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PREMISE Exceptional anatomical preservation of a fossil araucarian seed cone from a marine carbonate concretion from Vancouver Island, British Columbia, Canada provides unusually complete evidence for cone structure including seeds, megagametophytes, microgametophytes, and embryos of an Upper Cretaceous (Campanian) species of Araucaria, providing important new insights into the structure and relationships of Cretaceous Northern Hemisphere Araucariaceae. METHODS The cone was studied from serial thin sections prepared by the coal ball peel technique. Phylogenetic analysis using a modified morphological matrix with both discrete and continuous characters was performed using TNT version 1.5. RESULTS The nearly spherical cone, 6 × 6 cm in diameter, has helically arranged cone-scale complexes, consisting of a large bract with an upturned tip and a small, fleshy ovuliferous scale. Vascularization of the cone-scale complex is single at its origin. Widely winged bracts, with a bulging base, contain numerous vascular bundles, interspersed with transfusion tissue, and a large number of resin canals. Seeds are ovoid, 1.2 cm long, 1.2 cm in diameter. Nucellus is free from the integument, except at its base, with a convoluted apex, containing possible pollen tubes. Megagametophytes and mature cellular embryos occur in several seeds. CONCLUSIONS This small cone with attached, imbricate leaves, wide bracts, and unusually large seeds, most closely resembles those of Araucaria Section Eutacta. Width and continuity of secondary xylem in the cone axis, and intact cone-scale complexes indicate that this cone probably did not disarticulate readily at maturity. When added to a modified, previously published phylogenetic analysis, Araucaria famii sp. nov. enhances our understanding of the Cretaceous radiation of Northern Hemisphere Araucaria Section Eutacta.

Coal balls are calcium carbonate accumulations that permineralized peat in paleotropical Permo-Carboniferous (∼320–250 Ma) mires. The formation of coal balls has been debated for over a century yet a widely applicable model is lacking. Two observations have been particularly challenging to explain: 1) the narrow temporal occurrence of coal balls and 2) their typical elemental (high Mg) and isotopic (low δ18O) composition that paradoxically indicate marine and freshwater origins, respectively. We evaluate a new model in which coal balls formed as CO2 escaped from the peat by diffusion through unusual air-filled spaces in the rootlets of lycopsid trees; critically, these trees were very common in paleotropical mires, and their evolutionary range matches the temporal range of coal balls. The episodic delivery of seawater and marine carbonate sediment to coastal mires is the first step in our model, although other pathways for the delivery of divalent cations are permissible. Subsequent dilution by freshwater and dissolution of these carbonates at the elevated CO2 of the mire subsurface is followed by the transport of CO2 through the rootlet airspaces and into the overlying water and atmosphere, which drives carbonate mineral precipitation in the sediment. We show that dilution by freshwater, because it minimally affects Mg/Ca ratios, can result in relatively low pore water δ18O values while allowing high-Mg calcite formation. This model thus explains the restriction of coal balls to the Permo-Carboniferous and resolves the discrepancy between elemental and isotopic compositions of coal ball carbonate minerals. Furthermore, we show with a 3D reactive transport model that CO2 could escape rapidly enough through the rootlets to fill 25 percent of the peat pore spaces with calcite before substantial burial (top decimeter of peat), explaining the exceptional preservation of coal swamp flora. Therefore, we suggest that coal balls are pedogenic in origin and that the disappearance of these pedogenically permineralized Histosols represents the first documented decrease in soil diversity on a vegetated planet. The rock record may thus provide important context for the modern loss and degradation of soils.

From the perspective of Phanerozoic time, coal balls are rare, apparently limited to a 24 m.y. interval (323–299 Ma) in the Pennsylvanian and earliest Permian. Yet within this interval, coal balls occur in many coals. Approximately 82 transgressive-regressive sedimentary cycles have been described for the Midcontinent, Illinois and Appalachian basins of North America during the mid-to-late Pennsylvanian. One third (27/82) have coal balls, including 57% of major cycles, 36% of intermediate cycles and 16% of minor cycles. Coal-ball occurrence in the Donets Basin is similar: over an interval of about 4 m.y. (~315–311 Ma, latest Bashkirian to mid-Moscovian), 39% (11/28) of transgressive-regressive cycles have coal balls. As North American paleoclimate became drier, tree ferns replaced lycopsids as the dominant plant in peat swamps at the Desmoinesian/Missourian boundary, and coal-ball occurrence declined. Overall, 47% of cycles (19/40) with lycopsid or cordaitean dominance have coal balls, whereas 19% (8/42) of cycles with tree fern dominance have coal balls (p This pattern may reflect the relative abundance of coal in the Late Pennsylvanian, with drier paleotropical climates in the Missourian-Virgilian leading to less paleotropical coal, fewer mines and a lower probability of discovering Missourian and Virgilian coal balls. However, average cycle duration decreased from 150 kyr in the Desmoinesian to ~100 kyr in the Missourian and Virgilian, and faster rates of relative sea-level rise could have affected coal-ball abundance, particularly if coal balls formed in marine swamps, with more rapid transgression leading to thinner coals, or to freshwater coals directly overlain by marine sediments. Rygel et al. (2008) suggested that Missourian-Virgilian cycles recorded more erosional relief than Desmoinesian cycles, consistent with increased amplitude and rates of sea-level rise during each glacial-eustatic cycle. Changes in Missourian-Virgilian cycles may have been augmented by stratigraphic attenuation as sediment filled the antecedent topography.

