"Ktaoua Formation" In the central Moroccoan Anti-Atlas, the Ktaoua Formation (Late Ordovician) consists of clayey sediments and sandstone bands. In this image I show a Selenopeltis trilobite, orthoceratids, crinoids, Eldonia, aglaspidids, brachiopods and the marrellid Furca (right). Media: Adobe Photoshop. Click on arrows to get closer or view next illustration.