Systematics of the Late Carboniferous Medullosalean Pteridosperm Laveineopteris and Its Associated Cyclopteris Leaves

Laveineopteris is emended to become a morphogenus for the vegetative parts of certain medullosalean pteridosperms that grew in the Westphalian (Late Carboniferous) tropical rainforests. The plant bore pinnate foliage as sun leaves and entire orbicular leaves (cyclopterids) as shade leaves. The cyclopterids were attached to the axis of the saplings and epiphyllously to the lower parts of the pinnate fronds. Species recognition is mainly by the macro–morphology of the pinnate fronds. However, species can also be distinguished based on the epidermal anatomy of both pinnate fronds and cyclopterids, in particular the distribution and detailed structure of the stomata and hydathodes. Laveineopteris first appeared in the lowland swamp forests of Europe during the early Langsettian (Westphalian A), and there were two principal species: L. loshii and L. tenuifolia . During the early Bolsovian (early Westphalian C), a variety of L. tenuifolia appeared that was adapted to both the lowland swamps, and the upland swamps of the intramontane basins (central Bohemia and Saar–Lorraine). The smaller–pinnuled L. rarinervis also first appeared in the Bolsovian and seems to have been restricted to the lowland swamps. The morphogenus Cyclopteris should be used only for cyclopterid fossils, where they cannot be related to the species of Laveineopteris , Callipteridium or Margaritopteris that originally bore them.     

Reconstitution d'un « paysage de l'époque houillère » revue à la lumière des découvertes récentes sur les cuticules végétales fossiles

To date, plants with a climbing or scrambling growth habit are widely represented in equatorial forest ecosystems, with a warm and humid climate, with a variety of different species. Although it has been speculated repeatedly that several Late Carboniferous seed ferns applied the same growth strategies as modern vines and /or lianas, only few examples have been substantiated in sufficient details. Most Paleozoic seed ferns are reconstructed as free-growing erect trees. However, these last years, new discoveries about the growth habits of fossil plants have been highlighted on the basis of cuticular material. In this way, different types of climbing organs of seed ferns, reported on pteridosperm cuticles collected from the Stephanian basin of the Blanzy-Montceau (central France), have revolutionized the stereotype of “free-growing erect trees” that we had about these plants. These discoveries demonstrate the potential of cuticular analysis for the reconstruction of growth habits of fossil plants. Moreover they exemplify that climbing and scrambling became common life strategies among Late Carboniferous seed ferns. The increasing proportion of climbing seed ferns in the Stephanian, interpreted as an expression of changing structures of Late Paleozoic coal swamp forests, lead to modify the “classical” reconstructions of the Late Carboniferous landscapes.     

STEM AND LEAF CUTICLE OF KARINOPTERIS: SOURCE OF CUTICLES FROM THE INDIANA “PAPER” COAL

Cuticular or “paper” coal-shale is a local deposit of an organic-rich, highly clastic rock, with abundant leaf and stem cuticles, associated with the Upper Block Coal Member in Parke County, Indiana. Fresh blocks of cuticular coal can be split along bedding surfaces to reveal a fossil flora of low diversity, dominated by pteridosperms and lycopods, with minor amounts of ferns and sphenopsids. Karinopteris is a subdominant component of this flora and the great abundance of well-preserved cuticles of this plant allows for a reconstruction of its frond and growth habit. Karinopteris appears to have been a vine, indicative of structural diversity in the plant assemblage. The plant assemblage of the cuticular coal is dissimilar to most midwestern coal-ball floras of slightly younger age. This is probably a result of the depositional setting in an upper deltaic-fluvial dominated environment.     