This paper described a new early leptosporangiate fern occurring in the Lower Permian coal balls from Shanxi Province, North China. The fossil materials include stems, attached and detached petioles and roots, belonging to a same kind of plant. Stems are relatively small in diameter and branch dichotomously. They possess a haplostele with metaxylem tracheids decreasing outward in diameter and showing uniseriate scalariform thickenings. There are no distinguished protoxylem groups in the xylem cylinder. Cortex is parenchymatous and can be divided into three zones according to cell size. Petiolar traces bear different shapes in cross section and show a spiral diverging sequence. Petioles are circular in cross section and cortical cells are much smaller than those of stems. Petiolar traces and petioles possess a single protoxylem group at the adaxial side of the xylem strand. Root traces originate from the cauline stele and go through the cortex in a way perpendicular or oblique to the cauline stele. These characters show great similarities to the genus Rhabdoxylon but are not consistent with its any known species, so it is necessary to create a new species Rhabdoxylon taiyuanense n. sp. for the present plant. The new species probably possesses an upright habit. This is the first report of the existence of the genus Rhabdoxylon in the Cathaysian Flora. The discovery of a new type of the Palaeozoic leptosporangiate fern in China has led to reevaluation of the systematic relationships among species of the Botryopteridaceae.

Anatomically preserved botryopterid specimens from Cisuralian (early Permian) aged coal balls in Shanxi Province, North China are investigated. Stems are relatively small, branch dichotomously, and possess a haplostele with metaxylem tracheids showing uniseriate scalariform thickenings. Protoxylem groups are associated with the forming of the petiolar trace, and a parenchyma plate appears in the process of separating petiolar traces. The cortex consists of three parts, with inner and middle parenchymatous zones and an outer sclerenchymatous zone. Stems are radially organized and bear helically arranged petioles. Petioles extend from the stems in various orientations while adventitious roots extend through the cauline cortex perpendicular or oblique to the stem. Associated rachides are D-shaped in cross section and the xylem is slightly to conspicuously adaxially curved with 1 protoxylem ridge at each lateral margin. Differences with previously known genera of Botryopteridaceae lead to creation of new genus, Diodonopteris gracilis Ma et al. gen. nov. et sp. nov. that demonstrates features that overlap to some extent with those of previously known genera within Botryopteridaceae. The habit and growth forms of D. gracilis are considered. D. gracilis represents by far the best known plant of Botryopteridaceae recognized from the Cathaysian Flora.

Petrographic analyses of 25 coal balls from well-studied paleobotanical profiles in the Middle Pennsylvanian Herrin Coal (Westphalian D, Illinois Basin) and five select coal balls from university collections, indicate that Herrin Coal-ball peats were permineralized by fibrous and non-fibrous carbonates. Fibrous carbonates occur in fan-like to spherulitic arrays in many intracellular (within tissue) pores, and are best developed in relatively open extracellular (between plant) pore spaces. Acid etched fibrous carbonates appear white under reflected light and possess a microcrystalline texture attributable to abundant microdolomite. Scanning electron microscopy, X-ray diffraction, and electron microprobe analysis demonstrate that individual fibers have a distinct trigonal prism morphology and are notable for their magnesium content (≈ 9–15 mol% MgCO 3 ). Non-fibrous carbonates fill intercrystalline spaces among fibers and pores within the peat as primary precipitates and neomorphic replacements. In the immediate vicinity of plant cell walls, non-fibrous carbonates cut across fibrous carbonates as a secondary, neomorphic phase attributed to coalification of plant cell walls. Dolomite occurs as diagenetic microdolomite associated with the fibrous carbonate phase, as sparite replacements, and as void-filling cement. Maximum dolomite (50–59 wt.%) is in the top-of-seam coal-ball zone at the Sahara Mine, which is overlain by the marine Anna Shale. Coal-ball formation in the Herrin Coal began with the precipitation of fibrous high magnesium calcite. The trigonal prism morphology of the carbonate fibers suggests rapid precipitation from super-saturated, meteoric pore waters. Carbonate precipitation from marine waters is discounted on the basis of stratigraphic, paleobotanical, and stable isotopic evidence. Most non-fibrous carbonate is attributable to later diagenetic events, including void-fill replacements, recrystallization, and post-depositional fracture fills. Evidence suggests that CO 2 degassing was important in coal-ball formation in the Herrin Coal, which mainly occurred sequentially upward with peat accumulation in the sites studied.

