Jiří Bek

Late Moscovian terrestrial biotas and palaeoenvironments of Variscan Euramerica

A synthesis of the upper Moscovian sedimentological and palaeontological record of terrestrial habitats across the Variscan foreland and adjacent intramontane basins (an area which is referred to here as Variscan Euramerica) suggests a contraction and progressive westward shift of the coal swamps. These changes can be correlated with pulses of tectonic activity (tectonic phases) resulting from the northwards migration of the Variscan Front. This tectonic activity caused disruption to the landscapes and drainage patterns where the coal swamps were growing, which became less suitable to growth of the dominant plants of the swamps, the arborescent lycopsids. They were progressively replaced by vegetation dominated by marattialean ferns, which through a combination of slower growth and larger canopies resulted in less evapo-transpiration. This in turn caused localised reductions in rainfall, which further affected the ability of the lycopsids to dominate the swamp vegetation. These changes were initially localised and where the coal swamps were able to survive the lycopsids and pteridosperms show little change in either species diversity or biogeography, indicating that at this time there was minimal regional-scale climate change taking place. By Asturian times, however, the process had accelerated and the swamps in Variscan Euramerica became progressively replaced by predominantly conifer and cordaite vegetation that favoured much drier substrates. Except in localised pockets in intramontane basins of the Variscan Mountains, the last development of coal swamps in Variscan Euramerica was of early Cantabrian age. Further west, lycopsid-dominated coal swamps persisted for a little longer. The last remnants of the lycopsid-dominated coal swamps in the Illinois Basin disappeared probably by middle-late Cantabrian times, as the cycle of contracting wetlands and regional reductions in rainfall generated its own momentum, and no longer needed the impetus of tectonic instability. This tectonically-driven decline in the Euramerican coal swamps was probably responsible for an annual increase in atmospheric CO 2 of c. 0.37 ppm, and may have been implicated in the marked increase in global temperatures near the Moscovian – Kasimovian boundary, and the onset of the Late Pennsylvanian interglacial.

Two species of Selaginella cones and their spores from the Bohemian Carboniferous continental basins of the Czech Republic.

Two species of Selaginella cones from the Bohemian Upper Carboniferous continental basins of the Bolsovian and Westphalian D age are described, together with their in situ spores. Two specimens of Selaginella gutbierii yielded microspores closely comparable with the dispersed species Cirratriradites saturnii and megaspores closely comparable with the dispersed species Triangulatisporites vermiculatus. Microspores closely comparable with the dispersed species Cirratriradites annulatus and megaspores resemble the dispersed species Triangulatisporites tertius were isolated from cones of Selaginella cf. leptostachys. All the spores isolated from one cone are of the same type and would be referred to one dispersed micro- and megaspore species if found as Sporae dispersae. The paper contains a review of all palynologically studied Carboniferous Selaginella and Selaginella-like cones and reviews of all in situ and dispersed Cirratriradites and Triangulatisporites spores.

Composition and structure of an in situ Middle Pennsylvanian peat-forming plant assemblage buried in volcanic ash, Radnice Basin (Czech Republic)

Abstract 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 m2. 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.

Noeggerathiaceae from the Carboniferous basins of the Bohemian Massif

Abstract Two species of Noeggerathia have been described from the Kladno-Rakovnik, Radnice and Plzeň basins, the Radnice Member (Bolsovian) of the Bohemian Massif. The most complete fossil record is known for Noeggerathia foliosa . The findings of fronds, small trunks and cones of Noeggerathiaestrobus bohemicus enabled a reconstruction of the whole plant to be made. Cuticles, micro- and megaspores have been studied. The genus Noeggerathia is emended. Only small fragments of fronds of Noeggerathia intermedia have been previously found. Five fragments of cones of Noeggerathiaestrobus vicinalis are known. Longitudinally broken strobili and compression/impression specimens confirm the same internal organisation of Noeggerathiaestrobus vicinalis as Noeggerathiaestrobus bohemicus . A new species Archaeonoeggerathia schatzlarensis nov. sp. from the Žacleř Formation (Langsettian) in the Intrasudetic Basin is erected.

Huttonia spicata (Sternberg) emend. and its spores, the Radnice Basin (Bolsovian), Carboniferous continental basins of the Czech Republic

All specimens described as Huttonia spicata by previous authors were re-examined. Eleven specimens of H. spicata from Vranovice, Chomle, Svinna and Břasy localities of the Radnice Basin were studied. Seven specimens are from Sternberg’s original collection stored in the National Museum, Prague, two are from Weiss collection in the Museum fur Naturkunde, Berlin, one specimen comes from the collection of the Czech Geological Survey, Prague and one specimen comes from Naturwissenschaftliches Museum, Vienna. The stratigraphical position of the cones is the Whetstone Horizon, Radnice Group of seams, Radnice Member, Lower Bolsovian. A new family Huttoniaceae is proposed. Huttonia was considered to have more than one sporangium on one sporangiophore. New research confirmed that each sporangiophore bears only one sporangium. In situ micro- and megaspores were isolated from type specimens of the species and are described for the first time from cones undoubtedly assigned to H. spicata. Trilete laevigate microspores are of the Calamospora-type, but most microspores have very thin pseudosaccus-like layer envelopes within the trilete inner bodies. This type of microspore is roughly morphologically similar to that isolated from several cones of Calamostachys and Palaeostachya and may be compared with some dispersed species of the genera Auroraspora, Remysporites, Calliasporites, Perotrilites, Phyllothecotriletes or even Diaphanospora. Laevigate trilete megaspores are of the Calamospora laevigata-type. Palaeoecology of H. spicata is discussed.

