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The documentation of cuticular micro‐ornament is vital for the taxonomic assignment of palaeoscolecids: vermiform lower Palaeozoic ecdysozoans interpreted as stem‐group priapulans or early diverging panarthropods. This is due to the absence of the character‐rich proboscis and tail hooks in palaeoscolecid material not from Burgess Shale‐type Konservat‐Lagerstätten. Here, the cuticular micro‐ornamentation of palaeoscolecids from the upper Silurian (Ludlow) fauna of Leintwardine (Herefordshire, England), is described using scanning electron microscopy and reflectance transformation imaging. This material is taxonomically unstable because it was included in an effective wastebasket genus (Protoscolex) long before these imaging techniques were developed. The Leintwardine material is shown to be most closely comparable to a palaeoscolecid from the Darriwilian (Middle Ordovician) of the Builth–Llandrindod inlier, Powys, Wales, and is transferred accordingly to Radnorscolex Botting et al. as Radnorscolex latus (Bather). The Leintwardine fauna represents the uppermost stratigraphic occurrence of palaeoscolecids, constrained to the Saetograptus leintwardinensis Zone (lower Ludfordian), and the comparatively sparse Silurian palaeoscolecid record is subsequently discussed. It is hypothesized that palaeoscolecids may have become extinct during the mid‐Ludfordian Lau Event, the onset of which is recorded in the biozone immediately above the Leintwardine fauna (Bohemograptus Zone). Finally, the British palaeoscolecid fauna is summarized, including a new record from the Dapingian (Middle Ordovician) of Carmarthenshire, South Wales. [ABSTRACT FROM AUTHOR]

This contribution presents the record of an abundant assemblage of well-preserved, thallophytic noncalcified algae and of an epibiotic form that has been recognised as a putative graptolite from the upper Silurian (Ludlow, Gorstian-Ludfordian) of Podolia (western part of Ukraine). The sediments represent a shallow peritidal zone of the shelf. A new genus and species, Voronocladus dryganti, belonging to the Dasycladales Pascher, 1931, is established. Most of the specimens representing the algal thallus are overgrown by problematical epibiotic graptolites, described as Podoliagraptus algaeoides gen. et sp. nov. This phenomenon is explained as an epiphytic mode of life of the putative graptolite on algae, and is herein compared to recently known coexistences of algae with other organisms. The excellent state of preservation, and the abundance of studied Dasycladales algae and epibiotic problematics indicate that the investigated mudstone layer can be treated as a 'Konservat Lagerstätte' sensu Seilacher (1970). [ABSTRACT FROM AUTHOR]

Details of the endolymphatic structures are described for the first time in the headshields of the osteostracan genus Tremataspis from the Silurian of Estonia. Tiny platelets, here termed covering platelets, are located within the openings of the endolymphatic duct. The details of their shapes and arrangements differ among the four studied species. In Tremataspis schmidti Rohon and Tremataspis milleri Patten, the covering platelets are usually arranged in an oval or circular shape around the opening of the endolymphatic duct. These species can have smooth, flat covering platelets at the mouth of an irregularly funnel-shaped aperture in the dorsal shield; the funnel often has a posterior extension. In Tremataspis rohoni Robertson and Tremataspis mammillata Patten, a distinct circular arrangement of platelets does not occur; instead, their funnel was capped with a few (2â3) smooth, flat covering platelets. The funnel of T. milleri sometimes has a long postero-lateral extension, while that of T. mammillata can have a short extension; no extensions of the funnel have been observed in T. schmidti or T. rohoni. The diameter of the pores in the covering platelets is larger than that of the pores in the superficial layer of the headshield and much larger than the diameter of the pores in the porous fields (these are thin perforated bony septa subdividing the sensory canals horizontally into lower and upper parts). In T. milleri, the larger pores are located on the side of the covering platelets that is closer to the body midline. The discovered system of covering platelets possibly functioned as a sieve for allowing in suitable grains of material and preventing material that is too fine or too coarse, or not sufficiently dense, from entering the inner ear.