Noeggerathiales are an extinct group of spore-bearing plants of uncertain systematic position that are known from Carboniferous and Permian age Euramerican and Cathaysian floras that occurred in present-day Europe, North America, and East Asia. The order Noeggerathiales includes over 50 species of more than 20 fossil genera, but their paleoecology is not well understood yet. Previously this group had been found only in extrabasinal floras or those inhabiting clastic wetlands. Noeggerathiales have never been recorded in coal ball floras. Thus, it is up to now uncertain whether this group has contributed to the formation of coal. Recent investigations of an Early Permian peat-forming flora of the Taiyuan Formation near Wuda, Inner Mongolia, which was preserved in a volcanic ash fall has provided evidence that noeggerathialean plants not only existed in the peat-forming vegetation but could even be the dominant group in some areas of the coal swamp. The Noeggerathiales in this particular peat-forming forest include Tingia unita, Paratingia wudensis, and a new species of Paratingia. Exceptionally well-preserved specimens indicate that these noeggerathialean plants are small trees with a canopy of compound leaves and strobili near the top of an unbranched (monocaulous) stem.

Premise of research. A third genus of anatomically preserved conifer seed cones has been recognized from a Late Jurassic deposit in northeastern Scotland. This cone is described as Bancroftiastrobus digitata Rothwell, Mapes, Stockey et Hilton.Methodology. The cone was sectioned with the classic coal ball peel technique and studied and photographed with transmission light.Pivotal results. Bancroftiastrobus digitata is a cylindrical cone with large, helically arranged ovuliferous scales subtended by short bracts, each bract/scale complex bearing two unwinged inverted seeds on the adaxial surface of the ovuliferous scale. Ovuliferous scales have abaxial plications in the midregion and divide distally, forming up to nine free distal lobes that are vascularized and covered by a dense ramentum of trichomes. The cone axis forms a continuous woody cylinder that surrounds a parenchymatous pith. There are numerous resin canals in the cortex of the cone axis that extend into each bract/scale complex, both abaxial an...

Anatomically preserved wood collected from coal seam no. 1 of the Naluozhai coal mine in the Lopingian (Late Permian) Wangjiazhai Formation in western Guizhou Province, China, is documented and interpreted. The wood belonged to a trunk with an inferred diameter of 25 cm or more and consists of axial tracheids and horizontal rays. Tracheids vary greatly in size, and small ones are usually irregularly arranged. Tracheid walls are 5–10 μm thick and usually bilayered. There are usually biseriate araucarioides-type bordered pits on the radial tracheid walls. Two to five oval bordered pits are in each cross-field. Ray cells are thin walled, although thick-walled cells exist in some rays. Rays are quite variable in width and height. Uni- and partly biseriate rays are usually 2–20 cells high, while bi- and partly tri- to tetraseriate ones are 5–79 cells high. The cell size of rays is also quite variable and is usually larger than that of tracheids in the tangential direction. There are numerous leaf trace...

Evidence of fossil Peronosporomycetes has been slow to accumulate. In this review various fossils historically assigned to the Peronosporomycetes are discussed briefly and an explanation is provided as to why the fossil record of this group has remained inconsistent. In recent years there have been several new reports of fossil peronosporomycetes based on structurally preserved oogonium-antheridium com- plexes from Devonian and Carboniferous rocks that demonstrate the existence of these organisms as fossils and refute the long-standing assumption that they are too delicate to be preserved. Among these are several types characterized by oogonial surface ornamentation patterns not seen in any modern members of the group. To date at least three groups of fossil vascular plants (i.e. lycophytes, ferns and seed ferns) are known to host peronosporomycetes as endophytes; however only one form has been identified as a parasite.

The mode of preservation dictates the preparation technique that will yield the most information about a specific fossil. Such considerations also include the time needed for preparation and degree of specimen destruction. Nowhere is this more clearly demonstrated than in the history of Carboniferous coal ball and chert research where the standard technique shifted from thin section to acetate peel preparations many years ago. Despite the ease and efficiency of acetate peels and the exponential increase in information they have provided about Carboniferous plants and ecosystems, we argue that there has been a concomitant decrease in attention directed at the microbial life also preserved in many cherts and coal balls. With this paper we endorse the use of thin sections, rather than peels, in order to study accurately the morphology and diversity of late Paleozoic microbial life.

