Premise of research. The flora of the Maywood Formation, one of only three Devonian floras previously recognized in western North America, is known only from a brief report focused on stratigraphy and has never been characterized in more detail. A detailed assessment of this flora and associated fossils has implications for the age and depositional environments of the Maywood Formation, and for Devonian plant biogeography. Methodology. Field work at the Cottonwood Canyon (Wyoming) exposure of the Maywood formation produced a measured section characterizing the sedimentology of the unit and samples that we analyzed for palynomorph, macrofloral, and faunal content using standard methods. Pivotal results. The palynological assemblage is dominated by archaeopterid progymnosperm spores, lacks unequivocally marine components, indicates low burial depth and temperature (c. 53°C) of the unit, and supports an early Frasnian age. Plant macro-and mesofossils including charcoal, adpressions, sporangia, and spore packages reflect a vegetation with quasi-monodominant archaeopterids but also including the parent plant of the seed-megaspore Spermasporites (for which the Cottonwood Canyon occurrence represents a geographic range extension). Scales indicate the presence of sarcopterygian and tetrapodomorph fishes. Sedimentary facies, palynofacies, and plant macrofossil taphonomy are consistent with a lagoon or lake margin environment on a carbonate platform, disconnected from the open marine realm. Conclusions. The arid carbonate platform of the western margin of early Frasnian Laurentia hosted a fire-prone vegetation cover heavily dominated by archaeopterid progymnosperms. The Maywood Formation preserves fossil assemblages reflecting this vegetation at Cottonwood Canyon (Wyoming), in lagoonal or lacustrine deposits that also host microconchid tubeworms and fish. The parent plant of the seedmegaspore Spermasporites, present in this vegetation, was widely distributed all across Euramerica.

Phylogenetic studies of conifers that involve morphology are hindered by gaps in the anatomical characterization of seed cones, a direct result of difficulties encountered in sectioning cones in mature stages, which are often hardened due to sclerification. Here, we compare the resolving power of three methods-paraffin sectioning, petrographic thin-sectioning, and X-ray microcomputed tomography (micro-CT)in documenting the morphology and anatomy of mature seed cones at different scales of detail. We use Taxodium as a case study, based on which we make recommendations on the complementarity of these methods, and we present a paraffin sectioning protocol for softening sclerified tissues. Paraffin sectioning, while providing high anatomical resolution, can only be used for small specimens, is labor-intensive, and hampered by hard tissues. Petrographic sectioning is fast and effective on larger specimens, but has low anatomical resolution and is limited to dry non-fleshy material. Micro-CT, if available, is fast, produces high resolution with no size limitations, and allows virtual sectioning and accurate 3D rendering; however, understanding of histology requires comparisons of CT images with results of the other methods. Although they overlap, each of the three methods provides unique insights on anatomy at different scales of detail. Thus, combining all three methods is ideal for producing high-quality data at all scales of anatomical and morphological detail.