For years, the Ohesaare core section and its rich fossil assemblages have enticed researchers to suggest various ideas about Silurian stratigraphy in the East Baltic despite several sedimentary gaps occurring through the Ludlow interval in particular. One of the gaps has removed from the Ohesaare record the most important event in the Palaeozoic history of carbon isotopes â the Mid-Ludfordian Carbon Isotope Excursion (MLCIE), which is partly accompanied by the Lau biotic and oceanic events. In our research, we have performed a detailed distribution analysis of chitinozoans, conodonts, ostracodes and vertebrate microremains with the aim of documenting the evidence regarding the levels of certain environmental events largely preceding the MLCIE. For this purpose, the Torgu Formation was subdivided into five working units. The first results indicate a gap within the uppermost part of the Torgu Formation as a possible level for the missing MLCIE. In order to verify this, we compared the fossil distribution pattern in Ohesaare with that on Gotland (Sweden) and in Kurzeme (Latvia), including δ13C data from the Uddvide (Gotland) and Ventspils (Latvia) core sections. Both Baltic and Bohemian data show rather unanimously that the MLCIE is located below the Ozarkodinacrispa conodont Biozone. However, some reports from Gotland show peak values also in higher strata; occasional records of Oz. crispa from other places may cast some doubt on these findings and raise some ecostratigraphical concerns when discussing upper Ludfordian correlation.

In the field of urban morphology, different scholars have developed different approaches. The pioneering approaches are the procedural-typological approach of G. Caniggia and G.L. Maffei and the historico-evolutionary approach of M.R.G. Conzen, which are the focus of this paper. However, it is also worth mentioning J.W.R. Whitehand (1981), who integrated the analysis of changes to the built fabric with the study of the individuals and organizations involved in the various aspects of property development, users, planners, and architects. As well, Kropf (2009) named four distinct approaches – spatial analytical, configurational, process typological, and historico-geographical – for the purpose of determining more explicitly which aspects are included in the different approaches to urban morphology. Based on the theoretical approaches of the above-mentioned scholars, in the scope of this article, the architectural and planning dimensions of urban morphology will be discussed for Ludlow and Famagusta, which carry similar morphological characteristics on the planning level and different typological characteristics on the architectural level. Ludlow is a small market town in the south of Shropshire, England; it is a few miles east of the Welsh border. Famagusta, with its Old Town, is a small market town in the eastern part of Cyprus. This article explores urban morphology based on the two pioneering morphological approaches, and then it sets up a typo-morphological basis for Ludlow and Famagusta through an integrated approach. The belief is that such an integrated approach will drive future interventions, design, and planning policies towards their conservation.

Copyright of Estonian Journal of Earth Sciences is the property of Teaduste Akadeemia Kirjastus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Estonian Journal of Earth Sciences is the property of Teaduste Akadeemia Kirjastus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Three-dimensionally preserved fragments of the enigmatic organism Sandvikina, previously reported from the Silurian of Ireland, Scotland and Scandinavia, were recovered from the original Irish material that had revealed the problematic in thin sections. The new specimens derive from conodont residue and document silicified sectors of the distal part of the skeleton. Adifferent pattern characterizes the outer and inner walls, with an external net-like reticulated and an internal continuous and apparently imperforate framework, getting therefore a filter-like feeding system function highly improbable. [ABSTRACT FROM AUTHOR]

Silurian cyathaspidid heterostracans discovered from the East Baltic, North Timan, the Central and Southern Urals, and the Novaya Zemlya and Severnaya Zemlya archipelagoes in 1970‒2006 were studied. Earlier known taxa Archegonaspis schmidti (Geinitz, 1884), Archegonaspis lindstroemi Kiaer, 1932, Archegonaspis integra (Kunth, 1872) and Tolypelepis undulata Pander, 1856 were identified and described. Archegonaspis bimaris Novitskaya, 1970 is synonymized under A. schmidti (Geinitz) and Tolypelepis mielnikensis Dec, 2015 under Tolypelepis undulata Pander, 1856. Three new taxa, Archegonaspis bashkirica sp. nov., Cyathaspis alexanderi sp. nov. and Tolypelepis bedovensis sp. nov., were established, while two taxa, Archegonaspis lindstroemi? Kiaer and Tolypelepis sp. indet., remained in open nomenclature. The new subfamily Archegonaspidinae subfam. nov. was created. It is shown that besides details of the morphology of shields and plates, sculpture characteristics can be utilized in taxonomy. The material described complements the taxonomic content as well as the spatio-temporal distribution data of the species of the family Cyathaspididae.