Recent investigations into Permian aged floras from China have highlighted the widespread occurrence of callistophytalean pteridosperms that challenge previous understanding of their spatial and temporal distribution and diversity. In China, the group spans the Permian period and constitutes a distinctive but rare component in many peat- forming environments. The stratigraphically earliest calli- stophytalean occurs in the Asselian-Sakmarian stages with fossils from the Taiyuan Formation of northern China including ovules of Callospermarion undulatum in coal ball assemblages, and ovulate fronds of Norinosperma shanxiensis and synangiate fronds of Norinotheca shanxiensis in adpres- sion assemblages. More abundant in the fossil records are ad- pression remains from the Roadian-Wordian stages with the Lower Shihhotse Formation preserving abundant vegetative and ovulate remains of Emplectopteris triangularis that is now considered to represent a callistophytalean. The youngest callistophytalean recognised is from the Wuchaipingian- Changhsingian stages with the Xuanwei Formation of southern China containing a single stem of Callistophyton boyssetii that provides indisputable evidence of the group in the lead up to the end-Permian mass extinction. These accounts are augmented by analysis of pollen records that demonstrate the callistophytalean pollen genus Vesicaspora to be widespread through palynological assemblages from the Permian period in both North and South China, including the Upper Shihhotse Formation, Shihchienfeng Group, Xuanwei Formation, and possibly also in the mid-Pennsylva- nian Benxi Formation. Although macrofossil specimens are uncommon elements in the assemblages that contain them, they demonstrate the continuity of callistophytalean pterido- sperms from the Pennsylvanian sub-period into the early Guadalupian epoch of the Permian in North China and into the Lopingian epoch of the Permian in South China. Of the species present, both Callistophyton boyssetii and Callosper- marion undulatum are known from the Pennsylvanian-earli- est Permian age floras of Euramerica, whereas Norinosperma, Norinotheca and Emplectopteris appear to represent endemic Cathaysian elements. Results imply that callistophytalean pteridosperms can no longer be excluded from theories of post-Carboniferous plant evolution and floristics, appearing to have played an important role in both Permian and Car- boniferous aged plant communities. The presence of Vesicas- pora in several formations from which macro-remains have not been identified is a hopeful indicator that further calli- stophytalean pteridosperms are yet to be found.

Two alternative processes complicate understanding of the biochemical origins and geochemical alteration of organic matter over geologic time: selective preservation of original biopolymers and in situ generation of new geopolymers. One of the best constrained potential sources of bio- and geochemical information about extinct fossil plants is frequently overlooked. Permineralized anatomically preserved plant fossils allow analysis of individual cell and tissue types that have an original biochemical composition already known from living plants. The original composition of more enigmatic fossils can be constrained by geochemical comparisons to tissues of better understood fossils from the same locality. This strategy is possible using synchrotron-based techniques for submicron-scale imaging with X-rays over a range of frequencies in order to provide information concerning the relative abundance of different organic bonds with X-ray Absorption Near Edge Spectroscopy. In this study, X-ray PhotoElectron Emission spectroMicroscopy (X-PEEM) was used to analyze the tissues of Lepidodendron , one of the lycopsid trees that were canopy dominants of many Pennsylvanian coal swamp forests. Its periderm or bark—the single greatest biomass contributor to many Late Paleozoic coals—is found to have a greater aliphatic content and an overall greater density of organic matter than lignified wood. Because X-PEEM allows simultaneous analysis of organic matter and matrix calcite in fully mineralized fossils, this technique also has great potential for analysis of fossil preservation, including documentation of significant traces of organic matter entrained in the calcite crystal fabric that fills the cell lumens.

Marie Stopes (1880-1958) is chiefly remembered as a birth control pioneer and sexologist, but in her twenties and thirties she carved out a highly successful career as a palaeobotanist and coal geologist. This paper outlines her early geological research on coal balls—carbonate concretions found within the Carboniferous coal seams of northern England, which preserve the remains of the peat-forming plants in beautiful anatomical detail. Stopes worked on coal balls during three intervals of her career. In the first phase (early 1903), she was Francis Oliver's postgraduate research assistant at University College London, during the critical period leading up to the ‘discovery of pteridosperms’ with D. H. Scott. Stopes's role was to hunt down key specimens in coal ball collections scattered across Britain. In the second phase (late 1904-1907), which followed a year of doctoral research in Munich, she grappled with the more broad-ranging questions of the origin of coal balls, their stratigraphic distribution, and the taphonomy and ecology of the plants they contained. This work took place while she was a Demonstrator in Botany at the Victoria University of Manchester, and was undertaken in collaboration with David Watson. Their findings transformed understanding of coal ball origins and remain influential today. In the third phase (1907-1911), she searched for coal balls in other countries and other stratigraphic intervals. She explored Japan for coal balls of Mesozoic age (1907-early 1909), and although unsuccessful in this particular endeavour, later she became one of the first geologists to locate Carboniferous coal balls in North America in 1911.

