Monique Feist

New insights into Paleozoic charophyte morphology and phylogeny

Examination of Paleozoic charophyte fructifications using microscopy and high-resolution x-ray synchrotron microtomography has revealed that most of them have a utricle that forms a supplementary calcified cover around the gyrogonite. All Paleozoic families with utricles have been assigned to the Sycidiales. We consider the Moellerinaceae to occupy a central position in the phylogeny of the Charophyta. From these, one group of descendants constitutes the gyrogonites inside the utricles of the Sycidiales; a second descendant goup is thought to be the utricle-free ancestors of the Charales prior to inversion of spiralization and reduction in cell number. The Sycidiales have a multilayered wall and an internal vesicle, but their families are distinguished by diversity in orientation of external cells, complexity of the utricle wall, and in presence or absence of antheridia. The solidly packed structure of the utricle is believed to be an organ protecting the zygote against dessication. We interpret the morphological similarities between Paleozoic Sycidiales and Mesozoic Clavatoraceae, both with a utricle, as homoplasous rather than expressing a true phylogenetic relationship. We confirm that some umbellids might correspond to utricles of charophytes.

Charophyte algae from the Rhynie chert

The discovery of new specimens of Palaeonitella cranii (Kidston & Lang) Pia in the Early Devonian Rhynie chert permits the classification of this charophyte alga. This relatively small charophyte is composed of multicellular furcating branchlets with antheridia attached to the parent plant by a pedicel. The non-calcified gyrogonites, which are not seen in life position, are composed of six sinistrally spiralling cells and have six coronula cells arranged in a single layer around an apical pore. Because the oogonia of P. cranii have six sinistrally spiralling cells and an apical pore, Palaeonitella has been assigned to the Palaeocharaceae. The shape and form of the oogonia is reminiscent of the extant Chareae, but the morphology of the thalli is indicative of the Nitelleae. This suggests that P. cranii , although retaining some characteristics of the Nitelleae, has some of the characteristics of the Chareae, supporting existing molecular studies which place the Nitelleae at the base of the Characeae. Palaeonitella cranii inhabited the freshwater alkaline pools and streams which formed on sinter aprons created by hot spring activity. Extant charophytes exist in a similar environment (pH 8·66–8·9, temperature 25–30°C in summer) in pools and channels fed by hot springs in Yellowstone National Park, Wyoming, USA.

Nouvelles datations (Hauterivien supérieur–Barrémien inférieur) dans les « Couches rouges » continentales du Haut Atlas central marocain ; conséquences sur l’âge du magmatisme et des structurations mésozoïques de la chaîne Atlasique

Abstract In the Moroccan Central High Atlas, between the Bathonian and the Aptian, marine deposits are present in three continental formations. Known to be unfossiliferous for the main part, they are attributed to the Middle Jurassic or to the Lower Cretaceous, depending on the authors. Charophytes from the top of the second formation (Iouaridene Fm), and from the base of the third one (Jbel Sidal Formation), give an Upper Hauterivian–Lower Barremian age. Thanks to these biostratigraphical data, it has been possible to distinguish the different phases of the magmatic activity and the synsedimentary tectonic events, either linked to the closure of Tethyan Atlasic troughs during the Bathonian or associated with the development of the new basins, diachronous in the Atlasic Belt, during the Lower Cretaceous.

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.

Les oeufs de dinosaures du Cretace superieur du bassin de Villeveyrac-Meze (Herault, France); description d'une nouvelle ooespece de Prismatoolithus

The dinosaurian eggshell localities, found recently in the Villeveyrac-Meze basin allow to precise the datation of the continental levels overlaying the Villeveyrac Campanian series. They also provide information on the oospecies diversity in the Campano-Maastrichtian of southern France. Seven Megaloolithidae species which are already known in the Aix basin have been identified as well as a new prismatoolithid species, Prismatoolithus caboti.

