CLAPHAM, M.E.*; NARBONNE, G.M.; GEHLING, J.G.: Community ecology of Ediacaran fossil assemblages at Mistaken Point, Newfoundland

Ediacaran fossils at Mistaken Point have been reliably dated at 565 Ma, making them the oldest complex animals in the world. The biota includes the most spectacularly preserved Neoproterozoic fossil assemblages in the world and is one of the few deep-water occurrences of these organisms. Soft-bodied organisms are preserved as in situ census populations on large bedding surfaces, allowing ecological tests normally applied to modern communities to be performed on the fossil assemblages. These tests, such as measures of diversity and spatial pattern, yield valuable information about the earliest complex metazoans and their ecosystem. In addition, the presence of dozens of bedding surfaces spanning a two kilometre stratigraphic interval provides a superb dataset for analysis of long-term changes in community structure and comparison with modern slope communities. Species composition, diversity and spatial patterns were measured for seven of the most diversely fossiliferous surfaces. Although nineteen fossil types are present in total, species composition varies considerably between surfaces and several forms are restricted to a single bedding plane. No taxon occurs on all surfaces. Shannon diversity coefficients are also highly variable and range from 0.18 to 1.40. None of the community parameters examined seems to show any consistent trend from the oldest to youngest surfaces. Single-species spatial distributions are roughly divided between aggregated and random patterns; regular patterns are rare. In contrast, multi-species spatial patterns are dominantly random and only three pairwise interactions showed association or segregation. In general, Ediacaran community attributes, especially abundance and diversity, are remarkably similar to modern communities.