Quantitative plant assemblage data from coal balls, miospores, megaspores, and compression floras from the Calhoun coal bed (Missourian) of the Illinois Basin (USA) are used to interpret spatial and temporal changes in plant communities in the paleo-peat swamp. Coal-ball and miospore floras from the Calhoun coal bed are dominated strongly by tree ferns, and pteridosperms and sigillarian lycopsids are subdominant, depending on geographic location within the coal bed. Although the overall composition of Calhoun peat-swamp assemblages is consistent both temporally and spatially, site-to-site differences and short-term shifts in species dominance indicate local topographic and hydrologic control on species composition within the broader context of the swamp. Statistical comparison of the Calhoun miospore assemblages with those from other Late Pennsylvanian coal beds suggests that the same basic species pool was represented in each peat-swamp landscape and that the relative patterns of dominance and diversity were persistent from site to site. Therefore, it appears that the relative patterns of proportional dominance stayed roughly the same from one coal bed to the next during Late Pennsylvanian glacially-driven climatic oscillations.

Several isolated marattialean synangia and sporangia are reported from coal balls collected from Coal Seam No.1 (C605) in the uppermost Permian Wangjiazhai Formation in Guizhou Province, south-western China. The synangia are radially symmetrical with diameters between 0.8 and 1.2 mm and are 1.7 mm long, consisting of 3–4 elongate sporangia that are fused basally, free distally and possess a pointed apex. The outer-facing sporangial wall is 4–5 cells thick and conspicuously differentiated. Spores are trilete, have a granular ornamentation and are nearly round equatorially with a diameter of 55–60 µm. Comparisons with other anatomically preserved Palaeozoic marattialean synangia from the Euramerican and Cathaysian floras permit their assignment to the genus of Scolecopteris (Zenker) Millay. In this species the thick, outer-facing sporangial walls and large trilete spores are features consistent with those of the Oliveri Group within Scolecopteris, a group that has previously been considered primitive within this genus. Distinctions from all other previously recognized species within the Oliveri Group lead to the creation of a new species, S. guizhouensis sp. nov. This species is the youngest of the reported species of Scolecopteris recognized from the Euramerican and Cathaysian floras, and provides important evidence on the organization of marattialean ferns from the Upper Permian strata of south China. © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society, 2006, 151, 279–288.

A new whole plant species of cordaitalean coniferophyte is reconstructed from a single Early Permian coal‐ball assemblage in northern China and is named Shanxioxylon sinense after its distinctive stem. This assemblage contains three cordaitalean whole plants reconstructed from evidence, including organs found in organic connection and other examples where two or more organs share distinctive anatomical features. With the exception of the fertile shoot systems, organs of the S. sinense plant may be ascribed to existing cordaitalean morphogenera, although in each case they represent distinct morphospecies. Stems have a septate central pith and have previously been assigned to S. sinense. Primary vascular architecture is sympodial, and primary xylem maturation of the cauline bundles is endarch. Adventitious roots are infrequently observed on smaller stems. Leaf traces are mesarch, diverging from the pith margin as a single bundle and approaching 8/21 phyllotaxis. Leaves are small and needle‐like. Roots are p...

Three new species of the lepidodendralean leaf genus Lepidophylloides are described and diagnosed from Early Permian coal ball assemblages in the Taiyuan Formation of northern China. In each case these species are distinct from other species of Lepidophylloides previously recognized from the Euramerican flora. Lepidophylloides hippocrepicus sp. nov. is characterized by leaves with a lateral stomatiferous region instead of the more conventional stomatiferous furrows observed in the genus, and also possesses a horseshoe-shaped vascular bundle sheath. Lepidophylloides taiyuanensis sp. nov. possesses leaves that are nearly triangular at the distal part and rhomboidal in the proximal part, and its leaves also have a xylem strand that changes from small and slightly horizontally elongated distally to large and triangular or crescent-shaped with its upper side concave at the proximal part while the lower part of the vascular bundle sheath extends into a U-shape. Lepidophylloides sclereticum sp. nov. has a vascular bundle sheath consisting of transfusion tracheids and a curved xylem strand with its upper side convex, and also possesses a mass of thick-walled fibrous cells with a hollow central part beneath the xylem strand. This new evidence suggests that the leaves of some species of Lepidophylloides from the Cathaysian flora are characterized by large and curved xylem strands in comparison to their Euramerican relatives, and that these leaves probably belonged to a morphologically and anatomically distinct group of lepidodendralean plants that thrived in Permian wetland ecosystems of the Cathaysian flora.

