Stan Wood had a gift for finding exceptional Early Carboniferous fossils. Among them are 32 type specimens. His discoveries significantly changed our understanding of the history of life on Earth. Many of the fossils he collected are on display in museums across the UK and the localities he discovered continue to yield important new material. Here we briefly review some of Stan Wood's key achievements and describe the legacy he left.

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.

Stan Wood was an exceptional fossil collector who, over a collecting career of more than 40 years, provided British palaeontology with an abundance and variety of new Carboniferous fossils, the like of which had not been collected since Victorian times. So, what made him a great collector? Here, with the help of Stan's family, his friends and colleagues, we try to provide the answer. There is no single factor that stands out, but a complex mixture of innate and learned behaviours that together produced a unique talent. Although he acquired an Open University degree in geology, Stan was largely self-taught as a collector and, in doing so, became an accomplished and confident field geologist. He was naturally curious, persistent and very observant, with a photographic memory. He was tough, very strong and enjoyed hard physical work. He was congenial, unorthodox and a calculated risk taker. He asked questions, tested ideas and had a healthy disregard for authority. He was systematic, kept detailed records and shared his discoveries. He not only loved collecting fossils but, in the process, discovered in himself the essential qualities of a true scientist.

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 Glasgow area has a combination of highly variable superficial deposits and a legacy of heavy industry, quarrying and mining. These factors create complex foundation and hydrological conditions, influencing the movement of contaminants through the subsurface and giving rise locally to unstable ground conditions. Digital geological three-dimensional models developed by the British Geological Survey are helping to resolve the complex geology underlying Glasgow, providing a key tool for planning and environmental management. The models, covering an area of 3200km2 to a depth of 1.2km, include glacial and post-glacial deposits and the underlying, faulted Carboniferous igneous and sedimentary rocks. Control data, including 95,000 boreholes, digital mine plans and published geological maps, were used in model development. Digital outputs from the models include maps of depth to key horizons, such as rockhead or depth to mine workings. The models have formed the basis for the development of site-scale high-resolution geological models and provide input data for a wide range of other applications from groundwater modelling to stochastic lithological modelling.

Tristychius arcuatus, from the late Viséan of Scotland, is known from numerous ironstone nodule-encased specimens. These are reinvestigated using computerised tomography (CT) scanning and 3-D digital reconstruction methods. CT scans of the neurocranium (braincase) corroborate many features of the existing reconstruction, but also reveal new details of the gross proportions, the external morphology and, for the first time, features of the internal morphology, including the otic skeletal labyrinth. The unusual position of the articulation for the palatoquadrate on the ventral surface of the postorbital process is confirmed, but the area for the hyoid articulation is relocated posteriorly and the configuration of nerve foramina within the orbit is changed. A preliminary phylogenetic hypothesis is offered, suggesting a place for Tristychius within a sequence of early branching events in the elasmobranch lineage. In this, Tristychius is not resolved as a hybodontid, but is instead a stem elasmobranch possibly related to genera such as Acronemus, and exemplifying anatomical conditions close to the base of the Euselachii. As such, the neurocranium of Tristychius offers important insight into a defining feature of these early members of the anatomically advanced elasmobranchs: the origin of specialised phonoreception.

