Diversität, Funktionalität und Evolution von Medullosen: Interaktion von Vegetation und Klima in einem saisonal trockenem Habitat des frühen Perms
Zusammenfassung der Projektergebnisse
The current research fellowship was initiated to shed light on poorly known taxa of medullosan seed ferns (Pteridospermopsida), growing in seasonally-dry forests of the late Paleozoic (late Carboniferous – early Permian). Medullosans were already widely known from Carboniferous wet tropical lowland forests. However, their relatives of the seasonally-dry forest ecosystems, today found silicified (anatomically-preserved) at few localities in Central Europe, remained poorly investigated for more than 100 years. Thus, a review paper was published to close this gap of knowledge by presenting these enigmatic stem taxa to a broad international audience of palaeobotanists. Major result of the paper is that the medullosans of seasonally-dry forests were distinctly larger and more massive (much more wood in the stem) than their relatives of Carboniferous tropical lowland forests. They also exhibit a modified water and nutrient conducting system and possess extensive fronds with an exceptional leaf surface area. These differences are regarded as the result of an evolutionary process that has been driven by environmental forces and changes of the forest structure. The crown architecture described for the medullosans of seasonally-dry habitats is impressively shown by a three-dimensionally preserved crown with ten attached fronds, each up to 2.5 m long, from the Chemnitz Fossil Forest (early Permian age). From this specimen, a complete crown with parts of the stem was reconstructed during the DFG project, providing a detailed whole-plant reconstruction of a “typical” Medullosa, including organ connection of foliage, fronds and the anatomically-preserved upper stem. The plant reconstruction enables further investigations, which are aiming towards functionality, palaeoecology, and growth habit of the medullosans. During the DFG fellowship, the fossil plant delivered comprehensive data to develop a computer model with colleagues from the AMAP institute in Montpellier. The computer model is able to answer hypotheses, which can be tested based on plant architectural features. A detailed picture of the plant architecture of a “typical” Medullosa is further going to open doors leading to new fields of research in the field of palaeobotany. As a future perspective, it is planned to decipher biomass production rates, atmospheric CO2 consumption, water evapotranspiration potential and gas exchange rates of medullosans. These data could contribute to our poor knowledge on the composition of the palaeo-atmosphere and other palaeoclimate parameters of the late Paleozoic world in the early Permian. These studies are recently in preparation and will result in ongoing research during the following months and probably years. Besides these novel ideas leading to new horizons of experimental palaeobotany, the research work performed during the DFG fellowship in Montpellier will also contribute to knowledge in the more “classical” fields of fossil plant sciences. During the project, it turned out that a reinvestigation of the described fossil plant taxa is necessary. This work has already begun during the fellowship and shows that the diversity of medullosans is potentially higher than previously described. Description of new taxa and redescription of old taxa with new data for whole-plant reconstructions are going to be performed in a new scientific project. Another new scientific project could deal with the evolution of early seed plants to decipher the interrelation of medullosans and potential ancient cycads, which show several similarities to medullosans and were growing in the same habitats. The origin of cycads is still under debate, but could be related to the evolution of the medullosan seed ferns. New and old fossil material on ancient cycadophytes is available.
Projektbezogene Publikationen (Auswahl)
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2021. Medullosan seed ferns of seasonally-dry habitats: old and new perspectives on enigmatic elements of Late Pennsylvanian – early Permian intramontane basinal vegetation. Review of Palaeobotany and Palynology
Luthardt, L., Galtier, J., Meyer-Berthaud, B., Mencl, V., Rößler, R.
