On 7–9 July 2016, the palaeontological association Agora Paleobotanica organised its fourth international meeting. It took place at the National History Museum of Brussels and was attended by 45 delegates. This special volume of the Earth and Environmental Science Transactions of the Royal Society of Edinburgh compiles key papers presented at this meeting. The topics covered include a wide variety of Devonian to Miocene plant taxa, with exciting new data on both mega- and microfossils.

The Lower Devonian Posongchong Formation (Wenshan, Yunnan Province, southwestern China) consists of a series of continental deposits with an outstanding plant megafossil diversity. More than 20 years ago, this formation was interpreted as ‘Siegenian' (∼Pragian) in age based on palynology. However, such interpretation needs further evidence because of the known differences between the dispersed spore assemblages from South China and Euramerica/northwestern Gondwana. Here, we present new dispersed spore assemblages recently recovered from the Posongchong Formation. The isolated spore diversity is highly diverse, with 18 genera and 32 species. The recognised taxa include, among others, Ambitisporites avitus, Aneurospora conica, Aneurospora posongchongensis sp. nov., Aneurospora xujiachongensis, Apiculiretusispora plicata, Archaeozonotriletes chulus, Concentricosisporites agradabilis, Dibolisporites echinaceus, Emphanisporites rotatus, Gneudnaspora divellomedia, Latosporites ovalis, Retusotriletes triangulatus, Tetrahedraletes medinensis and Verrucosporites polygonalis, with Aneurospora and Retusotriletes being the most abundant forms. The known Posongchong palynoflora (previous spore data included) suggests that the Posongchong Formation assemblages can be correlated with the Pragian interval of the polygonalis–wetteldorfensis Oppel Zone (PoW). This age determination is supported by the presence of index species of PoW, such as Verrucosporites polygonalis, Dictyotriletes subgranifer and Camarozonotriletes parvus (sensu Steemans, 1989), the latter being known only from the Pragian of Belgium and Germany. Recent advances in the study of the marine faunas in the overlying sequences also indicate a Pragian age for the Posongchong Formation. This new investigation of the Posongchong palynoflora highlights differences of abundance at species level between the Gondwanan–Laurussian floras during the Early Devonian.

The morphology of sterile and fertile structures (terminal strobili) of the Upper Devonian heterosporous lycopsid Kossoviella timanica Petrosjan 1984 from northern Russia (North Timan) is re-described: the axes are dichotomously branched; sterile leaves are narrow with smooth margins; the transition from sterile axes to strobili is gradual; the strobili are narrow and cylindrical, occasionally dichotomously branched; sporophylls are long, lanceolate, with crenulated margins; megasporangia with thin, mostly destroyed, sporangium walls contain one or two tetrads of large megaspores without a gula; numerous microspore tetrads are present in the microsporangia; both mega- and microspores are cavate, with a two-layered sporoderm; the outer layer of the sporoderm of both mega- and microspores consists of a net of intertwined cylindrical elements; the inner layer of the megaspore sporoderm is a basal lamina; and the inner homogeneous layer of the microspore sporoderm is split into multilamellate zones near the arms of the proximal scar. A comparison between abortive and fertile megaspores, some of which apparently were not completely mature, allows us to hypothesise that the enlargement and lateral stretching of structural units of the sporoderm, and the spaces between them, took place during the final stages of ontogenesis of megaspores along with the additional accumulation of amorphous sporopollenin. Both layers of the megaspore sporoderm, as well as the cavity between them, developed early in the ontogenesis. Although Kossoviella timanica was certainly a unique Late Devonian plant, it bears some resemblance to the Givetian heterosporous, bisporangiate lycopsid Yuguangia ordinata in having dichotomously branching axes, sporophylls with spiny margins and strobili with proximal megasporangia and distal microsporangia. Kossoviella timanica is also similar to the Famennian bisporangiate lycopsid Bisporangiostrobus harrisii in lacking a ligula and in having dichotomously branching strobili with proximal megasporangia and distal microsporangia.

