Abstract This monographic study deals with a major marine faunal turnover during the Late Ordovician global greenhouse/icehouse episodes. The Late Ordovician was marked by one of the two greatest global sea-level rises and inundations of the North American paleocontinent during the Phanerozoic (last 544 million years), accompanied by a rapid diversification of invertebrate faunas in shallow, tropical, epicontinental seas. Toward the end of the Late Ordovician, continental glaciation in the southern hemisphere (Gondwana landmass) caused a major sea-level drop and marine regression from North America, bringing about the first of the five major mass extinction events in life history. Anticosti Island was part of the larger Anticosti basin, located on the eastern continental shelf of the North America paleocontinent, and was covered by a shallow, tropical sea in the Late Ordovician epoch. During the latest Ordovician global mass extinction event, the marine shelly benthos (bottom) of the Anticosti basin experienced a significant local radiation. This provides a great opportunity for us to investigate the response of marine life to a major environmental crisis. This monographic study aims to document the diversity change of brachiopods (one of the major groups of marine life during the Ordovician Period) from pre-extinction to extinction times.