The Ediacaran-Cambrian (E-C) transition marks the most important geobiological revolution of the past billion years, including the Earth's first crisis of macroscopic eukaryotic life, and its most spectacular evolutionary diversification. Here, we describe competing models for late Ediacaran extinction, summarize evidence for these models, and outline key questions which will drive research on this interval. We argue that the paleontological data suggest two pulses of extinction - one at the White Sea-Nama transition, which ushers in a recognizably metazoan fauna (the 'Wormworld'), and a second pulse at the E-C boundary itself. We argue that this latest Ediacaran fauna has more in common with the Cambrian than the earlier Ediacaran, and thus may represent the earliest phase of the Cambrian Explosion.
