CASTLEMAINIAN STAGE

time division of the Ordovician Period in Australia and New Zealand (the Ordovician Period began about 500,000,000 years ago and lasted about 70,000,000 years). The Castlemainian Stage precedes the Yapeenian Stage and follows the Chewtonian Stage. Several graptolite fossil zones, shorter divisions of time within the stage, are recognized in the Castlemainian and are based on various subspecies of Isograptus caduceus. Castlemainian faunas show affinities with North American and European faunas.