ONTOGENY OF THE EDIACARAN TUBULAR ORGANISM FUNISIA DOROTHEA, NILPENA EDIACARA NATIONAL PARK, SOUTH AUSTRALIA

Funisia dorothea, a tubular organism comprised of modular, serially repeating elements is the most abundant organism, by an order of magnitude, found within the Ediacara Member at Nilpena Ediacara National Park (NENP) in South Australia. The occurrence of Funisia in tightly packed, size-similar populations covering up to ~10 m² has been hypothesized to reflect synchronous aggregate growth via spatfall, representing some of the earliest evidence for sexual reproduction in the fossil record and implying an affinity with Cnidaria or Porifera. Funisia has additionally been inferred to have grown via terminal addition of modules or, more rarely, via branching of tubes. However, the ontogeny of Funisia from the juvenile to adult stage is unknown due to a lack of well-preserved Funisia in smaller size classes. New material from a single bed at NENP preserves Funisia in the small size class (width = ~1 – 3 mm) with well-defined modules that can be compared in size and shape to that of the intermediate (width = 4 – 6 mm) and large (width > 6 mm) size classes. These specimens provide an opportunity to determine whether they grew via module addition and expansion or if the nature of their growth was distinct (e.g., expansion and joining of modules). Other members of the Ediacara Biota (e.g., Dickinsonia), while phylogenetically distinct from Funisia, have been demonstrated to have grown via terminal addition and expansion of modules, providing a point of comparison. Results from this study provide further insight into the disparity, or lack thereof, in ontogenetic strategies in Earth’s earliest complex lifeforms.