Characterising the three-dimensional (3D) distribution of hydraulic conductivity and its variability in the shallow subsurface is fundamental to understanding groundwater behaviour and to developing conceptual and numerical groundwater models to manage the subsurface. However, directly measuring in situ hydraulic conductivity can be difficult and expensive and is rarely carried out with sufficient density in urban environments. In this study we model hydraulic conductivity for 603 sites in the unconsolidated Quaternary deposits underlying Glasgow using particle size distribution and density description widely available from geotechnical investigations. Six different models were applied and the MacDonald formula was found to be most applicable in this heterogeneous environment, comparing well with the few available in situ hydraulic conductivity data. The range of the calculated hydraulic conductivity values between the 5th and 95th percentile was 1.56×10–2–4.38mday–1 with a median of 2.26×10–1 mday–1. These modelled hydraulic conductivity data were used to develop a suite of stochastic 3D simulations conditioned to existing 3D representations of lithology. Ten per cent of the input data were excluded from the modelling process for use in a split-sample validation test, which demonstrated the effectiveness of this approach compared with non-spatial or lithologically unconstrained models. Our spatial model reduces the mean squared error between the estimated and observed values at the excluded data locations over those predicted using a simple homogeneous model by 73 %. The resulting 3D hydraulic conductivity model is of a much higher resolution than would have been possible from using only direct measurements, and will improve understanding of groundwater flow in Glasgow and reduce the spatial uncertainty of hydraulic parameters in groundwater process models. The methodology employed could be replicated in other regions where significant volumes of suitable geotechnical and site investigation data are available to predict ground conditions in areas with complex superficial deposits.

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.

The early tetrapod Crassigyrinus scoticus was a large aquatic predator from the mid Carboniferous (late Viséan or early Serpukovian) of Scotland, around 330 My in age. There are five main specimens with cranial remains: an articulated skeleton; two incomplete skulls; and two lower jaws. Crassigyrinus retains several apparently primitive features of the palatal dentition and lower jaw, and its phylogenetic position is disputed. A partial lower jaw resembling that of Crassigyrinus was discovered at Burnmouth in the Borders region of Scotland. The horizon in which it was found is dated as late Tournaisian, CM palynozone, around 350 My in age. Though it lacks dentition, the jaw preserves much of the postsplenial, angular and surangular, whose appearance externally and internally is almost identical to that of C. scoticus. Internally, the jaw shows a similarly limited extent of the suturing between the splenial series and the prearticular, a primitive condition. Externally, the type and distribution of dermal ornamentation closely matches that of C. scoticus, as does the deeply excavated and marginally positioned lateral line groove. As well as external and internal features, all specimens of C. scoticus are of similar skull size, though the Burnmouth jaw is somewhat smaller. If correctly attributable to Crassigyrinus, this specimen extends the existence of the genus by approximately 20 million years towards the base of the Carboniferous.

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.

Although many European cities use urban aquifers for water supply, groundwater from shallow urban aquifers is not widely exploited. Nevertheless, shallow urban groundwater is a key environmental resource – for example, in maintaining healthy urban river flows and attenuating some pollutants – and it can also be a threat, such as through groundwater flooding. However, shallow urban groundwater is frequently overlooked or ineffectively managed, in large part because it is often poorly understood. This paper demonstrates the need to improve understanding of the shallow groundwater system in a city where shallow groundwater is not widely abstracted and, consequently, relatively little groundwater data exist. Like many UK cities, Glasgow is underlain by complex unconsolidated Quaternary deposits, which form a heterogeneous shallow aquifer system that has been extensively impacted by urban activities, typical of a former industrial city. Balancing the potential benefits and risks of shallow groundwater in Glasgow requires a better understanding of Quaternary hydrogeology in order to support the transition to a more sustainable city. This paper presents an improved conceptual model of Glasgow's shallow groundwater system within a sequence of Quaternary deposits in the Clyde valley, drawing heavily on data collected during major site investigations for land development in the city. Postglacial Quaternary sediments in Glasgow form an elongate, variably thick (up to 30m) and variably permeable aquifer system. Aquifer units with high permeability and high storage capacity are partially separated by lower permeability, but still hydrogeologically active, units. Groundwater in the system is hydraulically connected with the River Clyde. Groundwater flow occurs both longitudinally down-valley and convergent from the edge of the valley aquifer towards the river. There has been extensive anthropogenic alteration to the urban surface and shallow subsurface, which has modified the natural physical and chemical groundwater system. Pollution associated with historical industry has also extensively impacted the quality of Quaternary groundwater.

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.

