Medullosan Pteridosperms Research Articles

Kasimovian floristic change in tropical wetlands and the Middle–Late Pennsylvanian Boundary Event

Abstract A threshold-like vegetational change in tropical wetlands occurred in the early Kasimovian (the US Desmoinesian–Missourian boundary) – Event 3. Two earlier significant changes occurred, first in the mid-Moscovian (Atokan–Desmoinesian; ∼Bolsovian–Asturian) – Event 1, and the second in the late Moscovian (mid-Desmoinesian; mid-Asturian) – Event 2. These changes occurred during a time period of dynamic and complex physical change in Euramerican Pangaea driven by changes in polar ice volume and accompanying changes in sea level, atmospheric circulation, rainfall, and temperature. During the Event 3 change, hyperbolized as ‘the Carboniferous rainforest collapse’, lycopsid dominance of (mostly peat) swamps changed to marattialean tree-fern and medullosan pteridosperm dominance, and biodiversity decreased. Event 3 encompassed one glacial–interglacial cycle and included vegetational turnover in other wetland habitats. For several subsequent glacial–interglacial cycles peatland dominance varied, known from palynology, before stabilizing. These vegetational changes likely reflect climatic events driving unidirectional, non-reversible wetland vegetational changes, during cooler, wetter parts of glacial–interglacial cycles. Discussion is complicated by different placements of crucial stratigraphic boundaries, but under the same names, compromising both clear communication and understanding of the literature. Not the least is the floating base of the Cantabrian Substage, together with the position of the Westphalian–Stephanian Stage boundary.

Dominance-diversity architecture of a mixed hygromorphic-to-xeromorphic flora from a botanically rich locality in western equatorial Pangea (lower Permian Emily Irish site, Texas, USA

Here we describe the Leonardian-age flora from “Emily Irish” (Russell Ranch), a small oxbow lake deposit, which is believed to be one of the most extensively collected, single-excavation floras of this age from any place in the world, including ca. 5200 hand specimens housed at the US National Museum of Natural History. The flora is dominated by a mixture of xeromorphic and meso-hygromorphic elements. The xeromorphs include conifers, taeniopterids, cordaitaleans, and noeggerathialeans. The mesomorphic-to-hygromorphic elements include marattialean tree ferns, sphenopsids, lycopsids, callipterids, and medullosan pteridosperms. This co-dominance of hygromorphic and xeromorphic elements is made especially conspicuous by the intimate co-mingling of plant remains from each group on the same hand specimens, and by the relative preservation-state of the macrofossils, which does not differ between the two groups. These observations suggest that they inhabited the same landscape immediately surrounding the depositional environment, and were likely only differentiated by microhabitat. We suggest that the Emily Irish flora grew under seasonally dry climate, but that areas adjacent to the lake and feeder streams retained sufficient moisture to support patches of taxa requiring consistently high soil moisture. These patches, thus, were embedded within a landscape of periodic moisture deficit that supported vegetation composed mostly of xeromorphic elements. This is more likely than requiring the xeromorphic taxa to be transported to the site from extrabasinal habitats, the nearest of which were hundreds of kilometers away at the time the deposit formed.

The earliest evidence of cordaitalean cuticles from coal in the Pennsylvanian of Europe (Langsettian, Upper Silesian Basin, Czech Republic)

