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The shale-dominated hemipelagic succession exposed in the southwestern part of the Prague Synform preserves the most complete Ludfordian graptolite record so far encountered from peri-Gondwanan Europe. Four graptolite biozones -the Neocucullograptus inexpectatus, Nc. kozlowskii, Pseudomonoclimacis latilobus-Slovinograptus balticus and Pristiograptus fragmentalis biozones -are recognized in the middle and late Ludfordian, between the Bohemograptus tenuis Biozone and the base of the Pridoli Series. Conodont occurrences are restricted to scattered limestone beds, but enable tentative integration of the graptolite and conodont biozonal schemes. Particular attention was paid to faunal and sedimentary changes and the carbon isotope record across the middle Ludfordian Kozlowskii extinction Event. The Kozlowskii Event caused the almost simultaneous extinction of graptolites with ventrally curved rhabdosomes. The genera Bohemograptus, Polonograptus and Neocucullograptus, along with Pseudomonoclimacis dalejensis, disappeared from the fossil record. The offshore conodont fauna recorded in the section was not strongly affected and similarly the pelagic orthocerids and nektonic Ceratiocaris passed unaffected through the extinction interval. The abundant and widespread pelagic myodocopid ostracod Entomis, however, became extinct. The late Ludfordian graptolite recovery gave origin to a novel fauna of Pridoli type from taxa that emerged or just reappeared above the Kozlowskii crisis. In Všeradice and elsewhere in the Prague Synform, the recovery, manifested by the appearance of Pseudomonoclimacis latilobus and Slovinograptus balticus, closely postdates the end of the isotope excursion but pre-dates the first appearance of the conodont index 'Ozarkodina' snajdri. Here the graptolite recovery was delayed relative to the recovery of the benthic fauna. A canalized intraformational limestone conglomerate corresponds with a gap in the sedimentary record above the Kozlowskii extinction and just below the graptolite recovery. The benthic faunas from the conglomerate matrix and pebbles permit correlation with the shallower part of the basin indicating a distinct fall in sea-level. The present data demonstrate the coincidence of the graptolite crisis with benthic faunal change and eustatic fall in sea-level manifested by facies change and the carbon isotope excursion. Polonograptus chlupaci sp. nov., from the Nc. kozlowskii Biozone, is described and several other graptolite taxa are redescribed.

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Conodont faunas of the Polygnathoides siluricus Zone (Ludfordian, Ludlow) from shallow-water environments of Bohemia are characterized by relatively high taxonomic diversity that reflects an interval with taxa thriving due to increased nutrient supply in rather stable environments during the pre-Lau Event time, as has been documented globally. Although the conodont faunas in strata with P. siluricus are more diversified and variable than those in the interval instantly following, the uninterrupted ranges of several taxa (of genera Wurmiella, Ozarkodina and Delotaxis) show that the change in conodont faunas in the sections is not as drastic in Bohemia as described on Gotland and that the extinction rate was rather moderate. A detailed correlation of conodont distribution in the sections indicates, however, that a large part of the Lau Event is not preserved in the shallow water environment of the former Řeporyje Volcanic Elevation. Accordingly, timing and spatial image of the conodont extinction are thus partly obscured. Only a short interval with considerably diminished conodont elements during the lower range of Ozarkodina? snajdri with random occurrences of Pedavis latialatus, corresponds to the part of the "Icriodontid Zone" on Gotland, i.e. the uppermost part of the Lau Event. This incompleteness in record confirms sedimentary starvation in the shallow environment on the former volcanic elevation in this part of the Prague Basin.•