Cuticles and spores of Senftenbergia plumosa (Artis) Bek and Pšenička from the Carboniferous of Pilsen Basin, Bohemian Massif

Abstract Senftenbergia plumosa (Artis) Bek and Psenicka is an abundant Carboniferous fern occurring in the Central and Western Bohemian Carboniferous basins of the Czech Republic. Its epidermal structures are described in detail for the first time. The abaxial cuticles are very thin. The cells are isodiametric, random, pentagonal or hexagonal in shape. Stomata occur only on the abaxial side of the pinnules. They are irregularly scattered and more or less oriented in one direction; ca. 200 per mm 2 , of the actinocytic or cyclocytic, flush with the epidermal cells. The abaxial and adaxial surfaces contain small trichome bases. Sporangia are of the Senftenbergia type with Raistrickia type spores. These are different from those of the previously described fertile specimens of S. plumosa from Bohemia, suggesting a large morphological variability of spores in this species. The epidermal structures of S. plumosa are important for understanding the systematic position of this Carboniferous fern. Generally, the cuticle of S. plumosa is more similar (especially its irregularly, polygonal cells with straight anticlinal wall and cyclocytic stomata) to that of living species of Marattiaceae than of Schizaeaceae. The epidermal cells of S. plumosa are very similar to those of the Tedelea glabra . It appears to confirm that S. plumosa is a member of the primitive Carboniferous fern family Tedeleaceae (Jennings and Eggert, 1977; Taylor and Taylor, 1993; Bek and Psenicka, 2001).

Two New Carboniferous Fertile Sphenophylls and their Spores from the Czech Republic

Two new species of sphenophyllalean strobili with in situ spores are proposed from the Radnice Basin of the western and central Bohemian Carboniferous continental basins of the Czech Republic. Bowmanites brasensis sp. nov. from Břasy (Matylda Mine) and B. pseudoaquensis sp. nov. from Ovčín locality are determined mainly on the basis of their spores, which are about 100 µm in diameter. The thick-walled exine of the miospores is laevigate or sometimes very finely scabrate on the proximal contact area. Spores resemble the dispersed species Punctatisporites obesus. Cones of B. brasensis and B. pseudoaquensis are organically connected with stems having prominent blade leaves and represent a new group of sphenophyllalean strobili.

A new morphological type of operculate microspore, Discinispora gen. nov., from the Permian petrified Noeggerathialean strobilus Discinites sinensis Wang

A new morphological type of operculate microspore, Discinispora sinensis gen. et sp. nov., has been isolated from the holotype of Discinites sinensis Wang (Lower Permian, Shitanjing Coalfield, PR China). In these spores a trilete mark with prominent labrum and a circular operculum are located on the same spore wall layer with the operculum occurring on distal surfaces, close to the distal pole. Spherical laevigate inner bodies are trilete. Other Carboniferous operculate microspores isolated from some sphenophyllalean and some Discinites cones have opercula and trilete marks on different spore wall layers. Discinites and some sphenophylls appear to show similar structures in some spore types. These findings also show that at least three different spore types occur in Discinites cones and contribute to the understanding of the complexity of character states in the Noeggerathiales.

Sporophytes of polysporangiate land plants from the early Silurian period may have been photosynthetically autonomous

The colonization of land by vascular plants is an extremely important phase in Earth’s life history. This key evolutionary process is thought to have begun during the Middle Cambrian1 period and culminated in the Silurian/Early Devonian period (interval about 509–393 million years ago (Ma)), and is documented primarily by microfossils (that is, by dispersed spores, phytodebris including fragments of algae, tissues, sporangia and cuticles), tubes and rare megafossils2. A newly recognized fossil cooksonioid plant with in situ spores from the Barrandian area, Czech Republic, is of the highest importance because it represents extremely ancient megafossil evidence of land plant diploid generation: sporophytes (~432 Ma). The robust size of this plant places it among the largest known early polysporangiate land plants and it is probable that it attained adequate size for both aeration and effective photosynthetic competence. This would mean not only that sporophytes were photosynthetically autonomous but also that the they might have been able to sustain a relatively gametophyte-independent existence.Ancient fossil Cooksonia plants from the Czech Republic are among the largest known early polysporangiate plants from when vascular plants were colonizing the land. They were of sufficient size to support effective photosynthesis.

Revision of Pennsylvanian genus Sturia Němejc and its spores (Duckmantian, Czech Republic)

Abstract Sturia amoena (Stur) Němejc is a Pennsylvanian adpression true fern known from the Charbonnière de Belle et Bonne (Belgium) and from the Radnice and Kladno-Rakovník basins (Czech Republic). This revision includes a detailed study of pinna and pinnule morphology, aphlebiae and reproductive organs. Interesting details of sporangia and in situ spores are described for the first time. The sporangia of Sturia amoena have an equatorial bi-triseriate annulus and yielded in situ spores of the Punctatisporites and Apiculatisporites types.