A dispersed cuticular assemblage with Cordaites Unger represents the oldest record of cordaitalean remains in peat deposits. Cordaitalean cuticles are easily distinguished by their elongated tetragonal or oblong cells and typical stomatal complexes. This assemblage comes from the coal seam 26 of the Karviná Formation, Lower Suchá Member, a few meters above the Namurian/Westphalian boundary in the Upper Silesian Basin. Cordaitaleans represent 23% of the cuticular assemblage, and consist of two species of abaxial cuticles (Cordaabaxicutis cf. jaworznoensis Šimůnek and Florjan and C. jacobii Šimůnek sp. nov.) and four species of adaxial cuticles (Cordaadaxicutis jaroslavii Šimůnek sp. nov., C. orlovensis Šimůnek sp. nov., C. doubravensis Šimůnek sp. nov. and C. detmarovicensis Šimůnek sp. nov.)Cordaabaxicutis cf. jaworznoensis has stomata arranged in stomatiferous bands in irregular rows. The Polish Cordaabaxicutis jaworznoensis has regular stomatal rows. It is highly probable that Cordaabaxicutis cf. jaworznoensis is conspecific with Cordaites karvinensis Šimůnek and C. sustae Šimůnek. All these species have small papillae on the abaxial cuticle, which is typical for peat-swamp species. Cordaabaxicutis jacobii has stomata arranged in stomatal rows, however, another sample of this species tends to have them in multiple rows. The structure of the stomatal complex is similar to Cordaabaxicutis laziskae Šimůnek and Florjan, but the subsidiary cells are much smaller.Cordaadaxicutis jaroslavii has stomata arranged in sparse rows, whereas the other Cordaadaxicutis new species have very low stomatal densities and stomatal complexes irregularly dispersed on the epidermis. Cordaadaxicutis jaroslavii has slightly cutinised lateral subsidiary cells of stomata, C. orlovensis has prominent guard cells and similar lateral subsidiary and ordinary cells. Central parts of periclinal cell walls of C. doubravensis are thinner.The most common species in the dispersed cuticular assemblage are Cordaabaxicutis cf. jaworznoensis and Cordaadaxicutis jaroslavii. This cordaitalean assemblage represents at least four biological species. The rest of the dispersed cuticular assemblage is represented by lyginopterid and medullosan pteridosperms, cuticles of seed integuments and rachides.

Species of the medullosan ovule Stephanospermum from the Lopingian (late Permian) floras of China

The medullosan pteridosperm ovule Stephanospermum Brongniart is a well-known component of Carboniferous aged coal-ball and siderite nodule floras from North America and Europe but also occurs in the Permian floras of Cathaysia where it is represented by the Lopingian (late Permian) aged species Stephanospermum trunctatum (Li) Wang et al. (2009) from coal-balls in the Wangjiazhai Formation in Southern China. We provide a detailed emendation of S. trunctatum and illustrate it comprehensively for the first time, and document an additional specimen from the Wangjiazhai Formation coal-ball assemblage that we assign to Stephanospermum shuichengensis sp. nov. S. shuichengensis is distinguished from S. trunctatum by the absence of apical teeth in the sclerotesta and non-obovate base. The two species of Stephanospermum from the Wangjiazhai Formation are important as they extend the stratigraphic and geographical range of the genus from the Pennsylvanian of Euramerica into the Lopingian of Southern China, and demonstrate that the genus persisted in wetland, peat forming environments in the run up to the end-Permian mass extinction event. The 44 MY stratigraphic discontinuity between the Euramerican and the Cathaysian species, here named the Stephanospermum gap, leads us to infer that the genus was likely to have occurred in the Pennsylvanian–Permian successions of southern Russia and northern China that are geographically and stratigraphically intermediate to the known occurrences but from which the genus has yet to be discovered. Medullosan pteridosperms appear to have become extinct at or immediately prior to the Permian–Triassic boundary that coincides with the Permo–Trias mass extinction event; although the exact causes of this loss in plant diversity remains unknown, a response to regional climatic drying is likely to have been a contributing factor.

