Late Ludlovian Chitinozoa from the locality “Na Požárech” (Silurian, Prague Basin, Barrandian area, Czech Republic)

Laboratory-scale experimental burning of three facial types of Devonian limestones from the Barrandian area (Czech Republic) revealed their suitability for production of natural hydraulic lime and/or natural cement of variable degrees of hydraulicity. Although employed as a raw material for ordinary Portland cement at present, all these limestones must be blended to achieve the optimum composition required for ordinary Portland cement clinker. However, if burnt in their natural state (i.e. without any further addition of SiO2, Al2O3 and/or Fe2O3), and by using a sufficiently coarse grained batch, they exhibit favourable content of newly formed hydraulic phases. These are controlled not only by overall mineralogical/chemical composition of a raw material, but also by burning conditions, specifically by peak temperature and its duration. Prevalent dicalcium silicate (larnite) plus some minor calcium aluminosilicates (gehlenite) or aluminoferrites (brownmillerite) form due to solid state reactions between homogeneously distributed non-carbonate fraction (silica minerals, clay minerals, feldspars) in micritic carbonate groundmass.

Microboring organisms — an overlooked Early-Mid Palaeozoic marine ecosystem: Case study from the Prague Basin (Czech Republic)

The most ancient macroscopic plants fossils are Early Silurian cooksonioid sporophytes from the volcanic islands of the peri-Gondwanan palaeoregion (the Barrandian area, Prague Basin, Czech Republic). However, available palynological, phylogenetic and geological evidence indicates that the history of plant terrestrialization is much longer and it is recently accepted that land floras, producing different types of spores, already were established in the Ordovician Period. Here we attempt to correlate Silurian floral development with environmental dynamics based on our data from the Prague Basin, but also to compile known data on a global scale. Spore-assemblage analysis clearly indicates a significant and almost exponential expansion of trilete-spore producing plants starting during the Wenlock Epoch, while cryptospore-producers, which dominated until the Telychian Age, were evolutionarily stagnate. Interestingly cryptospore vs. trilete-spore producers seem to react differentially to Silurian glaciations—trilete-spore producing plants react more sensitively to glacial cooling, showing a reduction in species numbers. Both our own and compiled data indicate highly terrestrialized, advanced Silurian land-plant assemblage/flora types with obviously great ability to resist different dry-land stress conditions. As previously suggested some authors, they seem to evolve on different palaeo continents into quite disjunct specific plant assemblages, certainly reflecting the different geological, geographical and climatic conditions to which they were subject.

Magnetostratigraphy susceptibility of the Přı́dolian–Lochkovian (Silurian–Devonian) GSSP (Klonk, Czech Republic) and a coeval sequence in Anti-Atlas Morocco

Feeding traces related to shells from the Prague Basin, Czech Republic (Tremadocian to early Darriwilian, Ordovician)

Epibionts on shells in the Šárka Formation: a sparsely occupied niche in the lower to middle Darriwilian (Oretanian, Ordovician) in the Prague Basin (Czech Republic)

Arthrorhachis Hawle and Corda, 1984 (Agnostida) in the Prague Basin (Barrandian area, Czech Republic) revisited

A new Late Ordovician echinoderm Lagerstätte in the Prague Basin (Barrandian area, Czech Republic)

The Devonian micritic limestones from the Prague Basin (Barrandian area, Bohemian Massif, Czech Republic), which were the primary raw material used for natural hydraulic lime burned in Prague, exhibit a feebly to eminently hydraulic character. Based on a laboratory experimental study, the burned product is composed of dominant free-lime (CaO) and/or portlandite (Ca(OH)2), larnite-belite (bicalcium silicate 2CaO.SiO2), and quartz (SiO2) - i.e. phases formed due to the decomposition of carbonate and quartz, present in the original limestones. Proportions of the newly formed phases depend on: the composition of the raw material, maximum burning temperature (the highest amount of larnite-belite appearing at a burning temperature of 1200 °C), and the granulometry of the experimental batches (a coarsely-ground batch exhibited a higher amount of larnite-belite compared to the finely-ground one). The presence of minor phyllosilicates in the raw material contributed to the formation of gehlenite, brownmillerite, wollastonite, calcium aluminate, and/or spurrite.

Cuticular remains of the phyllocarid crustaceans Caryocaris? and Ceratiocaris? obtained via maceration of macrofossil remains in hydrofluoric acid are compared with dispersed fragments isolated using both the low-manipulation HF extraction and the standard HCl–HF–HCl method. The studied specimens were obtained from Ordovician and Silurian shales of the Šárka and Požáry formations (Prague Basin, Barrandian area, Czech Republic). This methodological approach allows a direct comparison of macrofossil remains with microfossils in residue. The differences in residues obtained through the two bulk-rock extraction methods are also discussed.

Brachiopod etching trace Podichnus, typically with centrifugally arranged clusters of holes or slits, has hitherto been known only in calcium carbonate substrates. The similar etching trace is newly described on calcium phosphate substrate. The trace Podichnus isp. in a wall of a phosphatic byronid test was observed in the lower Devonian Vinařice Limestone (Pragian) in the Koněprusy area of the Prague Basin in the Barrandian area, the Czech Republic. The trace is smaller that majority of described species of this fixichnia, and displays a smooth central disc surrounded by two circlets of holes or pits. Some holes penetrate through wall of byronid test without any biotic response of a byronid. The maker of Podichnus isp. is uknown but among the associated fossils are eligible candidates including rhynchonellids, orthids and terebratulids. It is rare direct evidence of etching activity of the pedicle in the Lower Palaeozoic and the first finding of Podichnus in the Devonian in the Prague Basin. The emended diagnosis of the ichnogenus is presented herein.

