The paucity of temporally-resolved localities with diverse Ediacaran assemblages, combined with difficulties associated with differences in taphonomic regimes before, during, and after the transition hinders this evaluation. We explore temporal and biogeographic distributions of Ediacaran taxa combined with evaluations of functional guild ranges throughout the Ediacaran. To evaluate these proposed explanations for the biotic changes observed at the Ediacaran–Cambrian transition, environmental drivers leading to global mass extinction are compared to biological factors such as predation and ecosystem engineering.

Three alternative hypotheses have been advanced to explain this dramatic change at, or near, the Ediacaran–Cambrian boundary: 1) mass extinction of most Ediacaran forms 2) biotic replacement, with early Cambrian organisms eliminating Ediacaran forms and 3) a Cheshire Cat model, with Ediacaran forms gradually disappearing from the fossil record (but not necessarily going extinct) as a result of the elimination of unique preservational settings, primarily microbial matgrounds, that dominated the Ediacaran. Although metazoans are present in the Ediacaran, their ecological contribution is dwarfed by Ediacaran-type clades of uncertain phylogenetic affinities, while Ediacaran-type morphologies are virtually non-existent in younger assemblages. The Ediacara biota (consisting of various metazoan stem lineages in addition to extinct eukaryotic clades) disappears, and is replaced by more familiar Cambrian and Paleozoic metazoan groups. The Ediacaran–Cambrian transition signals a drastic change in both diversity and ecosystem construction.

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