The “seeds” onPadgettia readiare insect galls: reassignment of the plant toOdontopteris, the gall toOvofoligallitesn. gen., and the evolutionary implications thereof

The Early Permian (Asselian) Euramerican plantPadgettia readiMamay is reassigned toOdontopterisBrongniart, asO. readi(Mamay) Stull et al. n. comb. Distinctive elongate structures on neuropteroid pinnules of this plant, previously interpreted as fructifications, are herein reinterpreted as foliar histoid galls, structurally analogous to blister or vein galls, and probably induced by an early lineage of hemipterans or mites. These distinctive features are assigned to the new gall ichnogenusOvofoligallitesLabandeira, n. ichnogen. n. ichnosp, asO. padgettiLabandeira. The Early Permian association between anOdontopterishost andOvofoligallitesgallers probably originated during the Middle Pennsylvanian as a similar, antecedent association betweenMacroneuropteris scheuchzeri(Hoffmann) Cleal, Shute, and Zodrow and the maker of U-shaped surface features long known as a distinctive, unattributed damage type, but now recognizable as a likely gall. The persistence of this association between the galler and certain medullosan pteridosperms into the Permian adds to the morphological richness of the Permian galler insect fauna. The Permian ecological expansion of galling insects resulted in colonization of new host plants, primarily through a shift from the consumption of entire, mostly pteridophyte axial organs during the Pennsylvanian to the partitioning of seed plant tissues in leaves and small branches in the Permian. TheOvofoligallitesgaller was part of a diverse Permian galler guild involving a variety of plant taxa, organs and tissues that overwhelmingly targeted multiple lineages of seed plants.

Palaeoecology of Macroneuropteris scheuchzeri, and its implications for resolving the paradox of ‘xeromorphic’ plants in Pennsylvanian wetlands

The medullosan pteridosperm Macroneuropteris scheuchzeri (Hoffmann) Cleal, Shute & Zodrow was widespread and abundant in the Middle to Late Pennsylvanian forests of tropical Pangaea. On the basis of its thick cuticles, few adaxial stomata, sunken stomata, and dense trichomes, it has been inferred to be a xeromorphic plant. Here we test that hypothesis by analyzing its facies distribution, especially in relation to coals, at 273 site collections from ~45 stratigraphic horizons accessioned in the Smithsonian National Museum of Natural History, Washington, D.C., U.S.A. The collections represent mostly (par)autochthonous assemblages and cover the taxon's complete known temporal range west of the Appalachians in west-central Pangaea. Chi-square analysis of facies-occurrence data indicates that M. scheuchzeri had a strong preference for mineral-enriched wetlands that immediately preceded and followed the development of peat swamps and mires (coals), particularly during the late Middle Pennsylvanian (late Moscovian) times, coincident with a period of reduced polar ice volume. In the Late Pennsylvanian, following an interval of global warming and tropical wetland reorganization, palaeoequatorial climate shifted to an overall drier mode. This was accompanied by the disappearance of M. scheuchzeri from Europe and its limitation, west of the Appalachians, to the wettest available habitats on the landscape. Thus, our data falsify the hypothesis that M. scheuchzeri was a conventional xerophyte, but highlight the paradox of a plant with apparent xeromorphic features confined to a wetland habitat. We consider several possible explanations for this association: (1) response to nutrient deficiency, (2) response to substrate salinity (due to growth in coastal mangrove habitats), (3) response to the composition of the Palaeozoic atmosphere, (4) return on investment (long leaf lifespan), and (5) phylogenetic constraint reflecting ancestral conditions. Our findings have broader implications for interpreting a wide variety of other Pennsylvanian wetland plants, which similarly show ‘xermorphic’ features.

Dryland plant communities in the Pennsylvanian (mid- to late Bolsovian) Winterbourne Formation of Bristol, southern Britain: Further evidence for taphonomic megabias

