. "Celmus is an extinct genus from a well known class of fossil marine arthropods, the trilobites. It lived during the later part of the Arenig stage of the Ordovician Period, approximately 471 to 478 million years ago."@en . "Celmus is an extinct genus from a well known class of fossil marine arthropods, the trilobites. It lived during the later part of the Arenig stage of the Ordovician Period, approximately 471 to 478 million years ago."@en . "Celmus"@en . "Animalia"@en . . . "Australopyge"@en . . . "Arthropoda"@en . . "Late Arenig"@en . .