Ordovician echinoderms
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Exceptionally preserved fossils yield crucial information about the evolution of Life on Earth. The Fezouata Biota from the Lower Ordovician of Morocco is a Konservat-Lagerstätte of major importance, and it is today considered as an... more
Exceptionally preserved fossils yield crucial information about the evolution of Life on Earth. The Fezouata Biota from the Lower Ordovician of Morocco is a Konservat-Lagerstätte of major importance, and it is today considered as an 'Ordovician Burgess Shale.' This biota was discovered only some 15 years ago, but geological studies of the area date back to the beginning of the 20th century. Pioneering geological investigations lead to the discovery of Ordovician strata in the Anti-Atlas (1929) and ultimately resulted in their formal subdivision into four main strat-igraphic units (1942). In the Agdz area, the presence of fossiliferous Tremadocian (Lower Ordovician) strata was suspected as early as 1939, but only definitively confirmed in 1955. In the 1960s–1990s, Jacques Destombes provided the first detailed biostratigraphic framework for the Lower Ordovician of the Anti-Atlas, and collected thousands of fossils that were subsequently described in a series of monographs. In the early 2000s, exceptionally preserved fossils were discovered in the Fezouata Shale (Tremadocian–late Floian) in the central Anti-Atlas by Mohamed 'Ou Saïd' Ben Moula. This biota, now known as the Fezouata Biota, is of utmost importance, for it demonstrates the extent in the fossil record of non-biomineralising animals typical of the 'Cambrian Explosion' into the Ordovician, during the 'Great Ordovician Biodiversification.' Although most components are still in need of formal descriptions, a fairly good picture of the composition and organisation of this biota, and how it contributes to our understanding of the early evolution of metazoan communities, can now be depicted. Moreover, recent studies have substantially clarified the biostratigraphical and palaeoenvironmental context of the Fezouata Shale, and are now being followed up by detailed investigations of the taphonomy, geochemistry and micropalaeontology of this unique Konservat-Lagerstätte. These efforts will soon greatly benefit from the recovery of fresh, unweathered samples from drill cores.
The site of Bou Nemrou, in the Western Tafilalt (eastern Anti-Atlas, Morocco) is one of the very few Konservat-Lagerstätten known so far in the world to have yielded numerous remains of Late Ordovician softbodied fossils associated with... more
The site of Bou Nemrou, in the Western Tafilalt (eastern Anti-Atlas, Morocco) is one
of the very few Konservat-Lagerstätten known so far in the world to have yielded
numerous remains of Late Ordovician softbodied fossils associated with an abundant and diverse marine benthic fauna. This locality has also yielded several levels (starfish beds) extremely rich in exquisitely preserved echinoderms. Their remarkable preservation possibly results from the rapid, in situ burial of large, particularly dense, living communities (echinoderm meadows) by storm deposits. The Bou Nemrou starfish beds are dominated by eocrinoids and stylophorans, associated with crinoids, cyclocystoids, edrioasteroids, and ophiuroids. This composition is typical of the cool assemblages of the Mediterranean Province. The Bou Nemrou starfish beds may result from the opportunistic colonisation of the sea-floor by dense populations of echinoderms, during short phases of environmental disturbance.
of the very few Konservat-Lagerstätten known so far in the world to have yielded
numerous remains of Late Ordovician softbodied fossils associated with an abundant and diverse marine benthic fauna. This locality has also yielded several levels (starfish beds) extremely rich in exquisitely preserved echinoderms. Their remarkable preservation possibly results from the rapid, in situ burial of large, particularly dense, living communities (echinoderm meadows) by storm deposits. The Bou Nemrou starfish beds are dominated by eocrinoids and stylophorans, associated with crinoids, cyclocystoids, edrioasteroids, and ophiuroids. This composition is typical of the cool assemblages of the Mediterranean Province. The Bou Nemrou starfish beds may result from the opportunistic colonisation of the sea-floor by dense populations of echinoderms, during short phases of environmental disturbance.
Four distinct echinoderm Lagerstätten have recently been discovered in the Upper Ordovician of the eastern Anti-Atlas, Morocco. They have yielded hundreds of exquisitely preserved specimens. Their taphonomy and associated lithology both... more
Four distinct echinoderm Lagerstätten have recently been discovered in the Upper Ordovician of the eastern Anti-Atlas, Morocco. They have yielded hundreds of exquisitely preserved specimens. Their taphonomy and associated lithology both suggest rapid, in situ burial. Here we discuss the diverse range of assemblages represented and their significance to the diversity of echinoderms in the Lower Palaeozoic. The oldest assemblage (Izegguirene Formation, lowermost Caradoc) is dominated by eocrinoids, large ophi-uroids, and mitrate stylophorans associated with rare crinoids. It shows strong similarities with slightly older faunas described from the underlying Ouine-Inirne Formation (Llandeilian) in the Central Anti-Atlas. The second assemblage (lower part of the Lower Ktaoua Formation, lower-middle Caradoc) is composed of eocrinoids (Cardiocystites) and small ophiuroids (encrinasterid indet.). The third assemblage was collected in the upper part of the Lower Ktaoua Formation (lowermost Ashgill). This 'starfish' bed is dominated by ophiuroids and large solutes, associated with common diploporites and rhombiferans, and rare crinoids and mitrates. Finally, the youngest assemblage (lower part of Upper Tiouririne Formation, lower Ashgill) has yielded abundant remains of edrioasteroids and rhombiferans.
Plusieurs Lagerstätten à échinodermes ont été découverts au cours des dix dernières années dans l'Ordovicien supérieur de l'Anti-Atlas oriental (Tafilalt occidental, Maroc). Ces niveaux ont livré des assemblages particulièrement riches et... more
Plusieurs Lagerstätten à échinodermes ont été découverts au cours des dix dernières années dans l'Ordovicien supérieur de l'Anti-Atlas oriental (Tafilalt occidental, Maroc). Ces niveaux ont livré des assemblages particulièrement riches et diversifiés d'échinodermes. La préservation exceptionnelle de ces organismes témoigne d'un enfouissement rapide et in situ de communautés benthiques particulièrement denses constituées quasi-exclusivement d'échinodermes. Trois assemblages sont décrits : Bou Nemrou (Sandbien basal), piste de Jorf (Sandbien supérieur) et enfin, Tizi n'Mouri (Katien supérieur). L'intérêt scientifique majeur de ces faunes (implications paléoécologiques et paléogéographiques) est brièvement présenté. Enfin, la préservation de ces gisements, qui constituent un élément majeur du patrimoine paléontologique du Sud marocain, est abordée. Late Ordovician echinoderm Lagerstätten from the eastern Anti-Atlas (Morocco): an example of exceptional scientific heritage worthy of protection. Abstract. In the last ten years, several Late Ordovician echinoderm Lagerstätten have been discovered in the eastern Anti-Atlas (western Tafilalt) of Morocco. These levels have yielded extremely rich and diverse echinoderm assemblages. The exquisite preservation of most organisms suggests rapid and in-situ burial of large, particularly dense benthic communities largely dominated by echinoderms. Three « starfish beds » are briefly described: Bou Nemrou (earliest Sandbian), piste de Jorf (late Sandbian), and Tizi n'Mouri (late Katian). The major scientific relevance of these faunas is outlined herein (for example their palaeoecological and palaeogeographical implications). Finally, the conservation of these levels, which represent a major piece of the palaeontological heritage of southern Morocco, is discussed.
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