Pennsylvanian dryland plant communities are poorly known compared to those of coeval wetlands – a function of taphonomic megabias. Here we describe a new example from the mid- to late Bolsovian Winterbourne Formation of Staplehill, Bristol, southern Britain based on a re-examination of historical fossil material. These fossils, collected by Herbert Bolton in 1905/6, initially studied by Dennis Lillie in 1908/9, and later re-assessed by Robert Crookall in 1926/7, were thought to have been lost until their recent discovery in an unaccessioned repository at the British Geological Survey. The calcified assemblage, which we describe and fully illustrate for the first time, is dominated by cordaitalean remains ( Dadoxylon trunks, Amyelon roots and Mesoxylon aerial axes), together with a single medullosan pteridosperm ( Sutcliffia lillieii) and an indeterminate lycopsid (possibly sigillarian). Locality and facies data collected at the time of the original discovery, combined with new facies data from boreholes, limited outcrops, and sediments adhering to the fossils, demonstrate that this assemblage was deposited in a well-drained alluvial plain environment. Three independent lines of evidence indicate a seasonal subhumid tropical climate: (1) the breccia-conglomerate unit that hosts the fossil assemblage is interpreted as the deposits of a somewhat flashy alluvial drainage, (2) carbonate rhizoconcretions reworked into the conglomerate with the water-worn fossils are interpreted as remains of caliche paleosols that develop only under conditions of seasonal water deficit, and (3) erratic growth interruptions in the fossil woods indicate the plants grew under aperiodic water-stressed conditions. These findings provide further evidence that gymnosperm-dominated dryland ecosystems were more abundant and widespread in the Pennsylvanian tropics than previously recognized.

Resolving the systematic and phylogenetic position of isolated ovules: a case study on a new genus from the Permian of China

Isolated ovules occur in many fossil plant assemblages, where they provide important insights into seed-plant diversity and evolution. However, in many cases, the ovules cannot be attributed to individual groups of seed plants, restricting systematic and evolutionary assessments that can be made from otherwise well-characterized fossil taxa. In the present paper, we describe a new kind of ovule discovered in tuffaceous sediments from the Permian-aged Xuanwei Formation in Guizhou Province, China. This ovule has 180° rotational symmetry and an integument comprising a variably thick sarcotesta, a uniformly thick sclerotesta and a uniformly thin endotesta. The nucellus is attached to the integument at least basally and contains a collapsed seed megaspore; a nucellar apex is absent. Both the integument and nucellus are vascularized by paired bundles in the major plane of the ovule; the integumentary bundles are considerably larger than the nucellar bundles and the nucellar bundles emerge from a conical vascular pad. Generation of a three-dimensional reconstruction based on serial peels revealed the gross morphology and organization of the ovule and highlighted the presence of features consistent with cardiocarpalean-type ovules (ovule shape, histological features of the integument) and also features more typical of lagenostomalean- and trigonocarpalean-type ovules (large integumentary bundles, presence of nucellar bundles). To assess the affinity and evolutionary significance of the ovule, it has been included in a cladistic matrix of cardiocarpalean-, lagenostomalean- and trigonocarpalean-type ovules. Results place the ovule within the cardiocarpalean group of ovules known to have been produced by several plant groups, including cordaitean coniferophytes, pteridosperms and Palaeozoic conifers. The cladistic topology supports generic level distinction of the present species, requiring the establishment of Muricosperma guizhouensis Seyfullah & J.Hilton gen. & sp. nov. Lagenostomalean ovules produced by hydrasperman pteridosperms form a basal paraphyletic grade, whereas trigonocarpalean ovules produced by medullosan pteridosperms form a monophyletic group in which Stephanospermum is paraphyletic with respect to Rhynchosperma and Pachytesta. The results also place the Mississippian ovule Mitrospermum bulbosum apart from all of the Pennsylvanian species of Mitrospermum that form a strongly supported clade. Consequently, M. bulbosum is transferred to the new genus Whitaddera Seyfullah & J.Hilton as W. bulbosa (Long) Seyfullah & J.Hilton. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 164, 84–108.