The succession of 38 upper Llandovery–lower Wenlock chitinozoan taxa from graptolitic horizons in the Banwy River section (Powys, Wales) is described. Five new species are named: Bursachitina nestoraeConochitina leviscapulaeConochitina mathrafalensisBelonechitina caveiBelonechitina meifodensis. A further ten taxa are described under open nomenclature. Seven chitinozoan biozones are recognized in the Banwy River section, three of which (Cingulochitina bouniensisConochitina acuminataSalopochitina bella) are new. The base of each biozone is correlated with the graptolite biostratigraphical scheme as follows: Angochitina longicollis Biozone — upper spiralis Biozone; Conochitina acuminata Biozone — lowermost lapworthi Biozone; Margachitina banwyensis Biozone — upper lapworthi Biozone; Margachitina margaritana Biozone — lowermost insectus Biozone; Cingulochitina bouniensis Biozone — upper murchisoni Biozone; Salopochitina bella Biozone — upper firmus Biozone. The succession of chitinozoan biozones in the Banwy River section is compared with that in other sections which have graptolite biostratigraphical control. This has highlighted the following: (1) the correlation of the base of the dolioliformis Biozone with the graptolite biozonation is imprecise; (2) E. dolioliformis is recorded only from levels after the first A. longicollis in Sweden (although this may reflect previously unrecognized synonymies); (3) the longicollis Biozone may be diachronous, its base correlating with levels low in the Telychian in Sweden, Norway and Estonia and with the upper Telychian spiralis Biozone in Wales and the Prague Basin; (4) data herein and from the Prague Basin indicate that the base of the margaritana Biozone correlates with a level low in the insectus Biozone.

This study adds new data to complete the taxonomic revision of arthrodire placoderms from the Early Devonian of the Prague Basin (Czech Republic). It focuses on re-describing arthrodire specimens from the Emsian strata published more than a hundred years ago and associating them with unpublished material. The observations contradict previous taxonomic determinations of the Emsian arthrodires, which distinguished four species of three genera. Only one new genus and species is recovered—Johannaspis bohemicus (Barrande, 1872). The previous taxonomic splitting of the material into various genera is explained as a factor of specific taphonomical preservation in different localities of the Prague Basin. Another factor enabling the artificial splitting was the present location of the material in different institutions around the world. Together with Antineosteus rufus Vaškaninová & Kraft, 2014 based on previously unpublished specimens, they are the only two placoderm species known from the Emsian of the Prague Basin. Both are assigned to the homostiid arthrodires—large suspension feeders. The abundance of the Emsian placoderm fauna is very low in the Prague Basin; only a few specimens are known from each locality. However, they occur in a number of localities of Emsian age in the Prague Basin and in different environments, from very shallow (A. rufus) to relatively deeper marine environments, with all the occurrences being in limestones. The palaeogeographical distribution of homostiid arthrodires in the late Early Devonian was limited to tropical and subtropical shallow marine environments mainly in the southern hemisphere. In the Middle Devonian, the homostiids are no longer recorded from the northern continental margin of Gondwana including the Prague Basin area. However, they appear in Laurussia, Siberia and eastern Gondwana. The disappearance of environments with abundant food resources favourable for these large suspension feeders in the Prague Basin area could be related to the narrowing of the Rheic Ocean and gradual emerging of dry land as an early manifestation of the proceeding Variscan orogeny. This specific local palaeogeographical development of the Prague Basin area is considered the main reason for the significant decrease in diversity and abundance of placoderm fauna, which is in contradiction to the general trend.Valéria Vaškaninová [va.vaska@gmail.com], Institute of Geology and Palaeontology, Faculty of Science, Charles University, Albertov 6, Prague, 128 43, Czech Republic.

Klapper, G. and Vodražkova, S. 2013. Ontogenetic and intraspecific variation in the late Emsian - Eifelian (Devonian) conodonts Polygnathus serotinus and P. bultyncki in the Prague Basin (Czech Republic) and Nevada (western U.S.). Acta Geologica Polonica, 63 (2), 153-174, Warszawa. Samples from populations of Polygnathus serotinus Telford 1975 and P. bultyncki Weddige 1977 from the Prague Basin and Nevada display normal variation for Devonian conodont species. A considerable number of previous authors, however, have proposed unnecessary synonyms of these two species, primarily because they have not recognized ontogenetic variation. In contrast, we interpret the variation as ontogenetic as well as intraspecific and present detailed synonymies as a result. A third species, P. praetrigonicus Bardashev 1992, which has been carried in open nomenclature for many years, is an important indicator of the basal costatus Zone in the Prague Basin, New York, and Nevada. We review the stratigraphic distribution of these three species and the conodont zonation across the Emsian-Eifelian (Lower-Middle Devonian) boundary. Polygnathus pseudocostatus sp. nov. (partitus-costatus zones, central Nevada) is described herein. We have observed a decrease in the pit size during ontogeny in P. bultyncki although we have not measured enough specimens to rule out intraspecific versus ontogenetic variation.

Abstract. Highly-diversified assemblages of dispersed trilete miospores and cryptospores belonging to the Artemopyra brevicosla-Hispanaediscus verrucous Assemblage Zone were recovered from upper Wenlock (Silurian) tuffitic shales and limestones in the Prague Basin (Bohemia). The fact that the numerous sporomorphs have only been found in the region of the Svatý Jan Volcanic Centre supports previous sedimentological evidence that this volcanic elevation was emerged during the uppermost Wenlock. Twenty-nine sporomorph forms were determined. One new genus, Rugosisporites gen. nov., and three new species, Rugosisporiies kozlicus sp. nov., Synorisporites maculosus sp. nov. and Artemopyra rugaticosta sp. nov. are described. The comparison with other coeval assemblages is discussed.