The external morphology and its variability, myocardinal apparatus, and shell structure of both valves of the radiolitid rudist Eoradiolites plicatus (Conrad) are described, based on the examination of about one hundred well-preserved, fairly complete specimens that are free of sediment matrix, found in a single bed of an ammonite-bearing Albian succession ('Knemiceras beds', Zebbag Formation) in central Tunisia. This study provides the most nearly complete knowledge of any Eoradiolites species to date. With this background, all previous records of E. plicatus, as well as the taxonomic status of the other Albian species of the genus, are revised considering both original material, when available, and published papers. As a result, the systematics of Eoradiolites is simplified. © 2010 The Paleontological Society.