COMPOSITION AND STRUCTURE OF AN IN SITU MIDDLE PENNSYLVANIAN PEAT-FORMING PLANT ASSEMBLAGE BURIED IN VOLCANIC ASH, RADNICE BASIN (CZECH REPUBLIC)

A three-dimensional reconstruction is provided of the composition, spatial distribution, and structure of a single-aged, Middle Pennsylvanian (Moscovian) peat-forming forest of a high-ash, planar (rheotrophic) mire, buried in situ by volcanic ash and preserved in the Lower Radnice Coal of the Radnice Basin (Czech Republic). The reconstruction is based on a detailed taxonomic and taphonomic analysis of fossils in a ∼0.5-m-thick tuff bed at the base of the Whetstone Horizon excavated over an area of 93.5 m 2 . In all, 24 whole-plant taxa of various growth forms were identified. This assemblage represents a lepidodendrid- and Cordaites borassifolius -dominated forest, with a well-developed understory of subarborescent lycopsids, tree ferns, medullosan pteridosperms, and calamites, as well as herbaceous ground cover. Lycopsids were dominated by Lepidodendron simile bearing Flemingites -type cones and L. lycopodioides ; Lepidophloios cf. acerosus was subdominant. Lianas, mostly lyginopterid pteridosperms and some ferns, were usually found close to upright stems. The ground cover, mostly ferns and sphenophyllaleans, was taxonomically the most diverse stratum, although only a minor contributor to the peat. Based on samples from the coal roof, the palynological record is in agreement with the tuff bed assemblage except for the quantity of certain taxa. To reduce this bias, compression R-values were calculated from the percent cover of aerial plant parts in the excavation and in the dispersed palynoflora. These R-values suggest that in the palynological record, arborescent lycopsids and sphenophylls are greatly overrepresented, ferns and cordaites strongly underrepresented, and calamites are almost the same in both records.

A Middle Pennsylvanian (Bolsovian) peat-forming forest preserved in situ in volcanic ash of the Whetstone Horizon in the Radnice Basin, Czech Republic

The precursory mire of the Middle Pennsylvanian (Bolsovian) Lower Radnice Coal was buried in situ by volcanic ash, preserving the taxonomic composition, spatial distribution, vertical stratification, and synecology of this peat-forming ecosystem in extraordinary detail. Plant fossil remains represent the pre-eruption vegetation of the swamp, which resulted from accumulation of peat in a high-ash, planar (rheotrophic) mire situated in a narrow palaeovalley containing an active fluvial system. A tuff bed (the Bělka) at the base of the volcaniclastic Whetstone Horizon was exposed in two contiguous excavations over an area of 50 m 2 in the Radnice Basin of western Bohemia, Czech Republic. Twenty-seven morphotaxa were identified, representing 20 whole-plant species with a wide variety of growth forms. The canopy of the peat-forming community was dominated by Cordaites borassifolius trees together with the arborescent lycopsid “ Lepidodendron” (= Paralycopodites), whereas Lepidophloios cf. acerosus was subdominant. Evidence suggests that the laterally extensive “crowns” of these arborescent lycopsids would have overlapped during the final phase of their life cycles, but differences in the height of tree species resulted in a complex and vertically variable canopy interrupted by randomly distributed gaps. The understorey was dominated by medullosan pteridosperms and marattialean tree ferns, whereas zygopterid ferns and sphenophylls comprised the bulk of the ground cover. In comparison with the canopy, understorey and ground cover species were less abundant and patchier in distribution, with almost complete absence beneath the deep shade of C. borassifolius trees. Lianas that entwined arborescent trees were an important component of the peat-forming forest. Three lyginopterid pteridosperm species along with a sphenophyll had a lianescent habit based on their close association with upright or prone lycopsid trunks and “canopy” branches. Species richness in the swamp superficially appears low. However, considering the small area of excavation, along with the higher diversity known from the same tuff bed in the adjacent, former opencast Ovčín Mine, it appears that species richness in the forest was comparable to some of the less diverse Westphalian peat-forming swamps in the U.S.A. The Lower Radnice mire vegetation was compositionally homogeneous, but had a heterogeneous distribution with patchiness occurring at a very fine scale. The preserved plant assemblage most resembles mires dominated by medullosan pteridosperms and Paralycopodites described from upper Westphalian coal balls in the U.S.A., which were characterised by high diversity in all storeys and involved plants centred in high-ash peat-forming swamps.

