Middle Pennsylvanian, late Atokan-early Desmoinesian echinoderms from an intermontane basin, the Central Colorado Trough

Abstract

Middle Pennsylvanian, Atokan and Desmoinesian, crinoids and echinoids are described from the Belden and Minturn Formations of the Central Colorado Trough. The echinoderms from the Minturn Formation were living in an active intermontane trough setting. They are found in two environments, on the flanks of phylloid algal reefs and in patches on abandoned delta lobes on the gently sloping substrate. Faunas are dominated by cromyocrinids and are similar to stable platform Terrigineous Facies Belt faunas of the Midcontinent.New species described areDicromyocrinus beldenensis, Neoprotencrinus rockensis, andSciadiocrinus wipsorum. Goleocrinus, and the columnal generaBlothronagma, Cyclocaudex, andPlatyplateiumare reported for the first time from the Minturn Formation. The columnal taxaBlothronagma cinctutumandFloricyclus angustimargoare believed to be cromyocrinids.B. cinctutummay be synonomous withSynarmocrinus molasensis, andFloricyclus angustimargomay be synonymous withUlocrinus rockymontanus.