Glencartholm in Dumfries and Galloway, Southern Scotland, is one of the most important Palaeozoic fossil fish sites in the world, with a fauna containing more than 30 species. Originally discovered in the bank of the River Esk in 1879, further collecting in the 1930s removed all the accessible fossiliferous strata. These strata were not known to occur elsewhere and despite the site's international importance, details of the section including the fossil bearing beds have not been described. An excavation of a new exposure at Mumbie, 50 metres east of the original site, was undertaken by Stan Wood in the 1990s. Sediments were logged over an 18-metre section. Three separate fish beds were identified and more than 200 specimens of ray-finned fish collected, including one possible new species. Differences in scale colour enables fishes from the different horizons to be distinguished. This should allow material collected previously to be more accurately assigned and assist palaeoecological analysis of the site. In addition to ray-finned fish, cartilaginous fishes were collected together with plants, bivalves, crustaceans, scorpions and horseshoe crabs which have not previously been reported from Glencartholm.

A new GIS-based screening tool to assess threats to shallow groundwater quality has been trialled in Glasgow, UK. The GRoundwater And Soil Pollutants (GRASP) tool is based on a British Standard method for assessing the threat from potential leaching of metal pollutants in unsaturated soil/superficial materials to shallow groundwater, using data on soil and Quaternary deposit properties, climate and depth to groundwater. GRASP breaks new ground by also incorporating a new Glasgow-wide soil chemistry dataset. GRASP considers eight metals, including chromium, lead and nickel at 1622 soil sample locations. The final output is a map to aid urban management, which highlights areas where shallow groundwater quality may be at risk from current and future surface pollutants. The tool indicated that 13% of soil sample sites in Glasgow present a very high potential threat to groundwater quality, due largely to shallow groundwater depths and high soil metal concentrations. Initial attempts to validate GRASP revealed partial spatial coincidence between the GRASP threat ranks (low, moderate, high and very high) and groundwater chemistry, with statistical correlation between areas of high soil and groundwater metal concentrations for both Cr and Cu (r2>0.152; P<0.05). Validation was hampered by a lack of, and inconsistency in, existing groundwater chemistry data. To address this, standardised subsurface data collection networks have been trialled recently in Glasgow. It is recommended that, once available, new groundwater depth and chemistry information from these networks is used to validate the GRASP model further.

The first half of the Mississippian or Early Carboniferous (Tournaisian to mid- Viséan), an interval of about 20 million years, has become known as “Romer's Gap” because of its poor tetrapod record. Recent discoveries emphasise the differences between pre-“Gap” Devonian tetrapods, unambiguous stem-group members retaining numerous “fish” characters indicative of an at least partially aquatic lifestyle, and post-“Gap” Carboniferous tetrapods, which are far more diverse and include fully terrestrial representatives of the main crown-group lineages. It seems that “Romer's Gap” coincided with the cladogenetic events leading to the origin of the tetrapod crown group. Here, we describe a partial right lower jaw ramus of a tetrapod from the late Tournaisian or early Viséan of Scotland. The large and robust jaw displays a distinctive character combination, including a significant mesial lamina of the strongly sculptured angular, an open sulcus for the mandibular lateral line, a non-ossified narrow Meckelian exposure, a well-defined dorsal longitudinal denticle ridge on the prearticular, and a mesially open adductor fossa. A phylogenetic analysis places this specimen in a trichotomy with Crassigyrinus and baphetids + higher tetrapods in the upper part of the tetrapod stem group, above Whatcheeria, Pederpes, Ossinodus, Sigournea and Greererpeton. It represents a small but significant step in the gradual closure of “Romer's Gap”.

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.