Re-evaluation of Halle’s fertile pteridosperms from the Permian floras of Shanxi Province, China

In 1927, T. G. Halle published an extensive synthesis of the Permian fossil plant assemblages from China’s Shanxi Province that included five genera and species of seed plant that either had ovules in organic attachment or closely and repeatedly associated with foliage. These fertile pteridosperms were the subject of a later publication (1929) that provided additional information on each species, but since that time only Nystroemia pectiniformis Halle has been subjected to detailed investigation based on the original materials. Reinvestigation of the remaining four species has yielded additional examples and new information for each species, and has confirmed the pteridospermalean affinity for three of the four species. Alethopteris norinii Halle shows organic attachment of a pollen organ similar to Wittleseya (Newberry) Halle and is reinterpreted as a microsporangiate medullosan pteridosperm. Emplectopteris triangularis Halle and Sphenopteris tenuis (Schenk) Halle both bear numerous ovules attached directly to the leaf laminae, with Emplectopteris conforming with the gross-organisation of callistophytalean pteridosperms and S. tenuis being interpreted as a derived lagenostomalean pteridosperm. However, discovery of the counterpart to the key specimen of Pecopteris wongii Halle that Halle interpreted as bearing ovules demonstrates this species to be a sterile marattialean frond that agrees with its assignment to Pecopteris. In addition, two further specimens are demonstrated to be fertile organs of previously unknown pteridosperms; Norinosperma shanxiensis gen. et sp. nov. bears cardiocarpalean ovules abaxially on the proximal portions of the frond with ovules positioned directly on the veins of a leaf lamina; Norinotheca shanxiensis gen. et sp. nov. bears large pollen organs abaxially and singly on the vein of the leaf lamina. Collectively Halle’s pteridosperms remain important today as they are some of the few specimens that actually demonstrate organic connection of fertile organs to foliage, helping to characterise the morphology and organisation of this seed plant group. These species also demonstrate the persistence of seed plant families and genera in the Permian of China that became regionally extinct at the end of the Carboniferous in Euramerica, and show that pteridosperms remained an important component of Permian as well as Carboniferous floras globally.

Plant taphonomy and palaeoecology of Stephanian limnic wetlands in the eastern Pyrenees (Catalonia, Spain)

Late Pennsylvanian (Stephanian C) limnic wetlands from the Surroca-Ogassa coalfield, (eastern Pyrenees, Catalonia, Spain) are characterised for the first time based on combined sedimentological, taphonomic, and palaeoecological analysis. Peat mires occurred in floodplain settings, and they were probably formed by monospecific stands of Sigillaria. These mires were swept away by pyroclastic flows, which produced the accumulation and orientation of sigillarian logs on the top of the volcanoclastic deposits. Floodplains were generally devoid of vegetation, with the exception of small sphenopsid stands. Calamites also grew within active fluvial channels. They were accompanied by marattialean tree ferns in low-regime fluvial channels. Medullosan pteridosperms bearing Alethopteris foliage and Pachytesta seeds were extremely abundant in particular horizons and grew probably in floodplain margins covering ancient peat mires. Parautochthonous cordaitalean remains were abundant in distal alluvial deposits.

