Abstract The extensive, predominantly siliciclastic deposits of the Upper Ordovician of the Tafilalt have long been the subject of scientific investigation. In the past 25 years, intensified collecting for commercial purposes has resulted in the discovery of several exceptionally-preserved faunas (Konservat-Lagerstätten) in the Tafilalt region, preserving a range of non-biomineralized and soft-bodied organisms. The preservation of these fossils in the coarse clastic sediments of the Tafilalt is surprising, and in the case of soft-bodied organisms, remarkably similar to the preservational mode of typical Ediacaran biotas. These relatively recent discoveries have increased the scientific significance of the Tafilalt Biota, providing an unparalleled insight into the composition and temporal evolution of the shallow, open-marine ecosystems and their denizens during the later stages of the Great Ordovician Biodiversification Event. At least nine different phyla, in addition to several soft-bodied problematica are represented in the Tafilalt. While the highly diverse and remarkably well-preserved echinoderm and euarthropod faunas are most emblematic for the Tafilalt Biota, further studies have revealed a relatively high diversity of molluscs and brachiopods. Among soft-bodied fossils, the problematic paropsonemid eldonids are iconic for the Tafilalt and stand out both through their abundance, and their wide temporal and geographical range throughout the area.

Abstract Anomalocystitid mitrates represent one of the most diverse and long ranging clade of stylophorans (Early Ordovician–Middle Devonian). Although they probably originated from a peri-Gondwanan stock of early mitrocystitids during the Floian, the fossil record of anomalocystitids in the Middle–Upper Ordovician of the Mediterranean Province remains extremely scarce and largely underestimated. The unusually shaped anomalocystitid genus Diamphidiocystis was originally described in the latest Katian–Hirnantian of North America (Illinois). However, earlier occurrences of this genus in the late Darriwilian of western France (Brittany) suggest a probable peri-Gondwanan origin. Based on new Middle to Late Ordovician material from the Anti-Atlas (Morocco), Bohemia (Czech Republic) and Brittany (France), all occurrences of Mediterranean Diamphidiocystis are considered as conspecific and formally described as D. regnaulti sp. nov. The palaeobiogeographical significance of Ordovician anomalocystitid mitrates is discussed.

Abstract Cornute stylophorans are a minor, although typical, component of Middle–Late Ordovician echinoderm assemblages adapted to soft siliciclastic substrates in high-latitude peri-Gondwanan regions. All previously reported occurrences of Darriwilian–Katian cornutes from the Czech Republic, France, Morocco and Spain are revised and their plate homologies reassessed. The genera Beryllia and Juliaecarpus are reinterpreted as junior synonyms of Domfrontia , and Thoralicystis is synonymized with Bohemiaecystis . Several Mediterranean scotiaecystids previously assigned to Bohemiaecystis and/or Scotiaecystis are placed within Thoralicarpus gen. nov., and cornute taxa originally left in open nomenclature by Chauvel are formally described as Bohemiaecystis chouberti sp. nov. (AVI) and Destombesicarpus izegguirenensis gen. et sp. nov. (AVIII). Other new Mediterranean taxa include Arauricystis clariondi sp. nov., Destombesicarpus budili gen. et sp. nov., Milonicystis reboulorum sp. nov., Thoralicarpus bounemrouensis gen. et sp. nov., and T . prokopi gen. et sp. nov. The six cornute genera identified in Darriwilian–Katian Moroccan echinoderm Lagerstätten are also present in coeval assemblages of at least one other Mediterranean region, thus supporting the existence of strong faunal affinities between the Anti-Atlas, the Armorican Massif, the Barrandian area and the Iberian Peninsula.

Abstract In the western Tafilalt area, eastern Anti-Atlas (Morocco), solutan echinoderms are a major faunal element of most echinoderm Lagerstätten occurring within the Lower Ktaoua Formation (late Sandbian–early Katian). For the first time, members of the class Soluta are formally described from Morocco and Africa. All solutans from the Lower Ktaoua Formation are identified as Dendrocystites aff. sedgwicki . Three size-related morphotypes, probably corresponding to successive growth stages (‘juvenile’, ‘adult’ and ‘gerontic’), could be distinguished within the abundant and well-preserved material from Morocco. The occurrence of the genus Dendrocystites in the western Tafilalt confirms the strong faunal affinities between Morocco and other regions of the Mediterranean Province (Czech Republic and Spain) in Late Ordovician times. In high palaeolatitude (peri-)Gondwanan areas, Dendrocystites was a gregarious solutan living in shallow, siliciclastic settings at or above the storm-wave base.