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Coal balls, in which fossil plants are preserved in permineralized peat deposits, have widely been described from coal deposits representing the tropical forest of the Carboniferous. Coal ball preparation techniques have evolved over the past century, with the cellulose acetate peel method becoming the standard in the 1950s. While coal ball research is not as active as it has been in the past, large collections of coal balls and their respective peels still form a large part of many museum and university collections. This contribution aims to review coal ball preparation methods, curation, and the digital archiving of peels to create a cohesive guide for researchers working with coal balls and other petrified plant material. The physical and digital curation of cellulose acetate peels and other types of coal ball specimens is critical for long‐term preservation and accessibility. Physical curation involves embedding coal balls in media to slow pyrite deterioration. Digital curation creates high‐resolution scans of peels, which can be shared and accessed online. Cellulose acetate peels and their digital curation are a valuable and accessible technique for the analysis of coal balls, and physical and digital curation ensures long‐term preservation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Permineralization offers exceptional structural preservation to the level of cellular components, many of which are found within fossilized plant specimens. In some cases, structures within plant cells, particularly those found within spores and pollen grains, have been interpreted as nuclei. Although these structures have been studied morphologically and ultrastructurally, little is known about their composition and origin. This study uses petrographic thin sections and ultraviolet (UV) Raman spectroscopy to reexamine cellular inclusions within three types of Pennsylvanian spores and pollen grains with the intent to interpret the molecular composition and therefore, the identity of these structures. Thin sections are examined using Raman spectroscopy, which indicates the presence of disordered carbonaceous material and calcite. There is no significant difference in the chemical composition between the intracellular inclusions and surrounding areas within each specimen. This study represents one of the first applications of Raman spectroscopy in which the internal cell contents of fossil plant taxa are analyzed. Results do not support the presence of nuclei, although further examination is recommended to elucidate the origin and identity of the intracellular inclusions. [ABSTRACT FROM AUTHOR]

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 complexes 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. [ABSTRACT FROM AUTHOR]

Lepidodendralean lycopsids, a dominant component in Late Palaeozoic wetland plant communities, possess a diversity of reproductive structures that are primarily known from the Late Palaeozoic floras of Europe and North America. Here we document an anatomically preserved lepidodendralean lycopsid sporophyll with attached megasporangium from the Lower Permian Taiyuan Formation in Shanxi Province, northern China. The sporophyll has a pedicel onto which the sporangium is attached, and the sporangium is dorsiventrally flattened, proximally dehiscent and longitudinal ridged. The megasporangial wall comprises three zones: an outer uniseriate layer of columnar cells, a middle layer 1–3 cells thick comprising isodiametric parenchymatous cells, and an inner zone 1–3 cells thick of thick-walled cells. The vascular system comprises a single xylem strand surrounded by zone of parenchyma that continues through the pedicel into the lamina. Within the megasporangium a single functional megaspore and three abortive megaspores occur. Features of this specimen conform to Achlamydocarpon Schumacher-Lambry, and comparisons with other species show it shares similarities with A. takhtajanii (Sni.) Schumacher-Lambry and A. varius Taylor and Brack-Hanes. Although the morphology and anatomy of the specimen we describe overlaps with these two species, it is distinct from both leading to the erection of the new species A. intermedium sp. nov. The evolutionary significance of A. intermedium sp. nov. and the identity of its parent plant are considered, and the status and systematic position of “Oriental lepidophytes” from the Cathaysian floras are discussed. [ABSTRACT FROM AUTHOR]

A new kind of marattialean raches are reported from the coal balls in Coal Seam No.7 in the upper part of the Taiyuan Formation (early Early Permian) from Taiyuan, Shanxi, China and are assigned to the genus Stipitopteris Grand'Eury (Psaroniaceae). The present specimens are different from all six reported species of the genus, and are therefore proposed as a new species: Stipitopteris shanxiensis. The raches of the new species are generally dorsi-ventrally flattened. The main raches usually exhibit scales of different forms on their surface. Beneath the epidermis is a zone of parenchymatous cells, some of which contain tannin-like contents. Inside this is a zone of small sclerenchymatous cells. Inward are the ground tissue and vascular bundles. The vascular bundles are continuous and are in two circles: the outer circle assumes a transversely elliptical shape with the gap and pinna trace, and the inner circle assumes a shallow C-shape with inrolled ends. The ground tissue located at the inner side of the vascular bundle is composed of thicker-walled parenchymatous cells. The cells of the ground tissue are vertically elongated in longitudinal sections. Subordered raches are smaller and have simpler structures than the main raches. The parenchyma zone beneath the epidermis is thinner, usually one to two cells wide and the sclerenchyma zone is usually absent. The scales are poorly developed and there is only one C-shaped vascular bundle. The new species is comparable to the crosiers of Psaroniaceae of the Euramerican Flora in some aspects, for example, it has a dorsi-ventrally flattened rachis and scales on the surface of the rachis. However, the other features and the preservative conditions of the present specimens indicate that they are not crosiers, but fully developed or mature raches. The new species is the first well-studied anatomically-preserved rachis of Psaroniaceae from the Cathaysian Flora and bears significance not only in understanding the anatomy and taxonomy of Psaroniaceae in the Cathaysian Flora, but also in the relationship between the Euramerican Flora and the Cathaysian Flora. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [Copyright &y& Elsevier]

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. [Copyright &y& Elsevier]

Coal balls are calcareous peats with cellular permineralization invaluable for understanding the anatomy of Pennsylvanian and Permian fossil plants. Two distinct kinds of coal balls are here recognized in both Holocene and Pennsylvanian calcareous Histosols. Respirogenic calcite coal balls have arrays of calcite δ18O and δ13C like those of desert soil calcic horizons reflecting isotopic composition of CO 2 gas from an aerobic microbiome. Methanogenic calcite coal balls in contrast have invariant δ18O for a range of δ13C, and formed with anaerobic microbiomes in soil solutions with bicarbonate formed by methane oxidation and sugar fermentation. Respirogenic coal balls are described from Holocene peats in Eight Mile Creek South Australia, and noted from Carboniferous coals near Penistone, Yorkshire. Methanogenic coal balls are described from Carboniferous coals at Berryville (Illinois) and Steubenville (Ohio), Paleocene lignites of Sutton (Alaska), Eocene lignites of Axel Heiberg Island (Nunavut), Pleistocene peats of Konya (Turkey), and Holocene peats of Gramigne di Bando (Italy). Soils and paleosols with coal balls are neither common nor extinct, but were formed by two distinct soil microbiomes. Unlabelled Image • Coal balls were calcareous Histosols (peats), currently rare, and of two microbiome types. • Holocene calcareous peats in Eight Mile Creek, South Australia, were aerobic respirogenic. • Respirogenic coal balls have correlated calcite δ18O and δ13C like those of desert soils. • Holocene peats of Gramigne di Bando, Italy, were anaerobic methanogenic. • Methanogenic calcite coal balls have invariant δ18O for a range of δ13C from methanogens. • Respirogenic and methanogenic coal balls are known from the Carboniferous and other ages. [ABSTRACT FROM AUTHOR]