Vegetation ecology of Early Pennsylvanian alluvial fan and piedmont environments in southern New Brunswick, Canada

The vegetation ecology of Pennsylvanian upland/dryland regions is poorly known, despite its evolutionary significance. Here, fossil plant assemblages are described from well-drained alluvial fan/piedmont deposits in the uppermost Boss Point and Tynemouth Creek formations (late Yeadonian–Langsettian), southern New Brunswick. Beds record the northward building of a large alluvial fan complex over alluvial plain deposits in response to near-continuous sourceland uplift. Proximal alluvial fan environments, characterized by sheetfloods and braided streams, were dominated by large cordaitalean trees, medullosan pteridosperms, ferns, and calamiteans. Distal alluvial fan environments, where braided stream and leveé/splay sedimentation predominated, were covered by similar vegetation, together with lycopsids in localized poorly drained depressions. Calamitean thickets were particularly widespread in rapidly aggrading settings on the distal fan. Well-drained alluvial plains beyond the fan toe were characterized by axial braided rivers containing cordaitalean trunks transported from proximal settings. Piedmont vegetation is otherwise poorly resolved. All studied plant assemblages are of low- to medium-diversity, and dominated by the remains of a single group, cordaitalean seed plants. Such dominance-diversity characteristics, together with the presence of charcoal, the product of wildfire, imply that Pennsylvanian upland/dryland vegetation experienced water-stress and that the seed habit was integral to successful colonization.

Place vs. time and vegetational persistence: a comparison of four tropical mires from the Illinois Basin during the height of the Pennsylvanian Ice Age

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.

Fire ecology of a Late Carboniferous floodplain, Joggins, Nova Scotia

The facies distribution and palaeobotanical identity of fossil charcoal is described from the Upper Carboniferous (Westphalian A–B) Joggins section, Nova Scotia, in order to examine the fire ecology of early Westphalian floodplains. Three charcoal assemblages are noted. Assemblage (1) consists of channel sandstone bodies, containing beds of calcrete breccia, cordaite logs (up to 3 m long), and coniferopsid wood charcoal. This assemblage records upland coniferopsid forest fires which altered basin hydrology and promoted flooding in downstream floodplain rivers. Assemblage (2) consists of thin (1–8 mm thick) coals containing hollow, sigillarian tree stumps and lepidodendrid and medullosan plant compressions. Fifteen of the 29 stumps observed have a 2–5 cm thick basal layer infilling the stumps, composed entirely of sigillarian charcoal. Sigillarian and medullosan charcoal is also scattered around the outside of these stumps. This assemblage represents fire in lowland peat-forming communities dominated by Sigillaria and medullosan pteridosperms. These forest fire profiles were slowly buried in floodplain muds. Assemblage (3) consists of a heterolithic sheet sandstone body containing a 2.5 m high sigillarian tree trunk with an internal, basal trunk deposit of sigillarian charcoal and a lightly charred bark rind. This also records fire in lowland sigillarian forests, but, in contrast to (2), this forest fire profile was buried rapidly in a distributary lobe.

A transect through a clastic-swamp to peat-swamp ecotone in the Springfield Coal, Middle Pennsylvanian age of Indiana, USA

Permineralized fossil plants in coal balls were collected along a kilometer transect through an organic-rich shale in the Springfield Coal in southwestern Indiana. The organic shale is an upper bench of the Springfield Coal in an area where the coal is split into an upper and lower bench by a complex system of clastics that originated as a splay. The clastic wedge, described as the Folsomville Member/Leslie Cemetery paleochannel, is up to 6 km wide and 15 m thick. The transect begins approximately 100 m from the edge of the clastic wedge that splits the coal seam and follows the upper bench of coal over and toward the center of the clastic wedge. The dominant elements of the vegetation were the lycopsid tree Paralycopodites brevifolius and several species of medullosan pteridosperms. This report confirms the ecotonal habitats of this vegetation.

