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Premise of research. Mesozoic to Cenozoic fungi forming scutella, shield-like coverings of sporulating tissue on leaf surfaces, offer insights into the diversification of filamentous ascomycetes. We found a new fungal sporocarp type consisting of radiate scutella growing from the stomata of leaves of a conifer in a survey of dispersed plant cuticles from the Lower Cretaceous of Virginia. Here, we interpret the new morphotype and compare it with other fossil groups and with extant taxa. Methodology. We isolated fragments of conifer cuticles colonized by the fungus from macerated clays of the Potomac Group, lower Zone 1 (Aptian, 125–113 Ma), and studied them using light microscopy. We analyzed the anatomy of scutella of living taxa and compared the fossils with extant taxa producing either rhizothyria, asexual sporocarps that release spores from below the outer edge of the scutellum, or thyriothecia, sporocarps that release spores through dorsal cracks or an ostiole. Pivotal results. Stomatothyrium placocentrum gen. et sp. nov. has a radial arrangement of scutellum hyphae, characteristic of extant and fossil thyriothecial species in Dothideomycetes (Ascomycota). The scutella develop cracks on the dorsal surface that may show the dehiscence mechanism. Unusually for dehiscence in Dothideomycetes, the cracks follow the scutellum circumference rather than its radius. Each scutellum arises from a host plant stoma, appearing first as a hyphal columella that broadens into a flat scutellum disk on the leaf surface. The morphotype is common, and we found more than 63 specimens at different developmental stages on cuticle fragments. Conclusions. Its unique morphology suggests that S. placocentrum gen. et sp. nov. represents a now extinct group of leaf-dwelling Dothideomycetes that formed thyriothecia. This discovery contributes to our understanding of the range of character combinations of early epiphyllous Ascomycota. [ABSTRACT FROM AUTHOR]

A single cylindrical seed cone 2 cm long, 1.1 cm wide has been found preserved in a calcium carbonate marine concretion from the Hakobuchi Formation (late Campanian-early Maastrichtian) of Hobetsu, Hokkaido, Japan. The cone, attached to a bent peduncle lacking leaves, has helically arranged bract/scale complexes that arise at right angles from the cone axis in the middle of the cone. The cone axis, ca. 1 mm wide, has a broad cylinder of secondary vascular tissue, and lacks a continuous resin canal system. Bract-scale complexes are laminar, cordate-orbiculate, and upturned distally, consisting primarily of bract tissue with no visible scale tip. The vascular trace to the bract/scale complex originates as a rod that divides laterally into several traces at the level of seed attachment. A single resin canal originates at the base of the bract-scale complex abaxial to the vascular strand, but more distally there are up to ca. 15 large resin canals that form a single row. Two to three inverted winged seeds are attached adaxially near the cone periphery. Cone structure and vascularization are most similar to those in the Cupressaceae, Subfamily Taiwanioideae, differing from living Taiwania cryptomerioides by having up to three seeds/scale rather than two, an abruptly upturned bract tip, in details of bract/scale vasculature, and a cone peduncle lacking leaves. This cone is described as Mukawastrobus satoi Stockey, Nishida and Rothwell. Together with previously described Early to Late Cretaceous taiwanioid seed cones from Mongolia and Hokkaido the new species demonstrates that the taxonomically diagnostic characters of such conifers are as subtle as those of Cretaceous and Cenozoic sequoioid Cupressaceae. This realization emphasizes that evolutionary diversification and turnover among taiwanioid conifers during the Cretaceous and Paleogene are probably far greater than currently recognized. [ABSTRACT FROM AUTHOR]

