AN UNLIKELY ECOSYSTEM ENGINEER: EXPLORING THE ROLE OF FUNISIA DOROTHEA AS A CONTROL ON DIVERSITY IN ONE OF EARTH’S EARLIEST COMPLEX ECOSYSTEMS, THE EDIACARA MEMBER, SOUTH AUSTRALIA

The Ediacara Biota represent the first complex, community forming animals on Earth, and while they preserve the advent of many key Metazoan ecologies (e.g., scavenging and mobility), the simple, soft-bodied members of the Ediacara Biota are generally not perceived as important ecosystem engineers. However, the Ediacara Member of South Australia provides evidence for an unique eukaryote-grade Ediacaran ecosystem engineer: Funisia dorothea. Funisia is a modular tubular organism that lived extending up to 30 cm into the water column and is distinct from other fossils of the Ediacara Member in its characteristic abundance and dense packing of individuals. Most commonly, Funisia is preserved in populations of over 1,000 densely packed individuals covering up to 10 m² of fossiliferous surface, making Funisia the most abundant eukaryote-grade fossil in the Ediacara Member by an order of magnitude. With the ability to dominate square meters of seafloor, Funisia was potentially an important control on patterns in diversity, evenness, and preservation.

To interpret the potential impact that Funisia abundance had on preserved patterns in community structure, we present biostratinomic and paleoecological data from seven excavated Funisia-dominated bedding planes from the Ediacara Member, Nilpena Station. Across the Funisia-dominated beds, each of which represent the casting of in situ communities on the base of episodic storm deposits, we observe that Funisia-dominated surfaces characterized by a higher taxonomic diversity also preserve highly degraded Funisia taphomorphs, indicating that the Funisia population had been dead and exposed at the sediment water interface for an ecologically significant period of time during which, other organisms lived on the degraded Funisia. In contrast, Funisia-dominated surfaces that preserve lower levels of taxonomic diversity are biostratinomically consistent with Funisia populations that were buried alive. These repeating patterns in community structure of Funisia-dominated surfaces indicates that Funisia played an unique and dichotomous role as an Ediacaran ecosystem engineer, sequestering resources and restricting benthic recruitment in life but serving as a habitable organic surface that facilitated the establishment of a diverse benthic community in death.