Palaeogeography of the late palaeozoic in the bohemian massif

The palaeogeographic and palaeoclimatic setting of the Bohemian Massif is documented with maps for the following seven stages: Westphalian A, Westphalian B to Westphalian D, Stephanian A, Stephanian B, Stephanian C to Autunian, Saxonian and Thuringian. The evaluation of present occurrences and of the presumed area of sedimentation makes the palaeogeographic picture more comprehensive. Because of the relatively long time intervals represented on the maps, the palaeogeography is expressed in terms of the ratio of different environments in the total sedimentary fill. For the units deposited under a predominantly humid climate, we distinguish between sediments of foothills, alluvial fans, flood plains, lacustrine deltas, perennial lakes, peats and swamps. For the units deposited under semi-arid to arid climatic conditions, sediments of pediplains, alluvial fans or of the alluvial apron were suggested for the margins, and sediments of flood plains, ephemeral and perenial lakes, peats and swamps for the central part of the sedimentary basins. The development of the sedimentary area and of its fill was influenced by diastrophism and particularly by the climate. The rate of sedimentation was controlled by the contemporaneous subsidence. Changing climatic conditions exerted a strong influence on the regionally important fluctuations in the size and shape of the area of sedimentation and on the character of the material deposited. From Westphalian to Austinian times the area of sedimentation was generally expanding. During the Saxonian and Thuringian, the area of sedimentation was reduced. This reduction was caused by the tectonic stabilization and peneplanation of the central part of the Bohemian Massif and the appearance of typical desert climatic conditions.     

The Westphalian fossil floras from the Cattybrook Claypit,avon (Great Britain)

Cattybrook Claypit, on the northwest margin ofthe Bristol-Somerset Coalfield, yields an upper Westphalian A (Middle Carboniferous) fossil flora. Most of the fossils are of small plant fragments, transported mainly by winds into floodbasin muds. They represent a variety of plant-types, including pteridosperms, ferns, cordaites, sphenophytes and lycophytes. Of particular interest are finely preserved examples of Lonchopteris, and Corynepteris, which are generally scarce in British floras of this age. Also found at Cattybrook are plant fragments in a crevasse-channel sandstone. These are preserved nearer their original position of growth, and are thus more complete than those found in the floodbasin deposits. They include almost complete fronds of Karinopteris attached to a thick lianatype stem, and large pieces of a Sphenophyllum plant. This is now the best documented late Westphalian A flora in Britain.     

Pennsylvanian miospore assemblages from the Bèdero Section,Varese, Italian Southern Alps

Thin continental Carboniferous sequences crop out sparsely in the western Southern Alps (Alpe Logone, Mesenzana, Grantola, Bosco Valtravaglia-Fabiasco, Val Tresa, etc.) and are currently the subject of a detailed litho- and biostratigraphic revision, to reconsider their chronological position with respect to previously published age constraints. The age of these Upper Palaeozoic sedimentary successions, scattered over a wide area and strongly tectonized along major structural lineaments, has long been debated between Westphalian and Stephanian. The present work focuses mainly on the palynology of the Brezzo di Bèdero section (Luino, Lake Maggiore). The recovered palynoflora is assigned to 42 spore genera and 76 species of which one genus and 10 species are newly proposed. Fifty-seven spore species and 19 pollen species are described and illustrated. Qualitatively, the Bèdero palynoflora shows strong affinities to those of Western Europe. The most abundant palynomorphs are trilete spores known to be characteristics of the late Westphalian and early Stephanian assemblages. These are characterized by the remarkable presence of Florinites and subordinately Wilsonites species, low numbers of Potonieisporites, rare Limitisporites and Vesicaspora, and very rare Latensina-Cordaitina pollen. The occurrence of diverse monolete spores Laevigatosporites, Punctatosporites, Spinosporites, Thymospora and Torispora, with common Lundbladispora gigantea, L. simonii, Stenozonotriletes rubius n. sp. together with the absence of plicate and taeniate pollen grains suggests a strong resemblance to the late Westphalian–early Stephanian interval assigned to the OT Zone of Western Europe. Variations in the quantitative composition can be likely attributed to variations in the environmental setting with regards to non-forming peat deposits. The palynological suite is indicative of the existence of a well-established lowland Cordaiteans vegetation and well settled pterophytic, pteridosperm and subordinately sphenophytic and lycophytic, hygrophytic plant communities.     

