Abstract

A new edrioasteroid fauna from the Ordovician of Morocco, North Africa includes eight new isorophid species placed in six genera of which three are new. A phylogenetic analysis of Moroccan genera and other taxa places these new edrioasteroids into a phylogenetic framework. Pyrgocystidae is redefined to include plesiomorphic isorophids with hood plates underlying the cover plates. New pyrgocystid taxa include Streptaster nodosus sp. nov., Belochthus? chauveli sp. nov., Argodiscus espilezorum sp. nov. and Moroccopyrgus matacarros gen. et sp. nov. Isorophinid taxa include Isorophus africanus sp. nov., Isorophusella gutii sp. nov., Euryeschatia reboulorum gen. et sp. nov. and the morphological aberrant Anedriophus moroccoensis gen. et sp. nov. These taxa are attached either epibiotically on conulariids or echinosphaeritid rhombiferans, or encrust large bioclasts such as cephalopods and trilobites in a siliciclastic environment that is otherwise devoid of suitable hard substrates. The presence of close relatives of North American taxa in this Perigondwanan section indicates a high degree of communication between North America and North Africa in Ordovician time. Also described are two species of an unusual eocrinoid? Hexedriocystis gen. nov., the type species H. inexpectatus sp. nov. and H. mimus sp. nov., that is a close mimic of isorophid taxa.