PeriodonPeriodon is a genus of conodonts which existed in what is now Canada, Iran, Argentina, China, Russia, and the United States during the Ordovician Period. It was described by Hadding in 1913, and the type species is P. aculeatus.SpeciesPeriodon flabellum Lindström, 1954Periodon zgierzensis Dzik, 1976Periodon aculeatus Hadding, 1913Periodon selenopsis Serpagli, 1974Periodon macrodentatus Periodon hankensis Svend Stouge, 2012