Archaeocyatha: Fossil Record

The first archaeocyath fossils appear roughly 530 million years ago at the base of the Tommotian stage of the Lower Cambrian. During the subsequent 10 million years, the archaeocyaths were incredibly successful, diversifying into an amazing array of forms and playing a dominant role in the construction of the Earth's first reefs. As fantastic as their diversification was, there demise was just as dramatic. By the end of that 10 million year period, these reef builders had all but disappeared. The last recorded archaeocyath is a single species from the Upper Cambrian of Antarctica. Note that the illustrated number of archaeocyathan families present during the Lower Cambrian is roughly one half of the actual number known (an astonishing 120) due to space limitations.