The Avalon explosion (named from the Precambrian fauna of the Avalon Peninsula) is a proposed evolutionary event in the history of the Metazoa. It is the equivalent of the Cambrian explosion for the current phyla. The Avalon explosion happened about 33 million years earlier than the Cambrian explosion (about 575 million years ago).
Trace fossils of these Avalon organisms have been found worldwide, and represent the earliest known complex multicellular organisms. The Avalon explosion is also called the Ediacara biota radiated event. The biota largely disappeared contemporaneously with the rapid increase in biodiversity known as the Cambrian explosion.
The Avalon explosion was proposed by Virginia Tech paleontologists through the analysis of the morphological space change in several Ediacaran assemblages. The discovery suggests that in the early evolution of animals, there may have been more than one explosive event. The original analysis has been the subject of dispute in the literature.
The Avalon explosion appears similar to the Cambrian explosion in the rapid increase in diversity of morphologies in a relatively small time frame, followed by diversification within the established body plans, a pattern similar to that observed in other evolutionary events.