New Observations on the Branching of Carboniferous Ferns and Pteridosperms

Additional information is presented on the oldest known exampleof axillary branching seen in some Calamopitys from the lowermostCarboniferous of France; these putative pteridosperms are amongstthe earliest plants to be attributed to the spermatophytes.Comparative anatomical studies of coenopterid ferns from theLower and Upper Carboniferous show four categories of caulinebranching morphology: unbranched, dichotomous, lateral-monopodialand branches borne on leaves. It is suggested that leaf evolutionand thus, the axillary type of branching, was achieved earlierin the pteridosperms than in the ferns. Calamopitys, pteridosperms, coenopterid ferns, axillary branching, stem dichotomy, evolution, Carboniferous, fossil anatomy     

Réflexion sur la coexistence de flores hygrophile,mésophile et mésoxérophile durant le Paléozoïque Supérieur en Euramérie

At the end of Namurian A, in Eurameria, we see agreat change in the composition of the flora, probably instigated by a great modification in the climatic conditions. This flora adapted to very humid places persist during whole the Westphalian and up to the end of Stephanian where it is relayed by a mesoxerophytic flora of which the most typical elements are the Coniferales of the family Lebachiaceae. This «autunian flora is usualy considered as subsequent to the stephanian hygrophytic flora and as the transition to the permian flora which is determined by a new modification of the general climatic conditions.Some observations about the macroflora and about the microflora lead to prove the coexistence of hygrophytic, mesophytic and mesoxerophytic floras, not only during the upper Stephanian but also during Westphalian and Namurian B and C. So, from Devonian to Permian, in Eurameria, there was probably continuity of a mesoxerophytic and mesophytic type floras on which was superimposed during the upper Carboniferous an hygrophytic flora adapted to the swamps surrounding the coal-lakes and coal-lagoon. The time of the appearance of Coniferales is older as we think usually.     

THE VEGETATIVE ANATOMY OF SCHOPFIASTRUM DECUSSATUM FROM THE MIDDLE PENNSYLVANIAN OF THE ILLINOIS BASIN

Schopfiastrum decussatum, a monostelic pteridosperm, has been recovered from Middle Pennsylvanian age coal balls from six localities within the Illinois Basin. Additional features of stem anatomy include the presence of horizontal sclerotic plates in the inner cortex, secretory ducts in the inner and outer cortex, and adventitious roots. The primary xylem is interpreted as bilobed, emitting massive leaf traces in a distichous manner. Five orders of frond members are described, including pinnules. All orders of the frond contain secretory ducts and tissues characteristic of Schopfiastrum stems. The rectangular, bilobed protostele, and method of leaf trace origin indicate that Schopfiastrum is more closely related to certain lower Carboniferous seed ferns than to contemporary Pennsylvanian pteridosperms.     

LYCOSPORA FROM CARBONIFEROUS LEPIDOSTROBUS COMPRESSIONS

Spores were extracted from Carboniferous Lepidostrobus compressions in order to associate in situ microspores with dispersed species of Lycospora. Two hundred twenty-six cones were examined, of which 61 contained spores. Fertile cones came from the Westphalian D of England, Namurian B through Westphalian D of the Appalachian and Illinois basins, and the Westphalian D of the Western Interior. Cones were separated into species based on microspore and cone morphology. Lycospora trigonoreticulata was produced by Lepidostrobus princeps from Westphalian C-D rocks from Missouri, the Illinois Basin, and the Appalachian Basin. Lycospora rotunda was produced by Lepidostrobus sp. A from Westphalian A rocks of Alabama. Two cone species produced Lycospora torquifer: Lepidostrobus praelongus from the Westphalian D of Pennsylvania and Lepidostrobus variabilis from the Westphalian A and C of the Illinois and Appalachian basins. Lycospora punctata was produced by Lepidostrobus cf. squarrosus from the Westphalian D of England, the Appalachian Basin, and Illinois Basin. Lycospora noctuina was produced by Lepidostrobus haslingdenensis from the Namurian B/C of Illinois. Microspore species are differentiated primarily on the basis of size, cingulum structure and width, and ornamentation. Cone species differ in width and distal lamina size, shape, and attitude. Lycospora species isolated from clastic species of Lepidostrobus differ completely from those of coal-swamp species, confirming that lycopod trees from clastic environments represent biologically different species from those centered in coal swamps.     