A distinctive kind of anatomically preserved cardiocarpalean ovule is described from the Early Permian Taiyuan Formation of northern China. Ovules are small, have 180° rotational symmetry, and possess variably thick integuments with prominent secretory cavities that may be empty, filled with resinous materials and in several instances appear to contain animal coprolites. Comparisons show that (where known) these features conform to those of Callospermarion undulatum (Neely) Rothwell, to which they are assigned, previously only known from the Pennsylvanian of Euramerica. These fossils represent the first indisputable occurrence of the genus Callospermarion in the Early Permian Cathaysian floras, and show the presence of callistophytalean seed-ferns in this palaeofloristic realm for the first time. These data combined with results from previous investigations now support the Early Permian northern Cathaysian flora including the Taiyuan Formation having evolved from the Late Carboniferous and earliest Permian Euramerican flora, with which it shares far too many generic level similarities for these co-occurrences to be coincidental. Our hypothesis is therefore that the Early Permian flora of the northern Cathaysian realm represents the continued evolution of wetland Euramerican-type coal-swamp floras, and as such is likely to present a model for evolutionarily driven floral change as opposed to the climatically driven floral changes observed in the Euramerican flora after the demise of coal-swamp environments. The distribution of coprolites in and immediately around glandular cavities in this species suggests specialised syndromes of herbivory existed in Early Permian Cathaysian ecosystems, with herbivores preferentially selecting these areas of the ovule integument.

Coal balls were collected from four coal beds in the southeastern part of the Illinois Basin. Collections were made from the Springfield, Herrin, and Baker coals in western Kentucky, and from the Danville Coal in southwestern Indiana. These four coal beds are among the principal mineable coals of the Illinois Basin and belong to the Carbondale and Shelburn Formations of late Middle Pennsylvanian age. Vegetational composition was analyzed quantitatively. Coal-ball samples from the Springfield, Herrin, and Baker are dominated by the lycopsid tree Lepidophloios, with lesser numbers of Psaronius tree ferns, medullosan pteridosperms, and the lycopsid trees Synchysidendron and Diaphorodendron. This vegetation is similar to that found in the Springfield and Herrin coals elsewhere in the Illinois Basin, as reported in previous studies. The Danville coal sample, which is considerably smaller than the others, is dominated by Psaronius with the lycopsids Sigillaria and Synchysidendron as subdominants. Coal balls from the Springfield coal were collected in zones directly from the coal bed and their zone-by-zone composition indicates three to four distinct plant assemblages. The other coals were analyzed as whole-seam random samples, averaging the landscape composition of the parent mire environments. This analysis indicates that these coals, separated from each other by marine and terrestrial-clastic deposits, have essentially the same floristic composition and, thus, appear to represent a common species pool that persisted throughout the late Middle Pennsylvanian, despite changes in baselevel and climate attendant the glacial–interglacial cyclicity of the Pennsylvanian ice age. Patterns of species abundance and diversity are much the same for the Springfield, Herrin, and Baker, although each coal, both in the local area sampled, and regionally, has its own paleobotanical peculiarities. Despite minor differences, these coals indicate a high degree of recurrence of assemblage and landscape organization. The Danville departs dramatically from the dominance–diversity composition of the older coals, presaging patterns of tree–fern and Sigillaria dominance of Late Pennsylvanian coals of the eastern United States, but, nonetheless, built on a species pool shared with the older coals.

International audience; Well-preserved specimens of Stauropteris oldhamia are described. The material was collected in the early 1920s from the Lower Westphalian (Early Pennsylvanian) Saurue seam from Belgium. The fossil plants occur as permineralized axes fragments within a coal ball. This study confirms most of the interpretations made by previous researchers. The observation of immature axis however suggests a less regular organization than previously interpreted beyond the three first branching orders. We also highlight the presence of profusely and dichotomously branched aphlebiae, the lack of laminate organs as well as the presence of hypodermal aerenchyma in all plant parts. We interpret these features as part of a very specialized assimilatory apparatus indicating an adaptation to a humid swamp environment.