Responses of Leaf Anatomy to Light Environment in the Tree Fern Cyathea caracasana (Cyatheaceae) and Its Application to Some Ancient Seed Ferns

The ecological interpretation of extinct plants requires that function-based ecological analogy be made between extant and extinct organisms. Particularly for non-angiosperms, such analogy has been reluctantly assumed. Using a nonangiosperm model, this study identifies a specific suite of characters that can be used to interpret light environments for ancient plants. The tree fern Cyathea caracasana is used as a living model because it offers structural and architectural analogy with ancient tree ferns and some Paleozoic free-standing arborescent pteridosperms. A variety of leaf anatomical and morphological measurements were made on 34 individuals growing in secondary forest and abandoned pasture at Reserva Natural La Planada, Nariho, Colombia. Leaf characters were correlated with sitelight conditions quantified from hemispherical photographs. Spearman correlation coefficients show that blade size, petiole length, and palisade/ spongy mesophyll ratio are well correlated with light environment. Significant relationships were also observed in frond surface area, thickness of ultimate segment, epidermis thickness, and hypodermis thickness. Although some features may be influenced by nutrient and water status, a well-developed palisade layer and thick hypodermis are specific indicators of light environment that vary plastically in Cyathea caracasana. These data can be used to refine ecological interpretations of extinct foliage; Alethopterisand Neuropteristype medullosan pteridosperms of the Middle Pennsylvanian (Westphalian) of Euramerica provide an illustrative example. INTRODUCTION

The chemical composition of Upper Carboniferous pteridosperm cuticles

Microscopically well-preserved leaf cuticles from four Upper Carboniferous pteridosperm (seed fern) genera have been analyzed using solid state 13C NMR and Curie-point pyrolysis. The chemical analyses reveal the presence of highly aliphatic macromolecules, comparable with cutan. Cutan production is considered to be responsible for the preservation of these plant structures, and hence for the abundance of well-preserved medullosan pteridosperm foliage in the Upper Carboniferous. Based on a comparison of data from the literature, and these new results, it is suggested that the resistant constituents of these cuticles may serve as an additional source of n-alkanes on diagenesis and catagenesis.

Paleobotany and Palynology of the Bristol Hill Coal Member (Bond Formation) and Friendsville Coal Member (Mattoon Formation) of the Illinois Basin (Upper Pennsylvanian)

Late Pennsylvanian coal swamps of the Illinois Basin were dominated by Psaronius tree ferns with a spatially heterogeneous distribution of medullosan pteridosperms (subdominant), calamites, sigillarian lycopsids, and cordaites. Miospore and coal-ball plant assemblages from the Missourian-age Bristol Hill Coal Member (Bond Formation) and Friendsville Coal Member (Mattoon Formation) of southeastern Illinois were quantified to analyze vegetational patterns in Late Pennsylvanian peat swamps and to compare vegetational composition of the coals. In the Bristol Hill Coal (95 coal balls, 2613 cm 2 coalball peels), tree ferns are dominant (75.6%), followed by pteridosperms (11.5%), lycopsids (10.6%), sphenopsids (0.6%), small ferns (1.6%), and cordaites (0.1%)

Quantitative Analysis and Paleoecology of the Secor Coal and Roof-Shale Floras (Middle Pennsylvanian, Oklahoma)

The Secor Coal of Oklahoma (Boggy Formation, lower Desmoinesian/Westphalian D equivalent) is one of the few coals discovered, to date, in which Anabathra pulcherrima (=Paralycopodites brevifolius) was a dominant element. Anabathra and Lepidophloios define the major assemblages in the coal, which also contains elements of medullosan pteridosperms and Cardiocarpus spinatus producing cordaites. The Lepidophloios to Medullosa gradient is not obscured by the numerous Anabathra-dominated zones, and a disturbance element is suggested in association with Anabathra abundance. Comparison of the coal-ball flora with a clastic-compression flora from the roof of the coal reveals widely divergent patterns of dominance and diversity. The compression flora is strongly dominated by medullosan pteridosperms with subdominant marattialean tree ferns. As in most instances, the compression flora from the immediate roof of the coal is not an accurate representation of the peat-forming vegetation, at either the level of species composition or the relative abundance of major groups of plants. The swamp and surrounding clastic deltaic environments were edaphically distinct and supported separate floras between which there was limited species exchange.