Synthèse sur la flore des nodules du Lagerstätte de Montceau-les-Mines (Carbonifère supérieur,France)

The flora from the Montceau-les-Mines Lagerstätte (Late Pennsylvanian, Stephanian, France) is preserved in small sideritic nodules and was studied in three locations in the (1) Saint-Louis, (2) Saint-François, and (3) Sainte-Hélène opencast mines. Qualitative and quantitative analyses of plant diversity and floristic composition in about 7000 nodules indicate substantial variations in the floral composition of these opencast mines. More than 50 taxa are recognized and belong to groups typical of the Late Carboniferous flora (lycopsids, sphenopsids, tree ferns, and pteridosperms). Arborescent sphenopsids and tree ferns were the major components at Saint-Louis, whereas the flora from Saint-François consisted mainly of pteridosperms; the one from Sainte-Hélène has a more balanced composition. Taphonomic and sedimentological data show that the flora contained in the nodules was hypoautochthonous to parautochthonous. The Montceau Basin displayed a mosaic of paleoenvironments (e.g., deltaic lacustrine, paludal to fluvial) which favored colonization by plants and animals.     

The Montceau-les-Mines Lagerstätte (Late Carboniferous,France)

The Montceau-les-Mines Lagerstätte (Late Stephanian, Late Carboniferous) is located northeast of the French Massif Central. Situated at equatorial latitudes during the Pennsylvanian, this Lagerstätte, probably a freshwater environment, preserves a rich and diverse flora (lycopsids, sphenopsids, ferns, pteridosperms, and cordaites) and fauna (bivalves, annelids, crustaceans, myriapods, insects, chelicerates, myxinoids, actinopterygians, sarcopterygians and tetrapods). These exceptionally preserved fossils can be found either flattened in shales or three-dimensionally preserved in sideritic nodules. The fossils from the nodules are exceptional for at least two reasons: the absence of major disarticulation of their body structure and the preservation of soft parts and extremely fragile cuticular structures. Such preservation was made possible by the combination of several factors: rapid burial in fine anoxic mud, early siderite precipitation (inducing the nodule formation) and phosphatization of cuticles and soft-bodied features.     

Plant/animal interactions during the upper carboniferous

This paper discusses evidence for plant/animal relationships in the Upper Carboniferous. Close interactions are examined from the study of fossil plants and animals preserved in coal swamp and coastal plain environments. Evidence for plant/animal interactions is in the form of: (1) animal morphology, including both vertebrates and invertebrates. The vertebrates are dominated by amphibians; however, a few reptiles are known and are mostly carnivores or insectivores. The invertebrate communities are dominated by arthropods, many of which are herbivores. Millipedes, springtails and mites are present on the forest floor and in peats, with insects dominating above ground environments. The diets of the animals have been studied using evidence from gut contents, coprolites, anatomy and comparisons to modern representatives. (2) Plant morphology, including positive stimulation (i.e., dispersal vectors) or in terms of negative stimulation such as protection against herbivory. These data include plant anatomy and morphology, evidence of herbivory in the form of chewed leaves, bored seeds and megaspores, etc. Evidence is provided that suggests that the medullosan seed fern pollen typeMonoletes may have been dispersed by animal vectors. Information on plant/animal relationships in a single environment is based on a study of coprolites extracted from permineralizations (coal balls). Assemblages of coprolites found in these coal balls suggest that they were formed principally from mites, Collembola and millipedes, and demonstrates that the association of soil arthropods, which is important in modern soil ecosystems, was already dominating similar environments in the late Carboniferous. The abundant fossil evidence for plant/animal interrelationships during the Upper Carboniferous should be evaluated when considering co-evolution.     