Newly collected material reveals that the Silurian myodocope ostracods from the Holy Cross Mountains, Poland comprise ten species (one new to science) belonging to four families: Bolbozoidae, Entomozoidae, Rhomboentomozoidae, and Cypridinidae. Biostratigraphic control using graptolites indicates that all three Polish outcrops investigated are of about the same chronostratigraphical level: middle Gorstian, lower Ludlow. The new occurrences in Poland extend the known distribution of several species and reinforce data that show many Silurian myodocope species with wide dispersal. Our new observations on the Holy Cross Mountains material confirm that the occurrences of Silurian myodocopes are mostly associated with pelagic animals and with rocks ranging from mudstone, siltstone or shale deposited in open- or deep-shelf marine settings. The cosmopolitan distribution of these ostracods, coupled with their facies and faunal associations, supports the notion of an ostracod (myodocope) ecological shift from benthic to planktonic habitats during the late Wenlock and Ludlow.

Ludfordian strata exposed in the Burgen outlier in eastern Gotland, Sweden record a time of initial faunal recovery after a global environmental perturbation manifested in the Ludfordian Carbon Isotope Excursion (LCIE). Vertebrate microfossils in the collection of the late Lennart Jeppsson, hosted at the Swedish Museum of Natural History, hold the key to reconstruct the dynamics of faunal immigration and diversification during the decline of the LCIE, but the stratigraphic relationships of the strata have been debated. Historically, they had been placed in the Burgsvik Formation, which included the Burgsvik Sandstone and the Burgsvik Oolite members. We revise the fauna in the Jeppsson collection and characterize key outcrops of Burgen and Kapellet. The former Burgsvik Oolite Member is here revised as the Burgen Oolite Formation. In the Burgen outlier, back-shoal facies of this formation are represented and their position in the Ozarkodina snajdri Biozone is supported. The shallow-marine position compared to the coeval strata in southern Gotland is reflected in the higher δ13Ccarb values, reaching +9.2‰. The back-shoal succession includes high-diversity metazoan reefs, which indicate a complete recovery of the carbonate producers as the LCIE declined. The impoverishment of conodonts associated with the LCIE in southern Gotland might be a product of facies preferences, as the diverse environments in the outlier yielded all 21 species known from the formation. Fish diversity also returned to normal levels as the LCIE declined, with a minimum of nine species. In line with previous reports, thelodont scales appear to dominate samples from the Burgen outlier. [ABSTRACT FROM AUTHOR]

The article presents the results of a study of Wenlock-Ludlow boundary sediments in the river Padimeytyvis basin at Chernov uplift using paleontological, lithological and chemostratic methods. The results of paleontological studies allowed attributing to the Wenlock the carbonate stratum of the upper part of the section along the stream Bezymjannyi and establishing Wenlock-Ludlow boundary only in the section of the river Padimeytyvis. The results of studying the isotope δ13Ccarb. in Wenlock-Ludlow boundary sediments are also presented. In the upper part of the section along the stream Bezymyanny a positive C-isotopic shift of the curve which possibly marks the late Wenlock global biotic event of Mulde was observed. Keywords: Ludlow, Wenlock, conodonts, brachiopods, Arctic region, Timan-Northern Ural region, isotope δ13Ccarb. [ABSTRACT FROM AUTHOR]

