Anne-Laure Decombeix

Quantitative wood anatomy requires precise measurement of wood cells. This step is often laborious and limiting for further analysis. We introduce Samwood, a tool based on the zero-shot Segment-Anything Model to easily segment cells on microscopic images without the need for a training dataset. The reconstruction of cell files then allows for the analysis of wood along growth orientation and precise measurement of anatomical properties of the wood, such as lumen areas. We tested our pipeline on an example dataset of fossil woods featuring deformation, heterogeneous preservation, and frequent artefacts, to assess the robustness of our approach. The model achieves a precision of 0.78 and a recall of 0.80, often producing segmentation of better quality and more consistent than a human operator. This approach substantially reduces analysis time, minimizes operator bias, and provides a robust and extensible framework for large-scale anatomical studies The complete code pipeline is available at https://github.com/umr-amap/samwood . GRAPHICAL

Premise: The Glossopteridales are an extinct group of seed plants that dominated mid to high latitude floras of the supercontinent Gondwana during the Permian (298–251 million years ago). Reconstructing their functional ecology is thus of particular importance for understanding the forests of that time period. Previous studies have shown evidence for diverse strategies favoring individual persistence and regeneration in glosssopterids. This evidence includes the production of epicormic and basal shoots, but there is no evidence of root suckering (i.e., new shoots from the root system). Methods: In previously made serial acetate peels on sections of silicified peat blocks from the late Permian of Skaar Ridge, Central Transantarctic Mountains, Antarctica, we identified two young glossopterid roots emitting a lateral axis with a non‐root anatomy and studied their anatomy. Results: The two specimens show evidence of young Vertebraria roots producing stem‐like laterals, which we interpret as evidence of root suckering. Conclusions: The specimens provide new evidence in favor of high ecological resilience among glossopterids and suggest that some may have had the potential for clonal growth. This example is the oldest to date of root suckering in a fossil plant.

The complexity of fossil forest ecosystems is difficult to reconstruct due to the fragmentary nature of the fossil record. However, detailed morpho-anatomical studies of well-preserved individual fossils can provide key information on tree growth and ecology, including in biomes with no modern analogue, such as the lush forests that developed in the polar regions during past greenhouse climatic episodes. We describe an unusual-looking stem from Middle Triassic (~240 Ma) deposits of Antarctica with over 100 very narrow growth rings and conspicuous persistent vascular traces through the wood. Sections of the specimen were prepared using the cellulose acetate peel technique to determine its systematic affinities and analyse its growth. The new fossil shows similarities to the form genus Woodworthia and with conifer stems from the Triassic of Antarctica, and is assigned to the conifers. Vascular traces are interpreted as those of small branches retained on the trunk. Growth-ring analyses reveal one of the slowest growth rates reported in the fossil record, with an average of 0.2 mm per season. While the tree was growing within the Triassic polar circle, sedimentological data and growth-ring information from other fossil trees, including from the same locality, support the presence of favourable conditions in the region. The specimen is interpreted as a dwarf conifer tree that grew under a generally favourable regional climate but whose growth was suppressed due to stressful local site conditions. This is the first time that a tree with suppressed growth is identified as such in the fossil record, providing new insights on the structure of polar forests under greenhouse climates and, more generally, on the complexity of tree communities in deep time.

The first anatomically preserved wood specimens of an upland Carboniferous flora from the Iberian Peninsula are reported from the Erillcastell Basin (Eastern Pyrenees, Catalonia, Spain). Two taxa are described, a calamitacean Equisetales (Arthropitys sp.) and a Cordaitales (Dadoxylon sp.). The Arthropitys specimen has fusiform multiseriate rays composed of square parenchyma cells with conspicuous uniseriate or multiseriate simple pits. These pits are located near the transverse walls and occasionally in the tangential walls. The tracheids vary in lumen size, with scalariform‐bordered pits on their radial walls and multiseriate pits in their cross‐field areas. The Dadoxylon specimen commonly has uniseriate fusiform rays. The tracheids are long, with a square shape in transverse section. Their radial walls bear araucarian pitting with a uniseriate to triseriate arrangement. The pits are circular with a spindle‐shaped aperture. Comparison of the Erillcastell specimens with coeval species from Europe indicates that they could belong to new species. The good preservation of the new fossil wood yields significant palaeoenvironmental information. The lack of marked growth rings in both specimens and the presence of tyloses in Dadoxylon suggest that the climate in the intramontane basins of the Pyrenees was slightly seasonal towards the end of the Carboniferous. This contrasts with the marked seasonality of coeval lowland basins. Such upland habitats may have enhanced the survival of plants adapted to humid conditions in a global context of increasing aridity.

The Jurassic vegetation of Antarctica remains poorly known and, while there have been several reports of large fossil trees from that time period across the continent, detailed anatomical studies of their wood are extremely scarce. Here we describe new silicified woods of Early Jurassic (probably Toarcian) age from Carapace Nunatak, South Victoria Land. The generaAgathoxylonandBrachyoxylonare formally recognized for the first time in the Jurassic of Antarctica. The preservation of the woods is imperfect, which is likely explained by the presence in some of the specimens of fungi, whose anatomical structures are described in detail. Combined with previous reports of pollen, leaves, and cones from South and North Victoria Land, these new specimens support the presence of several conifer families in the Early Jurassic floras of the region.

Tyloses are swellings of parenchyma cells into adjacent water-conducting cells that develop in vascular plants as part of heartwood formation or specifically in response to embolism and pathogen infection. Here we document tyloses in Late Devonian (approximately 360 Myr ago) Callixylon wood. This discovery suggests that some of the earliest woody trees were already capable of protecting their vascular system by occluding individual conducting cells.

Trouvez l'article de fascicule New Pitus and Eristophyton-type woods from the Tournaisian of Queensland, Australia: taxonomic, biogeographic, and palaeoclimatic implications sur le site des Publications scientifiques du Muséum national d'Histoire naturelle, Paris