Palaeoecological evolution of Duckmantian wetlands in the Ruhr Basin (western Germany): A palynological and coal petrographical analysis

For this study, six seam sequences of Duckmantian age from the Ruhr Basin, western Germany, were analysed. 155 samples from drill cores were examined, including coal samples, as well as organic-rich and clastic sedimentary rocks. All samples were analysed using palynological and coal petrographical techniques. Based on published information of in situ miospores the encountered dispersed miospores were assigned to their parent plants in order to reconstruct the vegetation history. Six vegetational associations were identified using Detrended Correspondence Analyses (DCA): lepidocarpacean association I, lepidocarpacean association II, lepidocarpacean-sigillarian association, lepidocarpacean-sphenophyll association, lepidocarpacean-fern association, and the subarborescent lycopsid association.Lycospora is the most important constituent in the miospore association as in 75% of all samples the genus is represented with more than 50% relative abundance. Lepidocarpaceans such as Lepidophloios and Lepidodendron are very common among the plant fossils. Hence, arborescent lycopsids dominated the vegetation of the Ruhr Basin during the mid and late Duckmantian, forming flood plains and planar forest mires. Variations in the plant environment are reflected by greater influence of sigillarians, which were typical for swamp margins or for domed swamps, characterized by stunted vegetation. Fern-dominated environments were rare during the Duckmantian.A typical rhythmic succession shows an evolution from clastic flood plains through peat substrate planar mires, followed by a doming of the swamps and formation of ombrogenous mires. Floodplains reappeared during periods of subsidence, accompanied by a rise in water level.     

CAULINE VASCULATURE AND LEAF TRACE PRODUCTION IN MEDULLOSAN PTERIDOSPERMS

Medullosa and Sutcliffia specimens from the Paleozoic of North America and Europe are examined to determine the architecture of the cauline vasculature and mode of leaf trace production. Emphasis is placed on the identification and characterization of protoxylem strands and their relationship to leaf trace production. Organization of the primary xylem varies from a single protostele to a dissected stele composed of two to many more or less independent bundles. In Medullosa the bundles of primary xylem are each surrounded by secondary xylem, forming separate segments of vascular tissue (‘steles’ of previous workers). These vascular segments may divide and fuse at different levels in the stem. A definite number of protoxylem strands occur near the periphery of the primary xylem. The protoxylem strands divide at intervals producing protoxylem to the departing leaf traces. Leaf traces thus formed arise from all the vascular segments in a coordinated and predictable way and pass outward through emission areas in the secondary xylem. This type of cauline vascular architecture is compared to that of other seed plants. The vascular system of Medullosa stems is interpreted as a dissected monostele. Sympodial vascular architecture has apparently evolved from a protostele separately within the medullosan pteridosperms.     

Phylogénie générale des Calliptéridiacées (Pteridospermopsida)

The study of the evolutionnary trend of the leaf architecture in the genus CallipteridiumWeiss, from the upper Westphalian and Stephanian, has allowed to determine, by extrapolation, the characters that had to show the frond of the direct ascendants which belong to the genus MargaritopterisGothan, from the Westphalian. This clue has led the quest on the field and has enabled the discovery of data which verify the correctness of the formulated hypothesis. This positive result and the evolutionnary trend ascertained by this new portion of the phylum led us to propose a new hypothesis about the characters of the fronds of the more ancient representatives of the phylum, that one can trace with great probability up to the lower Namurian and more hypothetically up to the Dinantian.This work has carried otherwise a revision of the corresponding species from the North of France and Sarre-Lorraine coal basins with a certain number of consequences about stratigraphical correlations.     