The Ludlow epoch of the Silurian period was a time of significant geobiological perturbations, the most significant being the mid-Ludfordian Lau Event and associated huge positive carbon isotopic excursion. On the other hand, the impact of the Lau Event on ecosystems is far from understood, with the majority of studies being concentrated on conodonts, graptolites, and brachiopods. Therefore, here we present the high-resolution Gorstian to mid-Ludfordian Baubliai-2 core section record of the phytoplankton (acritarch and green algae) change from the deep shelfal facies belt of the Silurian Baltic Sedimentary Basin. Seven distinct phytoplankton assemblages are distinguished. The general feature of the assemblage change is an overarching trend toward higher relative abundances of the green algae disaster taxon Leiosphaeridia spp., which peaked during the Lau Event. The absolute abundance variability of the various components of the plankton including the hyper-abundant Leiosphaeridia spp. and Tasmanites spp. revealed the presence of consistent 0.93 Ma cyclicity. The diversity of phytoplankton is directly correlated with graptolite species diversity, which suggests common driving mechanisms of evolution for different components of the plankton community. The recurrence and joint recurrence plots and recurrence quantification analysis revealed a coordinated evolution of phytoplankton and graptolite diversities. The Lau Event interval stood out as a distinct coordinated low diversity state in both phytoplankton and in graptolites. Similar anomalous community states were previously detected in benthic communities (brachiopods), and in communities of pelagic predators (conodonts). Therefore, the current evidence suggests that the Lau Event had a significant impact across the whole range of communities and ecosystems. • The relative abundance of a "disaster taxon" Leiosphaeridia spp. increased with time during Ludlow, peaking during Lau Event. • The dynamics of absolute abundance of different plankton groups was driven by 0.93 Ma cyclicity. • The dynamics of diversity in phytoplankton and graptolites were directly correlated. • Lau Event represented coordinated low phytoplankton and graptolite diversity state, anomalous in Ludlow Epoch context. [ABSTRACT FROM AUTHOR]

The conodont biozonation for the Silurian succession in the Appalachian Basin was established by C.T. Helfrich nearly half a century ago. Herein, we re-examined and updated the taxonomy of the conodont fauna and the consequent biozonation of the upper Rose Hill, Mifflintown, Wills Creek, and lower Tonoloway formations in the east-central Appalachian Basin. While these strata span the upper Telychian Stage (Llandovery Series) to the upper Pridoli Series, a major stratigraphic gap representing most of the Ludlow Series (from the lower part of the Gorstian to the upper part of the Ludfordian stages) was identified. The new conodont biozonation consists of: the Pterospathodus amorphognathoides amorphognathoides Zonal Group, an Unzoned Interval of the Sheinwoodian Stage, the Kockelella walliseri Zonal Group, the Ozarkodina bicornuta Zone, an Unzoned Interval of the Homerian Stage, the Ozarkodina bohemica Interval Zone, the Ozarkodina crispa Zone, and the Ozarkodina eosteinhornensis sensu lato Interval Zone. This refined biozonation permits enhanced global correlation of the Silurian within the east-central Appalachian Basin. [ABSTRACT FROM AUTHOR]

The coquinoid beds from the middle part of the Los Espejos Formation at the Poblete creek section (Talacasto Creek) yielded abundant conodonts. The genus Kockelella (Walliser) represents the most relevant biostratigraphical genus in this conodont fauna. The co‐occurrence of Kockelella maenniki Serpagli and Corradini, Kockelellavariabilisichnusae Serpagli and Corradini, K. variabilis Walliser, Kockelella ortus sardoa (Serpagli & Corradini), and Kockelella ortus absidata (Barrick & Klapper) allow us to record for the first time the Polygnathoides siluricus Zone in South America, which suggests the Ludfordian Stage (late Ludlow). We also propose an accurate correlation of the Los Espejos Formation with the lower Ludfordian deposits from the Carnic Alps, Sardinia, Morocco, Czech Republic, Gotland, and North America. [ABSTRACT FROM AUTHOR]