Premise of research. A single cylindrical conifer seed cone has been discovered in a calcium carbonate marine concretion from the Upper Cretaceous Eden Main Quarry, dated as early Coniacian (∼89 Ma), 35 km northwest of Courtenay on Vancouver Island, British Columbia, Canada. Methodology. The specimen was sectioned with a rock saw, and serial sections were prepared using the classical cellulose acetate peel technique. Peel sections were mounted on microscope slides. Reconstructions of the cone and seeds were rendered with Avizo. Pivotal results. The cone is somewhat abraded, at least 2.3 cm long and 1 cm wide, with the apex missing and most of the base coalified. The well-preserved midsection shows bract/scale complexes inserted at a steep angle. The bract/scale complex has a central rhomboidal shaft and two lateral winglike extensions. Xylem of the cone axis is robust, with secondary xylem tracheids that have circular-bordered pits. A single circular vascular trace enters the bract/scale complex. Three resin canals enter the base of the scale and divide to form up to eight or nine canals distally. Six overlapping, inverted winged seeds, ∼8 mm long and 1 mm thick, with two large, fleshy wings are borne on the adaxial surface of each scale. The nucellus is free from the endotesta to its base. Megagametophytes and embryos occur in some seeds. Cells of the megagametophyte have granular contents. This cone shows similarities in overall structure and vasculature to those of living Taiwania (Cupressaceae); however, the fossil cone size is generally larger, with six seeds per scale versus two, and seeds are extremely large and fleshy with a unique submicropylar structure. Conclusions. This cone is compared with living and fossil taxa of Cupressaceae and described as Comoxostrobus rossii gen. et sp. nov. (Cupressaceae subfamily Taiwanioideae), revealing that taiwanioid Cupressaceae were much more diverse and widespread during the Cretaceous. [ABSTRACT FROM AUTHOR]

Premise of research. The occurrence of six ovulate cones and six leafy branching systems, two of which show attachment of the ovulate cone, reveals a new cunninghamioid fossil conifer from the Cretaceous Apple Bay locality of Vancouver Island, Canada. This anatomically preserved plant expands our understanding of basal Cupressaceae in the fossil record. Methodology. Specimens were studied from anatomical sections prepared by the classic cellulose acetate peel technique. Pivotal results. Vegetative shoots have helically arranged Cunninghamia-like leaves with a single vascular bundle and one to three resin canals. Ovulate cones consist of numerous helically arranged bract/scale complexes with a large bract and a small ovuliferous scale with three separate tips. There are three inverted seeds/ ovules attached adaxially, immediately proximal to the free scale tips. Conclusions. This discovery reveals the presence of a new genus and species of basal Cupressaceae, Hubbardiastrobus cunninghamioides, in the Early Cretaceous (Valanginian; ~136 Ma) of the Northern Hemisphere. These data expand the species richness of fossil Cupressaceae and further document the Cretaceous evolutionary radiation of subfamily Cunninghamioideae. [ABSTRACT FROM AUTHOR]

A diverse assemblage of fossil conifer leaves was identified in calcareous marine concretions from the Lower Cretaceous (Valanginian–Hauterivian) Apple Bay locality, Vancouver Island. Of the hundreds of isolated leaf fragments, most show affinities to Pinaceae. Leaves with closest similarities to Picea (spruce) were studied using cellulose acetate peels. Picea-like leaves vary in cross-section from rhomboidal, pentagonal, triangular, to ovoid. One fused vascular bundle with a centrally located ray and abaxial sclerenchyma is surrounded by a circular endodermis and transfusion tissue. Mesophyll is plicate containing two lateral external resin canals surrounded by a sclerenchyma sheath. Hypodermal fibres are one to three layers thick, except in areas of stomata. Leaves are amphistomatic, with sunken guard cells. Vascular bundles are identical anatomically to Picea; however, plicate mesophyll is similar to that in leaves of Pinus. Extensive sclerenchyma in the hypodermis and surrounding resin canals differs from that in most extant Picea. The major difference between these leaves and those of Picea is leaf shape. These fossil leaves probably belong to an extinct pinaceous conifer, and are described as Midoriphyllum piceoides gen. et sp. nov. Similar evidence from Cretaceous seed cones suggests that like the angiosperms, the Pinaceae were undergoing rapid mosaic evolution during the Lower Cretaceous. [ABSTRACT FROM AUTHOR]

Examines the cuticle micromorphology of leaves of the conifer genus Podocarpus from South Africa and Madagascar. Comparison of the external and internal features of abaxial and adaxial cuticles to other known Podocarpus species; Occurrence and description of the stomata; Characteristics to distinguish the different species.