Nicole Grambast-Fessard

Microfaunes, microflores etpaléoenvironnements successifs dans la formation d'El Mers (Bathonien-?Callovien) du synclinal de Skoura (Moyen-Atlas, Maroc)

In the Middle-Atlas (Morocco), the lower part of the “Red beds” (El Mers Formation), Middle Jurassic in age,contains various microfossils which permit to reconstruct the palaeoenvironmental evolution of this area for this period. Populations of abundant charophytes, collected at the base of the formation, are assigned to a new species: Porochara hians Feist & Grambast-Fessard. Species of ostracods are generally different than the European synchronous ones. The first ostracods appearing at the base of the formation are monospecific and euryhaline (continental or brackish). They are more diversified above and correspond to a typical marine depositional environment. Marine incursions occur up to the top of the formation where they are represented by limestones bearing dasycladales and benthonic foraminifera, Late Bathonian to Early Callovian in age. The transgressive trend observed at the top of the “El Mers Formation” can be correlated to the deepening-upward trend of the Transgressive Systems Tract from the Depositional Sequence DS 158,5 (3rd order eustatic cycle LZA 3-1) which corresponds to a general transgression of the sea over the palaeostructures of the Jurassic Tethyan Basin.

Ancient Dasycladales and Charophyta: convergences and differences, with special attention to Munieria baconica

Abstract We present a new morphological study of the Cretaceous species Munieria baconica, combined with a critical analysis of charophyte thalli, with the aim of determining the systematic attribution of the genus Munieria, either to the Dasycladales or to the Charophyta. Our study shows that thalli of M. baconica are organized as in the Dasycladales: they possess a central stem, on which arise whorls of primary branches (radial canals), each bearing at their distal end a cluster of secondary branches with calcified internal partitions resembling rose windows. There appears to have been cytoplasmic continuity between the different organs composing the thallus, as in Dasycladales. Charophyte thalli, however, are multicellular; the central canal never ramifies internally, and spine-cells forming structures like rose windows arise from cortical cells. The thalli of the clavatoracean charophyte Septorella ultima, which has been designated as a Munieria species by several authors, differ totally from those of Munieria. Emended diagnoses of the genus Munieria and of its type species M. baconica are given. From a palaeoecological point of view, the co-occurrence of M. baconica and Atopochara trivolvis (Clavatoraceae) in the type locality of M. baconica in the Bakony Mountains (Hungary) confirms that fossil dasyclads can inhabit brackish environments, as do, for example, recent Batophora species.

Deux nouveaux représentants du genre Ascidiella(Clavatoraceae, Charophyta)

Resume Description de deux nouvelles especes du genre Ascidiella Grambast : A. inflata et A. irregularis, du Cretace inferieur de la peninsule iberique.