Large areas of concentrated coal balls (permineralized peat) up to 4 m thick obstructed longwall mining in the Herrin Coal at the Old Ben No. 24 mine. The largest coal‐ball area mapped contained >1500 m 3 ; several areas contained >400 m 3 of coal balls. In‐mine mapping established that there were two types of roof (freshwater and marine), and that the coal balls were spatially correlated with the marine roof units. Regional studies and local data revealed that the younger, freshwater Energy Shale (mud) originally covered all of the peat deposited at the mine, but the mud was locally removed during a period of erosion. The great majority of coal balls are found within the coal seam, where they were permineralized in situ by carbonates. Some coal balls are found exposed on the eroded coal surface and others are within the channel fill associated with the erosion, which predates any marine sedimentation. Thus, the mineralization of the coal balls was synchronous with the erosion of the Energy Shale mud. Data from C‐and O‐isotope, geochemical, and mineralogical analyses of coal balls and associated materials were used to refine a depositional model of coal‐ball formation. The concentrated coal‐ball areas were created by the triggered degassing of CO 2 from partially decomposed peat in the presence of cations from fresh waters; 13 C/ 12 C ratios in these coal balls average −23.9‰. 13 C/ 12 C ratios as low as −34‰ occurring in the most concentrated coal balls are consistent with CO 2 produced by anaerobic oxidation of methane. Top‐of‐seam coal balls were formed later and show slight to strong marine influence; their 13 C/ 12 C ratios average −10.8‰.

Petrographic changes during coalification of three peat samples were investigated by artificial coalification experiments using a semi-open reactor system. Compressions of from 83 to 88% produced dark brown to black, shiny, flattened pellets exhibiting microscopic banding. Overall amounts of compression inversely correlated with the framework to matrix ratios ( F M ); although, certain tissue fragments remained relatively uncompressed due to the presence of tanniniferous cell fillings and also, hypothetically, to the presence of colorless plant secretions or gelified wall materials that were present in the cells but only recognizable after a change in color during coalification. The most distinct microscopic banding (longest and widest bands) developed in samples of the dome-formed peat facies, which had the highest framework to matrix ratios of any type and the greatest contents of surface litter composing the framework (i.e. highest S N ratio). The planar, root-dominated, Rhizophora facies showed the greatest change in microbanding character during coalification; in that, the numerous lens-like bands produced by the compressed roots were very distinct at the 60°/2100 psi (121.4 kg/cm2) stage but nearly disappeared at the 175°/5000 psi (289.1 kg/cm2)) stage. This is explained as a result of differences in rates of coalification of the different telinitic precursors in the roots (multilinear vitrinization) and could explain why roots are significant components of many modern peats (and ancient coal ball concretions) but are difficult to recognize in bituminous coals. Similarly, separation of cuticles from leaves in modern peat-forming environments, due to irreversible shriveling and subsequent enhanced microbiological decay, partially explains why leaf remains are also difficult to recognize in most coals, even those with abundant cutinites. Microcracks developed in all pellets, with dominant orientations of cracks being either perpendicular to induced banding or horizontal to it. Minute, vertical microcracks (interpreted as ‘dewatering’ features) were observed primarily in gelinitic bands, especially in the most fire-prone, Cladium coal facies; but, these rarely extended into juxtaposed microlithotypes as did most of the larger vertical cracks. Horizontal cracks tended to form at microband boundaries. Almost all humotelinitic and humocollinitic precursors showed some changes in color during artificial coalification, with humotelinites exhibiting less or slower changes than humocolinites or humodetrinites (finer-grained matrix material). Additionally, nearly all dark brown, degraded tissues in the peats became dark orange or red during coalification; but, many of these tissue masses were observed to contain significant amounts of minute inertinite derived from microorganisms (‘pseudomicrinite’) that only became prominent after coalification and subsequent change in color of surrounding macerals. Fusinite precursors were only found in the fire-prone Cladium facies; and, although, the coalified, doming-generated, Cyrilla facies exhibited evidence of significant drying events (i.e. occasional bands or parts of bands containing significant pseudomicrinites, macrinites and sclerotinites), it was dominated by huminitic (vitrinitic) components. Liptinites were most common in the coalified, dome-formed, Cyrilla facies and displayed a slight qualitative increase in red/green fluorescence during coalification and some possible flow of components into nearby cracks. Changes in mean random reflectance of huminitic macerals, although still requiring more data and only measured to the 60°C/2100 psi (121.4 kg/cm2) level, indicated increasing directions of change during artificial coalification, with humocollinitic macerals progressing from an average of about 0.21% to 0.32% and humotelinitic macerals (which consistently had lower inherent reflectances in the peats) progressing from 0.15 to 0.25%. The above petrographic results, along with previously reported chemical results, all suggest that the methods that we have used in these experiments have produced changes that might reasonably be expected to occur during natural coalification (despite the fact that we have speeded up the process). Although more work needs to be done to verify and refine these results and to establish a correlation between these artificial ‘coalification steps’ and true coalification, the new observations and conclusions from these studies might still be helpful in constructing models to predict or interpret coal seam characteristics and to establish the timing and release-potential of gaseous or liquid hydrocarbons from coals.