New charophytes from the Upper Jurassic of the Lusitanian Basin (Portugal)

In the Lusitanian Basin (west-central Portugal), Upper Jurassic (Oxfordian) sediments were investigated in order to identify palaeontological assemblages of charophytes. Systematic studies were undertaken on specimens obtained from four field sections (Pedrógão, Vale de Ventos, Memória and Valverde). These studies revealed the presence of new forms of Porocharaceae (Porochara pedunculata n. sp) and of forms previously unknown in this region (Auerbachichara cf. saidakovskyi), as well as P. raskyae, P. minima, P. fusca, P. sulcata, P. kimmeridgensis, Aclistochara longiformis and Porochara sp. Comparison of the charophyte palaeofloras recognized in all of the studied sections has allowed the definition of three different assemblages which, coupled with other data, help to correlate these successions of Early (?) to Middle (Late?) Oxfordian age.

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.

Correlation of charophyte assemblages from the nonmarine Jurassic-Cretaceous transition of NW Germany

Abstract Based upon the first detailed study of the charophytes from the complete Upper Jurassic-lowermost Cretaceous (partly nonmarine) sequence of NW Germany, we distinguish eight successive assemblages which can be used as a local biozonation for the Lower Saxonian basin. Though charophytes cannot yet contribute to refined biozonations from the Oxfordian Korallenoolith up to the Tithonian Unterer Munder Mergel (assemblages 1–3) and in the late Berriasian-early Valanginian Wealden (assemblage 8), if compared with traditional ostracod/foraminifer biozones or palynozones, they are as useful as ostracods at the Jurassic-Cretaceous boundary (assemblages 4–5) and even better for correlation of the early Berriasian Serpulit and Purbeck (assemblages 6–7). Among other useful clavatoraceans, taxa principally from the Globator lineage present both short stratigraphic ranges and a large geographic distribution allowing: (a) the correlation of at least parts of the British lower Purbeck with the German Oberer Munder Mergel, Serpulit and Purbeck; (b) confirmation of the position of the Jurassic-Cretaceous boundary near the base of the Oberer Munder Mergel, as already proposed by ostracod workers; and (c) presentation of a more refined correlation of the assemblages from the Oberer Munder Mergel and Serpulit (Boreal realm) with the Early Berriasian biozones of the French and Swiss Jura (Tethyan realm).

Revision of Late Tithonian charophytes from Lisbon and Sintra-Cascais (Portugal): taxonomy, biostratigraphy and palaeobiogeographical significance

The re-evaluation of the charophyte content of ‘Purbeckian’ sediments from several sections around Lisbon (Olelas and Brouco) and Sintra-Cascais (Murches, Atrozela and Malveira-Guincho) revealed new palaeofloral associations from the Late Tithonian of the South Lusitanian Basin (Portugal). These sections contain Globator rectispirale, G. aff. nurrensis, Nodosoclavator bradleyi, Clavator reidi, Clypeator cf. discordis, Porochara maxima, and newly described occurrences of P. jaccardi, Mesochara harrisi and nodosoclavatoroide utricles. These revised data reinforce the evidence for assigning most of the studied deposits to a Late Tithonian age, instead of the formerly accepted wider interval Tithonian to Early Berriasian (‘Purbeckian’). Population analysis and statistics were applied in order to better assess population variation of the different species. The results of this study are relevant as they contribute to improve the biostratigraphical definition of the ‘Purbeckian’ formations of Portugal and allow more accurate palaeobiogeographical interpretations within the central Tethyan domain, by comparison of the identified charophyte assemblages with documented Jurassic–Cretaceous transition charophytes from other regions.

On the oldest representative of the family Characeae and its relationships with the Porocharaceae

SummaryThe paper records the discovery of the oldest representative of the family Characeae, Aclistochara aff. jonesi, in the Liassic freshwater Kota Formation, Gondwana Group of the Pranhita-Godavari Valley, Peninsular India. The species occurs in lime- mud sediments which are considered as having been deposited in brackish-water lakes with periodic oscillations of water-level under arid conditions. From the palaeontological point of view, the closure of the apex by the ends of the calcified spiral cells is interpreted as a xerophytic structure allowing the plant to persist during intervals of dessication. The increase of the average diameter of the apical pore of germination from Porochara to Aclistochara and Lamprothamnium is demonstrated.