Résumé
Together with Elkinsia and Condrusia, Moresnetia is one of the earliest hydrasperman Devonian seed. In contrast with most Devonian seed plants, our collection of Moresnetiafrom Belgium includes a large number of articulated specimens. Before this work, only the distal fertile parts of the plant had been described in detail, but our specimens have allowed us to study the branching pattern and three dimensional organisation of the plant. The first part of this study is based on ten specimens selected for their large dimensions and extensive branching. Classical camera lucida reconstructions have been attempted on these specimens. Furthermore, the size of the sample allowed us to do a numerical reconstruction of the plant. Several parameters have been measured such as the length and width of the axes and inner and outer angles of the ramifications. The modelling is still under progress, but preliminary results are presented here. Anatomy and morphology of the vegetative parts of the plant are still unknown, but we have obtained accurate anatomical information from the stem and the fertile axes preserved as goethite/limonite mineralisations. The stem shows a three-ribbed protostele with mesarch protoxylem strands. C-shaped vascular bundles of the Lyginorachis-type are produced at the tips of the ribs, according to a helical pattern. These bundles divide up to 9 times dichotomously, but not cruciately. Distalmost branches of the fertile frond show a single terete vascular strand. This anatomy is consistent with that observed earlier for Elkinsia polymorpha and Laceya hibernica.