Copyright of Estonian Journal of Earth Sciences is the property of Teaduste Akadeemia Kirjastus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Newly collected material reveals that the Silurian myodocope ostracods from the Holy Cross Mountains, Poland comprise ten species (one new to science) belonging to four families: Bolbozoidae, Entomozoidae, Rhomboentomozoidae, and Cypridinidae. Biostratigraphic control using graptolites indicates that all three Polish outcrops investigated are of about the same chronostratigraphical level: middle Gorstian, lower Ludlow. The new occurrences in Poland extend the known distribution of several species and reinforce data that show many Silurian myodocope species with wide dispersal. Our new observations on the Holy Cross Mountains material confirm that the occurrences of Silurian myodocopes are mostly associated with pelagic animals and with rocks ranging from mudstone, siltstone or shale deposited in open- or deep-shelf marine settings. The cosmopolitan distribution of these ostracods, coupled with their facies and faunal associations, supports the notion of an ostracod (myodocope) ecological shift from benthic to planktonic habitats during the late Wenlock and Ludlow. [ABSTRACT FROM AUTHOR]

A fundamental principle of all truth-conditional approaches to semantics is that the meanings of sentences of natural language can be compositionally specified in terms of truth conditions, where the meanings of the sentences' parts (words/lexical items) are specified in terms of the contribution they make to such conditions their host sentences possess. Thus, meanings of words fit the meanings of sentences at least to the extent that the stability of what a sentence might mean as specified in a theory is in accord with the stability of what a word might mean as similarly specified. In this paper, I shall be concerned with Ludlow's (2014) idea that, in fact, there need be no such sympathy between words and sentences. He proposes that we can square what he calls a dynamic lexicon, where word meaning is not stable at all, with a traditional truth-conditional approach of the kind indicated, where sentence meaning is delivered via 'absolute truth conditions'. I share Ludlow's aspiration to accommodate dynamic features of word meaning with a truth conditional approach, but not his belief that the marriage is an easy deal. Thus, I shall present a problem for Ludlow's position and show how resolving this problem leads to an alternative picture of how the meaning of a sentence may be truth-conditionally specified with all relevant dynamic features of the lexicon retained. [ABSTRACT FROM AUTHOR]

The regional zonation of the Wenlock–Ludlow boundary is established for the Prague Synform using refined data from updated conodont records. The following conodont zones have been recognized in the Prague Synform: the Ozarkodina sagitta sagitta Zone, the Ozarkodina bohemica Interval Zone, the Kockelella crassa Zone, the Kockelella variabilis variabilis Interval Zone and the Ancoradella ploeckensis Zone. The Ozarkodina bohemica longa and Kockelella ortus absidata zones are used herein at subzonal level only because the entries of index taxa cannot be precisely detected. The Bohemian conodont zonal scale is correlated with the recently proposed standardized zonation. The established conodont zones are tentatively correlated with global graptolite zonation and matched against generalized eustatic and carbon isotope curves.

This is the second part of an examination of one particular aspect of the planning process in new towns of the early medieval period in England which were set out on a rectilinear module. In all these planned towns, the way in which burgages were laid out at the corners of streets meeting at right angles will have always been problematical. Four towns (excluding Bridgnorth, discussed earlier), ranging in date from the late ninth to the late twelfth century, are examined to illustrate one particular way in which these spatial problems were resolved. Deductions are made from this evidence concerning the contemporaneity or otherwise of streets and burgage systems, seen as inter-functional ensembles. These observations and deductions generate new historical narratives relating to both the morphogenetic development of the towns studied and, in some cases, the wider course of the development of urbanism in general. [ABSTRACT FROM PUBLISHER]

Nine altered volcanic ash samples from the shoal and lagoonal sediments of the Rootsiküla Stage (Wenlock–Ludlow boundary interval, Estonia) were analysed, compared and correlated with five samples of deep sea environments from Latvia. Volcanic ash correlations indicate that the Wenlock–Ludlow boundary correlates with the boundary of the Viita and Kuusnõmme beds, i.e., it is significantly lower than proposed earlier. The distribution of chitinozoans supports this new correlation. Geochemical data indicate subalkaline source magma of volcanic ashes with potassium dominating over sodium.

The distribution of chitinozoans in the East Baltic Ludlow sequences was studied in the Ohesaare, Ventspils, Pavilosta, and Dubovskoye drill core sections. The Angochitina elongata, Eisenackitina lagenomorpha, and Eisenackitina barrandei biozones were described and correlated with the regional stratigraphical units, as well as with conodont and vertebrate biozones in the Ohesaare core.

