Radiation of the Earliest Calcareous Brachiopods

The Cambrian radiation, and morphological variation, of five calcareous-shelled brachiopod orders, including taxa assigned to both articulates and inarticulates in the past, is reviewed, and analysed cladistically. The oldest known calcareous-shelled brachiopods are early Atdabanian obolellids. Chileides arose in the Botomian, and kutorginids in the Late Atdabanian or early Botomian. The oldest protorthoids [‘articulates’] appear in the middle Early Cambrian, but the group did not radiate until Middle Cambrian times.