Nouveaux specimens du genre Leclercqia Banks, H.P., Bonamo, P.M. et Grierson, J.D., 1972, du Givetien ( ? ) Du Queensland (Australie)

Axis fragments with « protolepidodendroid » surface pattern from the Middle Devonian (Givetian ?) of the Burdekin Basin (Queensland, Australia)are assigned, following their preparation to the genus Leclercqia,BANKS, H. P., BONAMO, P. M. et GRIERSON, J . D., 1972, formerly restricted to North America

Earliest land plants created modern levels of atmospheric oxygen

The progressive oxygenation of the Earth’s atmosphere was pivotal to the evolution of life, but the puzzle of when and how atmospheric oxygen (O2) first approached modern levels (~21%) remains unresolved. Redox proxy data indicate the deep oceans were oxygenated during 435-392 Ma, and the appearance of fossil charcoal indicates O2>15-17% by 420-400 Ma. However, existing models have failed to predict oxygenation at this time. Here we show that the earliest plants, which colonized the land surface from ~470 Ma onwards, were responsible for this mid- Paleozoic oxygenation event, through greatly increasing global organic carbon burial – the net long-term source of O2. We use a trait-based ecophysiological model to predict that cryptogamic vegetation cover could have achieved ~30% of today’s global terrestrial net primary productivity by~445 Ma. Data from modern bryophytes suggests this plentiful early plant material had a much higher molar C:P ratio (~2000) than marine biomass (~100), such that a given weathering flux of phosphorus could support more organic carbon burial. Furthermore, recent experiments suggest that early plants selectively increased the flux of phosphorus (relative to alkalinity) weathered from rocks. Combining these effects in a model of long-term biogeochemical cycling, we reproduce a sustained +2‰ increase in the carbonate carbon isotope (δ13C) record by ~445 Ma, and predict a corresponding rise in O2 to present levels by 420-400 Ma, consistent with geochemical data. This oxygen rise represents a permanent shift in regulatory regime to one where fire-mediated negative feedbacks on organic carbon burial stabilise high O2 levels

Estinnophyton gracile gen. et sp. nov., a new name for specimens previously determined Protolepidodendron wahnbachense Kräusel & Weyland, from the Siegenian of Belgium

Estinnophyton gracile gen. et sp. nov. is established for plant remains from the Lower Siegenian of Estinnes-au-Mont (Belgium) which have been long confused with Protolepidodendron wahnbachense Kräusel & Weyland 1932, from the Siegenian of the Wahnbachtal (Germany). The distinctive features of the new genus are discussed as well as its possible relationship with Lycophytes and Sphenophyllales.Estinnophyton gracile gen. et sp. nov. est fondé pour désigner des restes végétaux du Siegenien Inférieur d'Estinnes-au-Mont (Belgique) qui furent longtemps confondus avec Protolepidodendron wahnbachense Kräusel & Weyland 1932, du Siegenien de la Wahnbachtal (Allemagne). Les caractères distinctifs du nouveau genre sont discutés ainsi que ses affinités éventuelles avec les Lycophytes et les Sphénophyllales.Fairon-Demaret M. Estinnophyton gracile gen. et sp. nov., a new name for specimens previously determined Protolepidodendron wahnbachense Kräusel & Weyland, from the Siegenian of Belgium. In: Bulletin de la Classe des sciences, tome 64, 1978. pp. 597-610

À propos de certains spécimens de Drepanophycus gaspianus (Dawson) Stockmans, F., 1939, du Dévonien inférieur de Belgique

Some specimens amongst those described by F. Crépin in 1875 and the same year, by A. Gilkinet (1875) are included in, or excluded from the synonymy of Drepanophycus gaspianus (Dawson) Stockmans, F., 1939. Thus their re-examination was required. It allowed to assert the assignation of F. Crépin's specimens to D. gaspianus and to set aside A. Gilkinet's specimen. On the other hand special attention is drawn on D. gaspianus leaves morphology.Certains spécimens, parmi ceux décrits par F. Crépin en 1875 et, la même année, par A. Gilkinet (1875) sont inclus, ou exclus de la synonymie de Drepanophycus gaspianus (Dawson) Stockmans, F., 1939. Leur réexamen s'imposait donc. Il a permis de justifier l'attribution des spécimens de F. Crépin au D. gaspianus et d'écarter celui étudié par A. Gilkinet. Par ailleurs, la morphologie des feuilles de D. gaspianus fait l'objet d'une attention particulière.Fairon-Demaret M. À propos de certains spécimens de Drepanophycus gaspianus (Dawson) Stockmans, F., 1939, du Dévonien inférieur de Belgique. In: Bulletin de la Classe des sciences, tome 63, 1977. pp. 781-790

Givetian-Frasnian phytogeography of Euramerica and Western Gondwana based on Miospore distribution.

peer reviewe

Givetian-Frasnian phytogeography of Euramerica and western Gondwana based on miospore distribution.

peer reviewe