Paleofavosites cf. collatatus Klaamann occurs abundantly in marls and bioherms of the Muksha Member of the Bagovitsa Formation (Upper Silurian, Ludlow). The morphological variation of this species identified in different localities is analysed. The biometrical data show that there is no substantial variation among specimens from different localities except that corallum shapes are taller in marls than in bioherms and corallites are slightly smaller in specimens from bioherms. The irregular growth of coralla is common to this area.

The distribution of chitinozoans in the Wenlock–Ludlow boundary beds was studied in five drill core sections of the East Baltic. It was established that most of the typical Wenlock chitinozoan species became extinct in the uppermost part of the Jaagarahu Stage. In the lower part of the Rootsiküla Stage the Sphaerochitina lycoperdoides Biozone was identified for the first time. The Conochitina postarmillata and Ancyrochitina desmea biozones were established in the Dubysa Formation of the Paadla Stage in the Ventspils and Pavilosta cores and in the Gorstian Stage of the Gussev-1 core. Two stratigraphically important new species, Rhabdochitina sera and Conochitina postarmillata, were described, and Eisenackitina lagena (Eisenack) was redescribed.

A collection of low-grade metamorphosed rocks from Lvchun, Yunnan, Southwest China was found to contain a variety of highly mature microfossils comprising cryptospores, trilete spores, and dispersed plant fragments (tubular structures) as well as a small number of marine palynomorphs (acritarchs and scolecodonts). Infrared microscopic examination enabled the recognition and description of 38 species. Based on its correlation with previously established palynozonations and independent age evidence from acritarchs and graptolites, the palynomorph assemblage from Lvchun is attributed to the early Ludlow age. This new age constraint suggests that at least the upper level of these presumably Llandovery rocks in Lvchun belongs to the early Ludlow age. The palynomorph assemblage of Lvchun from Indo-China terrane shares many taxonomic similarities with coeval findings from Tunisia and Saudi Arabia (i.e., southern Gondwana), hence reflecting the early geographical proximity of the two palaeocontinents. The increasing quantity and diversity of trilete spores point to the rapid evolution of early vascular plants in Indo-China terrane during the early Ludlow. [ABSTRACT FROM AUTHOR]

The section of the Upper Silurian on the Western slope of the Subpolar Urals is located on the Kozhym River bank. This paper presents the results of studying of the geological structure of the upper Ludlowian section and data on lithology, geochemistry, and environment reconstructions of carbonate-terrigenous deposits of the late Ludlow and at the boundary of the Ludlow and Pridoli. [ABSTRACT FROM AUTHOR]

The regional zonation of the Wenlock-Ludlow boundary is established for the Prague Synform using refined data from updated conodont records. The following conodont zones have been recognized in the Prague Synform: the Ozarkodina sagitta sagitta Zone, the Ozarkodina bohemica Interval Zone, the Kockelella crassa Zone, the Kockelella variabilis variabilis Interval Zone and the Ancoradella ploeckensis Zone. The Ozarkodina bohemica longa and Kockelella ortus absidata zones are used herein at subzonal level only because the entries of index taxa cannot be precisely detected. The Bohemian conodont zonal scale is correlated with the recently proposed standardized zonation. The established conodont zones are tentatively correlated with global graptolite zonation and matched against generalized eustatic and carbon isotope curves. [ABSTRACT FROM AUTHOR]

Numerous tiny curved to slightly sinuous subvertical tubicolous bioclaustrations occur in stromatoporoids from the Katri cliff biostrome. About 77.8% (N = 18) of Katri biostrome stromatoporoids contained worm endobionts.Chaetosalpinx sibiriensisoccurs inPlectostroma scaniense,Petridiostroma convictumand “Stromatopora” bekkeri/Parallelostroma typicum.Helicosalpinx concoenatusoccurs inP. scaniense. The distribution ofC. sibiriensisis thus not restricted to tabulate corals because it also occurs in stromatoporoids.H. concoenatuswas not endemic to North America as it also occurs in the Late Silurian of Baltica. [ABSTRACT FROM AUTHOR]