Morphologic variability of Pennsylvanian lyginopterid seed ferns

The current level of understanding of the morphological variability of Pennsylvanian lyginopterid seed ferns is reviewed. This group of pteridosperms that ranges throughout the Carboniferous is represented by a heterogeneous assemblage of stems, leaves, ovules and pollen organs. Vegetative organs have been useful in tracing the origin of the eustele from a protostele, while the fern-like fronds appear to have had their origin from a non-planated branching system. The small radially symmetrical ovules, while exhibiting some diversity in the organization of integument, demonstrate little apparent alteration in pollen-receiving mechanisms and reproductive versatility. Lyginopterid pollen organs are synangiate and include both radial and bilateral forms. The stratigraphically earliest types are radial and borne upright on naked branches, while later forms are usually bilateral and typically associated with laminar foliage. Pollen is morphologically and structurally similar to the spores of many ferns, and probably germinated through the proximal suture. The apparent homogenous nature of lyginopterid seed ferns may indicate that relatively little evolution had taken place over a long geological time span. However, evidence from some compression floras suggests that far more diversity exists within the order in a non-swamp environment than had previously been thought. Current concepts about lyginopterid pteridosperms that have been developed from a small group of plants in a relatively homogeneous environment may need considerable revision as we learn more about the non-swamp inhabiting forms.     

The effect of heat and smoke on the soil seed banks of heathlands on permanent freshwater swamps

In South Australia, Swamps of the Fleurieu Peninsula are critically endangered due to past vegetation clearance and changes in hydrology, but still contain a high diversity of threatened plant species. This vegetation community provides habitat for 82 threatened ground-stratum plant species, including the nationally critically endangered subshrub Hibbertia tenuis which is endemic to these swamps. With infrequent burning, native ferns and taller shrubs outcompete these species. We conducted glasshouse trials to determine the potential of fire to regenerate threatened and other swamp plant species. Soil samples from eight swamps were used in germination trials with half of each sample treated with heat plus smoke, and half left untreated. Samples were spread onto trays (n = 188), and seedling emergence was recorded for twelve months. Emergence was dominated by native species (2649 seedlings m⁻²) compared to exotics (675 seedlings m⁻²). In total, 48 native and 25 introduced species germinated, with 21% of germinated native species absent from the above-ground vegetation. The dominant native fern Gleichenia microphylla did not emerge from any soil samples, indicating that recovery likely lags behind that of ground-strata species, giving them time to establish and set seed before being outcompeted. Thirty-four rare or threatened species germinated, including five species absent from above-ground vegetation. Of all native species that emerged, only five were confined to heat plus smoke treatments, suggesting most species will regenerate without fire if overstorey competition is reduced. However, seedling emergence of native shrubs/subshrubs more than doubled with the fire treatment. Of particular importance, H. tenuis showed an 18-fold increase in germination when treated with heat plus smoke. This study supports the utility of ecological burns as a management tool to regenerate threatened plant species in long-undisturbed peaty heathlands on permanent swamps.     

SEED BANK DYNAMICS IN A SOUTHEASTERN RIVERINE SWAMP

Seed banks were examined in a Taxodium distichum L.-Nyssa aquatica L. (cypress-tupelo) swamp forest and an adjacent bottomland hardwood forest on the floodplain of the Savannah River in South Carolina. Thirty 0.01 m² soil cores were collected in each community at each of three sampling times: before seed fall, after seed fall, and after an early spring river level rise had inundated both communities. Germination and sieving techniques were used to enumerate seeds in each sample. Woody seed banks of the two communities were dissimilar in species composition with both underrepresenting the species composition of the standing vegetation. In contrast, herbaceous seed banks of both communities were similar in species composition with greater species diversity in the seed banks than in the standing vegetation. Both the herbaceous and woody seed banks of the hardwood community changed significantly in seed densities across the three collection dates. Densities increased from September to December, after seed fall for many species, but decreased in April after the early spring water level rise. Seed densities did not change significantly in the cypress-tupelo community across the three collections. Hydrologic regime appears to have a major influence on seed bank composition and dynamics in southeastern riverine swamps.