Archaeopterid trees were the main components of most Late Devonian forests. Their aerial axes characterised by a eustele with mesarch primary xylem strands, leaf traces departing radially from cauline bundles and secondary xylem tracheids with radial pits arranged in groups, are referred to the genus Callixylon Zalessky. The nineteen species of Callixylon described to date from North America, North Africa, Europe, Xinjiang and several parts of Russia range from the late Givetian to the Mississippian. In this paper, we describe a new species of Callixylon from two specimens collected in the Famennian locality of Mader el Mrakib in eastern Anti-Atlas. Callixylon wendtii sp. nov. is characterised by the presence of sclerotic nests in the pith, a new character for the genus. Its wood shows narrow rays of variable height, with unevenly distributed ray tracheids. Small vascular traces crossing the wood within the two innermost growth rings are interpreted as evidence for short-lived leaves. This discovery adds to the diversity of the genus Callixylon in an area of northern Gondwana that may have been favourable to the establishment of a diverse community of archaeopterid trees.

Documented evidence of fungi associated with Mesozoic ferns is exceedingly rare. Three different types of fungal remains occur in a portion of a small, permineralised fern stem of uncertain systematic affinities from the Triassic of Germany. Exquisite preservation of all internal tissues made it possible to map the spatial distribution of the fungi in several longitudinal and transverse sections. Narrow, intracellular hyphae extend through the entire cortex, while wide hyphae are concentrated in the cortical intercellular system adjacent to the stele and leaf traces. Hyphal swellings occur in the phloem and adjacent cortex, while moniliform hyphae (or chains of conidia) are present exclusively in parenchyma adjacent to the stele. No host response is recognisable, but host tissue preservation suggests that the fern was alive during fungal colonisation. The highest concentration of fungal remains occurs close to the stele and leaf traces, suggesting that the fungi either utilised the vascular tissues as an infection/colonisation pathway or extracted nutrients from these tissues. This study presents the first depiction of fungal distribution throughout a larger portion of a fossil plant. Although distribution maps are useful tools in assessing fungal associations in relatively small, fossil plants, preparing similar maps for larger and more complex fossils would certainly be difficult and extremely arduous.

Although there are reports of permineralised woods in Mesozoic and Cenozoic strata in Mexico, there are few palaeobotanical studies based on coniferous stems. Four taxa of fossil wood from three localities in Mexico are described at the anatomical level and identified taxonomically based on detailed comparisons with woods of extant and fossil taxa. Agathoxylon gilii sp. nov. and A. jericonse sp. nov. are determined from the Todos Santos Formation (Upper Jurassic), in Chiapas; A. parrensis sp. nov. is described from the Las Encinas Formation (Palaeocene) in Coahuila; and Taxodioxylon cabullensis sp. nov. corresponds with material from the Packard Shale Formation in Sonora. Dominance of Araucariaceae and Cupressaceae in this region during the Mesozoic and early Cenozoic is further supported by leaf records, but these materials may also represent other taxa, like Cheirolepidaceae, which may have araucarioid secondary xylem. Records of Brachyphyllum and/or Pagiophyllum, which may represent araucarioid or cheirolepidaceous taxa, and different cupressaceous leaves, have been collected in rocks of the same period in nearby formations. At present, the amalgamation of isolated organs to form one plant is uncertain and, thus, there is an open challenge to reconstruct the plants and better understand these extinct communities. The new fossil taxa will add to the diversity of extinct plants and conifer communities during the Mesozoic and early Cenozoic in low-latitude North America.

The feature distinguishing typical angiosperms from gymnosperms is that their ovules are enclosed before pollination. Bennettitales were formerly related to angiosperms because of the flower-like organisation of the former's reproductive organs. There is little information on how the naked ovules of Bennettitales became enclosed in angiosperms because fossil evidence for such a transition, if it exists, has not been described. Here, we report a reproductive organ, Zhangwuia gen. nov., from the Middle Jurassic of Inner Mongolia, China. Like many Bennettitales, the arrangement of the foliar parts around the female part in Zhangwuia demonstrates a resemblance to typical angiosperm flowers. It is noteworthy that the ovule is secluded from the exterior space in Zhangwuia, therefore implying the existence of angio-ovuly. Although Bennettitales have been related to angiosperms for more than a hundred years, their way of ovule-enclosing was not previously revealed. The discovery of Zhangwuia prompts a rethinking of the relationship between Bennettitales and angiosperms, as well as of the origin of angiosperms.