Abstract: A well-preserved isolated graptolite Prolinograptus packhami Rickards and Wright, 1997, well known from Australia, is described for the first time in Europe. The genus has now been recognized in three continents (Australia, Europe and North America). The Australian P. packhami occurs in the Neocucullograptus inexpectatus/Neocucullograptus kozlowskii biozonal interval, while the form from the Mielnik IG-1 core, Poland, appears earlier, in the Bohemograptus praecornutus Biozone. Prolinograptus, of unclear origin, is one of the least-known genera of the subfamily Linograptinae. P. packhami, along with Neodiversograptus palmeri and Prolinograptus orangensis, form a group of very diminutive specimens, with slender stipes and thecal apertures showing varying degrees of eversion. Scanning electron microscope examination revealed the presence of some micro-ornamentation on the rhabdosome surface of the Polish Prolinograptus, similar to that known in retiolitids (Retiolitidae). [Copyright &y& Elsevier]

Silurian environmental changes during approximately 15 million years of retiolitid (Graptolithina) evolution resulted in the progressive reduction and possibly disappearance of their rhabdosome. A strong decrease in retiolitid colony size is also observed. This results from an increase in the sicula size and a decrease in the number of thecae during their evolution.PlectodinemagraptusgracilisKozłowska-Dawidziuk, 1995 from thehemiaversus/aversusandleintwardinensisbiozones, lower Ludfordian of the East European Platform of Poland, is the youngest known retiolitid. It has a very small rhabdosome comprising a very simple ancora umbrella with reduced lateral lists, free nema and ventral walls of two parallel rods with prominent loops per theca. The ancora sleeve seems to be extremely reduced. The rhabdosome with two pairs of thecae reaches about 2 mm in length. It is parallel sided, as in some larger Ludlow forms, e.g.Plectograptus(Moberg & Törnquist, 1909) andSemiplectograptusKozłowska-Dawidziuk, 1995.P. gracilisis a clear example of the latest stage of the reduction in the retiolitid colony and the last known form to appear before their extinction, which coincided with theleintwardinensisevent. [ABSTRACT FROM AUTHOR]

The facies development through the stratigraphical interval of the Silurian (late Ludlow) Lau Event and the associated major δC record excursion have been studied in the Prague Basin. The investigated sections consist of temperate-water carbonates (Kopanina Formation) that were deposited in shallow as well as deeper parts of the basin. In both areas, the facies evolution reflects a major shallowing of sea-level during the early part of the event, which resulted in weathering (karstification) and erosion in the shallower parts of the basin, leading to stratigraphic gaps there. Paleokarst features and dolomitization are associated with these strata in the vicinity of Prague, where the δC record displays a strong diagenetic overprint and palynomorphs are very poorly preserved. A transition from deep-water shale to subtidal, thick-bedded limestone facies in the deeper parts of the basin, close to Kosov, signals the same sea-level drop, indicating that it was basin-wide. Detailed lithologic descriptions for the studied sections are provided and the development in the Prague Basin is compared with the coeval succession on Gotland, Sweden, which was located in the tropical realm at this times. [ABSTRACT FROM AUTHOR]

Abstract: An unexpected new form of Bohemograptus with unusual morphological structure has been found in the upper part of the Bohemograptus praecornutus Biozone, Upper Ludlow of the Mielnik borehole, Poland. Bohemograptus papilio sp. nov. has the characteristic rhabdosome for Bohemograptus, in addition to extraordinary paired latero-dorsal additions, not comparable to any processes typical for Bohemograptus thecal openings. The new structure, a patagium, is located in the proximal part of the rhabdosome, and is built from main rods dividing repeatedly into thinner lists with significant remnants of membranes spread between them. Another new structure is the virgellarium, a membranous addition to the virgella. Membranes of the patagium and virgellarium are not built from microfusellar tissue as additions in other bohemograptids. It is suggested that the membranous additions were orientation devices, constructed to retard the sinking of the colony in the water column. [Copyright &y& Elsevier]