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The new shallow-water Bivalvia Janicula potens Community from the lower Gorstian carbonate platform influenced by the Svatý Jan Volcano activity in the Prague Basin, Bohemia is composed of 32 species [Slava sathon Kříž, 1985 (Slavidae); Cardiola donigala Kříž in Kříž & Serpagli, 1993, Cardiola signata Barrande, 1881, Cardiola aff. Geminans Barrande, 1881 (Cardiolidae); Dualina amina sp. nov. (Antipleuridae); Mila parvula Kříž in Kříž & Serpagli, 1993 (Stolidotidae); Algerina aff. algena Kříž, 2008, Tetinka costulifera sp. nov. (Spanilidae); Macrodesma enigma sp. nov. (Cyrtodontidae); Phthonia regularis (Barrande, 1881) (Mytilidae); Ambonychia volitans (Barrande, 1881), Amphicoelia pojetana sp. nov., Mytilarca parens (Barrande, 1881), Mytilarca sp. (Ambonychiidae); Molinicola bohemica sp. nov. (Pterineidae); Palaeopecten radvani sp. nov., Palaeopecten sp. (Leiopectinidae); Rhombopteria perunicola sp. nov. (Rhombopteriidae); Praeostrea bohemica Barrande, 1881 (Praeostreidae); Butovicella migrans (Barrande, 1881) (Butovicellidae); Mimerodonta phaseolus sp. nov., Janicula potens (Barrande, 1881), Goniophora tyri Liljedahl, 1984, Goniophora ascia sp. nov., Goniophora compta sp. nov., Goniophora solci sp. nov., Goniophora sp. (Modiomorphidae); Goniophorina nitidula sp. nov. (Goniophorinidae); Cymatonota prolata sp. nov., Cimitaria liscina sp. nov., Cimitaria cf. liscina sp. nov., Sanguinolites? drupa sp. nov. (Grammysiidae)]. In the paper one new genus (Janicula gen. nov.), and 15 new species are described. The Janicula potens Community occupied the environment of protected well-ventilated shallow-water flats, locally overgrown by algae, with carbonate sedimentation influenced by direct ash falls and the subsequent sedimentation of volcaniclastics by currents around the volcanic archipelago. It is accompanied by a rich benthos, especially crinoids, corals, gastropods, and brachiopods together with abundant trilobites, rostroconchids, common cephalopods, stromatoporids, relatively rare ostracods, tergomyans, polyplacophorids, worms, bryozoans, sponges, and algae. It is classified as a part of the Coral-Crinoid Community Group which in the Prague Basin, Bohemia includes the homologous and analogous late Homerian, Wenlock Coral-Leptaenid Community, Hircinisca-Ancillotoechia Community, and Septatrypa lissodermis-Cyrtia maior Community, the early Gorstian, Ludlow Atrypa fumosa Community, and the Coniproetus-Protocymostrophia Community. The Janicula potens Community from the Liščí Quarry locality near the Amerika gamekeeper’s lodge north of Karlštejn, Bohemia is the most diversified Bivalvia community in the Silurian of the Prague Basin. The lower Gorstian tuffaceous limestones, with more than 202 benthic and nektobenthic known species, represent the most fossiliferous Silurian level in the Prague Basin. The Janicula potens Community shows close palaeogeographic relationships with the upper Wenlock, Racine Formation reefs of Wisconsin and Illinois (North America), Silurian of Gotland and Dalarna (Sweden), Maine (Nort...

Excavation of Joachim Barrande's classic fossil locality of the "Aulacopleura shales" exposed on Na Černidlech Hill, near Loděnice reveals that most specimens were recovered from a 1.4 m interval exposed in "Barrande's pits". These are located at the eastern end of a 0.4 km trench dug in the mid 1800's to expose the interval along strike. Over an hundred bedding planes occur within the 1.4 m interval, and thousands of articulated trilobites have been collected at the site. Individual bed surfaces vary in the density, size, and taxonomic composition of the fossils contained. Some preserve a diverse benthic shelly fauna, others are almost exclusively dominated by the trilobite Aulacopleura koninckii, and a third variety is apparently barren of all shelly fossils. Isolated sclerites of A. koninckii are rare, and on almost all bedding surfaces exoskeletons are predominantly partially articulated and lack both alignment and sclerite fragmentation. The occurrence of A. koninckii conforms in many ways to the characteristics of a Type I trilobite lagerstätte of Brett et al. (2012). The presence of enrolled A. koninckii suggests that final burial may have resulted from relatively rapid obrution, although the condition of partial articulation indicates that many carcasses or exuviae partially disaggregated before burial. The mean size and density of A. koninckii specimens varies markedly among bedding planes, with some assemblages entirely comprised of juveniles, suggesting that notably dense trilobite clustering was not restricted only to reproductively mature individuals. The presence of multiple clusters of different mean specimen size partly accounts from the unusually comprehensive record of the articulated meraspid and holaspid ontogeny of this species at this locality. Limited bioturbation suggests a dysoxic substrate, and the olenimorphic form and distribution of A. koninckii, combined with a lack of encrustation or predation upon it, suggests that this species may have periodically bloomed in abundance at particular oxygen concentrations that largely excluded other skeletonized benthos. Some bedding plane assemblages might represent mass mortality events, perhaps as available oxygen passed below levels necessary to maintain the metabolism of A. koninckii. •