Extinction of the Archaeocyatha

Abstract
Archaeocyaths are a group of calcified sponges almost limited to the Early Cambrian. They have undergone a rapid radiation followed by an abrupt decline even more rapid and a total extinction. Rate of this extinction is documented at the generic level and a pattern of extinction is proposed. Changes in palaeotectonics, with the consequent modifications in the environment, and a probable cooling of the climate, are the possible causes of their demise. This extinction involves the disappearance of the first reefs in which Metazoans were, at least partly, implicated.