Evidence of herbivory on Laurasian Nymphaeaceae leaves from Lower Cretaceous (Upper Albian) deposits is presented for the first time. The types of damage on leaves consist of both hole feeding and margin feeding, which were found on foliar remains of the taxa Ploufolia cerciforme and Aquatifolia cf. fluitans. Within the first category of damage, the Damage Type 78 (DT78) type on Ploufolia leaves and type DT02 on Aquatifolia foliar lamina were recorded. The second category of damage has only been identified in Ploufolia leaves, and it corresponds to type DT12. The subsequent palaeoichnologic interpretation made it possible to compare these records with damage caused by the extant water lily pest to make a possible palaeoecological interpretation.

New evidence of the extinct tree fern of the genus Tempskya Corda from Albian deposits in western Eurasia (northeastern Spain) is presented. These plant fossil remains consist of several silicified false trunks measuring up to 1.20m long, some of which still preserve the apex. Rhizomes and petioles are more abundant in the apical zone of the false trunk. Some false trunks preserve charcoalified tissues that can be interpreted as evidence that palaeo-wildfires affected the false trunks several times from mostly the same direction. Sedimentological evidence suggests that the fern habitat was close to coastal, tidally influenced environments. These new fossils from the Albian of Spain fill the chronological and distributional gap of Tempskya that existed in Eurasia during the Early Cretaceous. Temporal and spatial changes in Tempskya distributions are proposed on several palaeogeographical maps.

A new locality with silicified permineralised plant megafossils is reported from the upper Turonian of Colombiers, Vienne, western France. The plant fossil assemblage consists of Geinitzia reichenbachii (Geinitz) Hollick et Jeffrey and ‘Lomatopteris' superstes Saporta. Whilst G. reichenbachii is a worldwide widespread Cretaceous conifer, ‘L.' superstes is reported in western France for the first time. The latter fossil shows bipinnately compound leaf, marginal teeth, one thick primary vein, pinnate secondary veins and faint, reticulate, narrower veins. Besides its fern-like gross morphology, these characters indicate that it most likely belongs to angiosperms and eudicots. The formation of silicified nodules bearing such fossils from the Cenomanian to the Coniacian of western France was previously attributed to the secondary silicification of limestones during Cenozoic climatic weathering episodes. However, based on both petrography and preservation evidence, we demonstrate that it was an endogenic process contemporaneous to the earliest stages of fossil diagenesis created by palaeoenvironmental and climatic conditions.

Icacinaceae Miers are a family of trees, shrubs, and lianas with a current pantropical distribution. The family is well known in the fossil record, especially from the Palaeogene of Europe and North America, with the modern genus Iodes being particularly well represented. Here, we describe five new species of Iodes based on fossil endocarps with horn-like protrusions from the late Palaeocene Rivecourt deposits (Oise, France). Moreover, we propose a new combination for Iodes israelii Soudry & Gregor, as Icacinicarytes israelii (Soudry & Gregor) Del Rio, Thomas & De Franceschi, because it lacks the diagnostic morphological and anatomical characters of the genus Iodes. The significance of papillae, which has been emphasised in the literature, is discussed in light of new data, and a more standardised system of terminology is proposed. Given that, among modern members of Iodes, horn-like protrusions are only known from Asian species; the fossils described here suggest an affinity between the late Palaeocene flora of Europe and the modern flora of Asia. Finally, this study represents the first detailed investigation of Icacinaceae from the Paris Basin, where palaeocarpology remains understudied.

A new flower preserved in amber in sediments of Simojovel de Allende, México, is identified as an extinct member of Staphyleaceae, a family of angiosperms consisting of only three genera (Staphylea, Turpinia and Euscaphis), which has a large and abundant fossil record and is today distributed over the Northern Hemisphere. Staphylea ochoterenae sp. nov. is the first record of a flower for this group, which is small, pedicelled, pentamer, bisexual, with sepals and petals with similar size, dorsifixed anthers and superior ovary. Furthermore, the presence of stamens with pubescent filaments allows close comparison with extant flowers of Staphylea bulmada and S. forresti, species currently growing in Asia. However, their different number of style (one vs. three) and the apparent lack of a floral disc distinguish them from S. ochoterenae. The presence of Staphyleaceae in southern Mexico ca. 23 to 15My ago is evidence of the long history of integration of vegetation in low-latitude North America, in which some lineages, such as Staphylea, could move southwards from high latitudes of the Northern Hemisphere, as part of the Boreotropical Flora. In Mexico it grew in association with tropical elements, as suggested by the fossil record of the area.