To quantify and compare these patterns, we calculated per capita rates of origination and extinction, taxonomic diversity, and functional diversity. We find few synchronous peaks or shifts in diversity or evolution between basins: both taxonomic and functional diversity shift in different ways, and at different times between basins. We also find differences in peaks origination and extinction between basins in both magnitude and timing. As such, despite representing some of the best-studied sections in the world with the most abundant Ediacaran fossiliferous beds constrained by multiple high-precision radiometric dates across several local basins, deciphering regional versus global signals remains a challenge and must be accounted for when trying to resolve global-scale processes from data heavily shaped by a few, albeit well-sampled, localities.