An assessment of topsoil (5–20cm) metal/metalloid (hereafter referred to as metal) concentrations across Glasgow and the Clyde Basin reveals that copper, molybdenum, nickel, lead, antimony and zinc show the greatest enrichment in urban versus rural topsoil (elevated 1.7–2.1 times; based on median values). This is a typical indicator suite of urban pollution also found in other cities. Similarly, arsenic, cadmium and lead are elevated 3.2–4.3 times the rural background concentrations in topsoil from the former Leadhills mining area. Moorlands show typical organic-soil geochemical signatures, with significantly lower (P<0.05) concentrations of geogenic elements such as chromium, copper, nickel, molybdenum and zinc, but higher levels of cadmium, lead and selenium than most other land uses due to atmospheric deposition/trapping of these substances in peat. In farmland, 14% of nickel and 7% of zinc in topsoil samples exceed agricultural maximum admissible concentrations, and may be sensitive to sewage-sludge application. Conversely, 5% of copper, 17% of selenium and 96% of pH in farmland topsoil samples are below recommended agricultural production thresholds. Significant proportions of topsoil samples exceed the most precautionary (residential/allotment) human-exposure soil guidelines for chromium (18% urban; 10% rural), lead (76% urban; 45% rural) and vanadium (87% urban; 56% rural). For chromium, this reflects volcanic bedrock and the history of chromite ore processing in the region. However, very few soil types are likely to exceed new chromiumVI-based guidelines. The number of topsoil samples exceeding the guidelines for lead and vanadium highlight the need for further investigations and evidence to improve human soil-exposure risk assessments to better inform land contamination policy and regeneration.

The chemical composition of soil from the Glasgow (UK) urban area was used to identify the controls on the availability of potentially harmful elements (PHEs) in soil to humans. Total and bioaccessible concentrations of arsenic (As), chromium (Cr) and lead (Pb) in 27 soil samples, collected from different land uses, were coupled to information on their solid-phase partitioning derived from sequential extraction data. The total element concentrations in the soils were in the range <0.1–135mgkg–1 for As; 65–3680mgkg–1 for Cr and 126–2160mgkg–1 for Pb, with bioaccessible concentrations averaging 27, 5 and 27% of the total values, respectively. Land use does not appear to be a predictor of contamination; however, the history of the contamination is critically important. The Chemometric Identification of Substrates and Element Distribution (CISED) sequential chemical extraction and associated self-modelling mixture resolution analysis identified three sample groupings and 16 geochemically distinct phases (substrates). These were related to iron (n=3), aluminium–silicon (Al–Si; n=2), calcium (n=3), phosphorus (n=1), magnesium (Mg; n=3), manganese (n=1) and easily extractable (n=3), which was predominantly made up of sodium and sulphur. As, Cr and Pb were respectively found in 9, 10 and 12 of the identified phases, with bioaccessible As predominantly associated with easily extractable phases, bioaccessible Cr with the Mg-dominated phases and bioaccessible Pb with both the Mg-dominated and Al–Si phases. Using a combination of the Unified Barge Method to measure the bioaccessibility of PHEs and CISED to identify the geochemical sources has allowed a much better understanding of the complexity of PHE mobility in the Glasgow urban environment. This approach can be applied to other urban environments and cases of soil contamination, and made part of land-use planning.

Chondrichthyan teeth from a new locality in the Scottish Borders supply additional evidence of Early Carboniferous chondrichthyans in the UK. The interbedded dolostones and siltstones of the Ballagan Formation exposed along Whitrope Burn are interpreted as representing a restricted lagoonal environment that received significant amounts of land-derived sediment. This site is palynologically dated to the latest Tournaisian–early Viséan. The diverse dental fauna documented here is dominated by large crushing holocephalan toothplates, with very few, small non-crushing chondrichthyan teeth. Two new taxa are named and described. Our samples are consistent with worldwide evidence that chondrichthyan crushing faunas are common following the Hangenberg extinction event. The lagoonal habitat represented by Whitrope Burn may represent a temporary refugium that was host to a near-relict fauna dominated by large holocephalan chondrichthyans with crushing dentitions. Many of these had already become scarce in other localities by the Viséan and become extinct later in the Carboniferous. This fauna provides evidence of early endemism or niche separation within European chondrichthyan faunas at this time. This evidence points to a complex picture in which the diversity of durophagous chondrichthyans is controlled by narrow spatial shifts in niche availability over time.