Carcassonne, France
Carcassonne, France

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Martin E.L.O.,University Claude Bernard Lyon 1 | Vidal M.,CNRS Oceanic Domains Laboratory | Vizcaino D.,rue Jean Baptiste Chardin | Vaucher R.,University Claude Bernard Lyon 1 | And 2 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2016

Trilobites are a major component of both biomineralized and soft-bodied assemblages of the Fezouata Biota, central Anti-Atlas, Morocco. Trilobite taxa of the Fezouata Shale (Tremadocian–Floian) in the Zagora area are typical of Lower Ordovician communities from shallow shelf environments, and show strong affinities with Early Ordovician assemblages from the Montagne Noire (southern France). Dramatic variations in both taxonomic composition and taphonomic attributes, together with the sedimentological facies changes, allow us to discriminate the palaeoenvironmental versus stratigraphic control on trilobite assemblages. Three communities are described along an onshore–offshore profile, namely the pilekiid-bavarillid, Agerina and raphiophorid biofacies. Additionally, three stratigraphic assemblages are identified: assemblage 1 is confined to the late Tremadocian, assemblage 2 ranges from late Tremadocian to middle Floian and assemblage 3 is restricted to the Floian. The higher diversity of some levels is explained by storm-induced inputs of debris from taxa living in adjacent environments. Additionally, control of relative seal level variation on some peculiarities of the trilobite fauna (specific endemicity, lack of some expected taxa) is evidenced in the Fezouata Shale. Finally, temporary dysoxic events are highlighted by preliminary geochemical analyses, probably allowing episodic exceptional preservation. © 2016 Elsevier B.V.


Devaere L.,Lille University of Science and Technology | Clausen S.,Lille University of Science and Technology | Monceret E.,rue des Pins | Vizcaino D.,rue Jean Baptiste Chardin | And 2 more authors.
Palaeontology | Year: 2014

A carbonate bed of the Pardailhan Formation, early Cambrian, southern Montagne Noire (southern France), provided microfossils such as Hyolithellus sp., Torellella cf. mutila and Torellella sp. along with numerous disarticulated pieces of composite skeletons such as valves of the brachiopod Eoobolus priscus and of the bradoriid Monceretia erisylvia, and chancelloriid sclerites (Chancelloria sp.). The assemblage also furnished a rich set of sclerites from the tommotiid Kelanella altaica. Five morphological variations of the latter have been identified. The presence of concentric ribs formed by distal inflation of selected shell laminae in Kelanella supports its assignment to the camenellans. More particularly, the presence of transverse structures within the internal cavity (septa) of Kelanella suggests a close relationship with the Lapworthellidae. However, the latter differ from Kelanella by the continuous morphological variation along their scleritome which is also composed of simple conical elements with uniform ornamentation. Several forms of Kelanella are similar to mitral and sellate sclerites of Camenella, whereas some other forms are comparable to Kennardia. The new material suggests that Kelanella occupies a transitional position between Lapworthellidae and the grouping of Tommotiidae and Kennardiidae. Such a phylogenetic position also implies that the number of sclerite morphotypes tends to decrease within the camenellan scleritome during evolution. © The Palaeontological Association.

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