A review of coal-ball floras from Central and Western Europe is presented with special attention to recent studies of coal balls from England and Spain. Emphasis is placed on the stratigraphic and geographic distribution of taxa, and on a comparison of twelve floras including those of the Late Carboniferous “Great Coal Ball Horizon”, as well as two of Namurian age from the Czech Republic and Germany, and one new flora from Spain. The three richest floras include those from the Upper Foot and Union seams (Lancashire, UK) and Bouxharmont (Belgium). These differ in taxonomic diversity, relative to the number of species of gymnosperms, lycopsids and ferns. Patterns of occurrences of taxa for each major group of plants are discussed and compared with quantitative data provided recently for some floras by T.L. Phillips and colleagues. The significance of common versus rare taxa is discussed, and a list of species is proposed as most representative of Westphalian European coal-swamp associations. Comparison of the very different temporal ranges of about 40 important genera suggest that, since the Mississippian, there existed a sequential introduction from non-swamp habitats of plants that became abundant/dominant in later Euramerican coal swamps.

Coal balls in the Canadian Carboniferous System are known from the Clifton Formation (late Bolsovian) of New Brunswick and from the Foord seam (Stellarton Formation, late Bolsovian) of the Stellarton Basin of Nova Scotia. Coal balls from these two units are dominated by arborescent lycopods but ferns, seed ferns, calamiteans, and cordaiteans also occur. Baxter's list (Baxter, 1960) of coal-ball plants from New Brunswick is updated and these fossil plants are illustrated here for the first time on the basis of an examination of his peels. The palynomorphs and coal-ball plants of the Foord seam of the Stellarton Basin are illustrated and their paleoecology is discussed. Five genera of arborescent lycopods were present in the Foord swamp: Diaphorodendron, Paralycopodites, Lepidophloios, Sigillaria and Lepidodendron. The first three genera are represented in coal balls; the second two are also represented as compressions in the Foord seam; and all genera are represented in the spore assemblages from the Foord seam. The palynostratigraphy indicates that Sigillaria and Diaphorodendron were almost exclusively confined to the upper bench, whereas the other three genera were probably present in the Foord mire throughout its entire history. Palynomorphic changes in the Foord mire probably reflect gradual changes in wet and dry conditions.

Coal balls are formed from the precipitation of carbonate minerals, predominantly calcite, from water during or immediately post-peat formation. Previous petrological studies suggest permineralization occurred at various stages during the peatification process by precipitation from a mixture of marine and meteoric freshwater. The geochemical studies reported here aimed to test previous theories of coal ball formation. Coal balls studied here are from Upper Carboniferous and Carboniferous/Permian coal seams in Britain, United States of America, Belgium and China. Stable carbon isotopic values of calcites range from δ13C of −5 to −35‰ indicating highly variable contribution of decayed organic matter to the carbonate cement. Oxygen isotopic values of δ18O range from −3 to −15‰ suggest both marine and meteoric freshwater sources. The range, in the British coal balls in particular, with δ13C ranging from −7 to −25‰ indicates the complexity of carbonate generation. Isotopic data support at least four theories of carbonate coal ball formation. This makes their absence from post-Permian coals the more puzzling and it is suggested that the overall structure of the peat may play a role.

Carbonate concretionary bodies were encountered during mining of the Beulah-Zap lignite seam in the Coteau Properties' Freedom mine, Mercer County, North Dakota. Preliminary studies show that areal and vertical distribution of the concretions are variable. All concretions examined are composed almost entirely of calcite. They occur as thin tabular bodies, as more or less elliptical forms, or as tear shaped bodies, and may occur individually or as clusters of buff-colored, poorly consolidated to solidly crystalline material. The carbonate masses vary in size from a few millimeters to tens of centimeters. Bedding in the lignite may display some compactional folding over dense spheroidal to elliptical concretions, indicating formation of the concretions prior to compaction. Internal morphology of the concretions is complex, and includes cone-in-cone structure, cross-cutting calcite veinlets, and multiple generations of calcite. Carbon isotope values suggest the concretions are composed of biogenic carbonate, probably related to early diagenesis and decomposition of organic matter (peat); oxygen isotope values are light, and consistent with a freshwater origin.