Excursion dans le Néoprotérozoïque supérieur et le Cambro-Ordovicien de l'Anti-Atlas central

International audienc

Digitization of fossils from the Fezouata Biota (Lower Ordovician, Morocco): Evaluating computed tomography and photogrammetry in collections enhancement

International audience(K. El Hariri), [email protected] (A. El Albani), [email protected] (A. Azizi), [email protected] (A. Mazurier), [email protected] (B. Lefebvre). Abstract Palaeontological collections housing material from the Fezouata Shale Lagerstätte (Lower Ordovician, Morocco) are of a high scientific interest as they testify to the existence of Burgess Shale-type taxa in one of the most critical Palaeozoic period: the Cambrian-Ordovician transition. The preservation of this unique patrimony can benefit from the emergence of imaging methodologies that have provided innovative ways in three-dimensional (3D) digitization. Computed tomography and photogrammetry were applied in order to create 3D models of fossils from the Fezouata Biota. Tomographic results show the exciting potential of these techniques in internal investigation of fossils, while photogrammetric method enables surface reconstructions with great accuracy in terms of texture, color and morphology, and can be convenient when internal exploration is not required. Three-dimensional digitization techniques thus seem to be reliable methods suited to highlight the potential of palaeontological data housed in museums and make easier the scientific dissemination of information

Les Fezouata : le Burgess Shale ordovicien du Maroc

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The Lower Ordovician Fezouata Lagerstätte, Central Anti-Atlas, Morocco (Feb. 14-16, 2018). IGCP 653 regional workshop & field excursion

guide d'excursion géologique lié à la réunion régionale du PICG 653 à Marrakech (Maroc) en février 201

Exceptionally preserved soft parts in fossils from the Lower Ordovician of Morocco clarify stylophoran affinities within basal deuterostomes.

10 pagesInternational audienceThe extinct echinoderm clade Stylophora consists of some of the strangest known deuterostomes. Stylophorans are known from complete, fully articulated skeletal remains from the middle Cambrian to the Pennsylvanian, but remain difficult to interpret. Their bizarre morphology, with a single appendage extending from a main body, has spawned vigorous debate over the phylogenetic significance of stylophorans, which were long considered modified but bona fide echinoderms with a feeding appendage. More recent interpretation of this appendage as a posterior “tail-like” structure has literally turned the animal back to front, leading to consideration of stylophorans as ancestral chordates, or as hemichordate-like, early echinoderms. Until now, the data feeding the debate have been restricted to evaluations of skeletal anatomy. Here, we apply novel elemental mapping technologies to describe, for the first time, soft tissue traces in stylophorans in conjunction with skeletal molds. The single stylophoran appendage contains a longitudinal canal with perpendicular, elongate extensions projecting beyond hinged biserial plates. This pattern of soft tissues compares most favorably with the hydrocoel, including a water vascular canal and tube feet found in all typical echinoderms. Presence of both calcite stereom and now, an apparent water vascular system, supports echinoderm and not hemichordate-like affinities

Taphonomic pathway of exceptionally preserved fossils in the Lower Ordovician of Morocco

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Palaeoecological aspects of the diversification of echinoderms in the lower Ordovician of Central Anti-Atlas, Morocco

Echinoderms are one of the major components of benthic faunas in the Lower Ordovician sequence near Zagora, central Anti-Atlas, Morocco. The Fezouata Shale (Tremadocian–late Floian) has yielded numerous, exquisitely preserved echinoderm assemblages, ranging through several stratigraphic levels and palaeoenvironmental conditions. These associations offer a unique opportunity to document both evolutionary and palaeoecological aspects of echinoderm diversification in high-latitude, siliciclastic-dominated western Gondwana sediments, where rapid in situ burials facilitated excellent faunal census conditions. Lower shoreface deposits of the Fezouata Shale provide the most complete record of successive echinoderm faunas. In late Tremadocian times, these relatively shallow shelf deposits show the progressive replacement of low-diversity, opportunistic, Cambrian-like, dwarfed communities dominated by cornute stylophorans, in unhospitable, dysoxic environmental conditions by higher diversity benthic assemblages, more typical of the Great Ordovician Biodiversification Event and dominated by blastozoans, on well-oxygenated sea-floors. The turnover of the Ordovician radiation was apparently slightly delayed in more proximal settings. Eocrinoid meadows persisted in shallower environmental conditions up to the middle Floian. In the late Floian, they were replaced by diploporite-dominated communities, typical of later Ordovician high-latitude peri-Gondwanan faunas. From a palaeobiogeographic point of view, low-diversity assemblages display relatively strong affinities with cosmopolitan late Cambrian echinoderm faunas, whereas high-diversity communities are dominated by peri-Gondwanan taxa