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Probable ancestral type of actinodont hinge in the Ordovician bivalve Pseudocyrtodonta Pfab, 1934  [PDF]
Steinová M
Bulletin of Geosciences , 2012, DOI: 10.3140/bull.geosci.1330
Abstract: The type species of Pseudocyrtodonta, P. ala and other two species P. incola, P. obtusa are known from the Middle and Upper Ordovician of the Prague Basin, Bohemia. Because of the actinodont type of the hinge, Pseudocyrtodonta is excluded from the subclass Protobranchia and is transferred to the Autobranchia, family Cycloconchidae. The family Pseudocyrtodontidae is considered invalid. Early and Middle Ordovician Cycloconchidae were highly diversified, containing 24 genera. Their diversity suddenly decreased during the Upper Ordovician to three genera only. The hinge of Pseudocyrtodonta could be considered morphologically close to the ancestral type of the hinge of the actinodonts. A complete species list of Ordovician actinodonts, including schematic figures of their hinge for the most important genera is presented. Pseudocyrtodonta was most probably an active burrower.
Heterotopy and heterochrony in the palaeotaxodont bivalve Natasia boliviensis (Babin and Branisa) from the Early Ordovician of northwestern Argentina
Sánchez,Teresa M.;
Ameghiniana , 2009,
Abstract: in the last few years several contributions concerning heterochronic processes have been produced, but only few papers dealing on heterotopy have been published. material of natasia boliviensis (babin and branisa, 1987) from the early ordovician of northwestern argentina includes specimens at different growth stages, from smaller, juvenile individuals with taxodont dentition, to larger adult shells displaying actinodont dentition. ontogenetic development of dentition is tentatively interpreted as resulting from heterotopic changes from an unknown praenuculid ancestor, whereas changes in shell outline could be explained by mean of heterochrony.
The trend from 1934 to 2001 of metal concentrations in bivalve shells (Unio pictorum) from two small lakes: Lake Levico and Lake Caldonazzo (Trento Province, Northern Italy)  [cached]
Oscar RAVERA,Pier Renato TRINCHERINI,Gian Maria BEONE,Bruno MAIOLINI
Journal of Limnology , 2005, DOI: 10.4081/jlimnol.2005.113
Abstract: This research follows the variations in calcium and 14 trace metal concentrations in mussel shells (Unio pictorum) from two lakes with different trophic levels, Lake Levico and Lake Caldonazzo (Northern Italy) from 1934 to 2001. During this period, the concentration of 11 trace metals increased and that of 3 decreased in the shells from Lake Levico, while the shells from Lake Caldonazzo showed an increase in the concentration of 6 metals, a decrease in 6 and no variation in 2. In both the lakes the concentration increases were far greater than the concentration decreases. In 1934 as well as in 2001 the metal concentrations in the shells from Lake Levico were higher than those from Lake Caldonazzo, although the concentrations of the most abundant metals in the filtered water of the latter lake were higher than those found in the water from Lake Levico. This apparent anomaly, also observed in an earlier study on the same species in 12 lakes, seems to be the combined effect of several causes (e.g. trophic level of the environment, metal concentration in the food), among which metal speciation in the water is probably one of the most important.
Nacre in Molluscs from the Ordovician of the Midwestern United States  [PDF]
Michael J. Vendrasco,Antonio Checa,William P. Heimbrock,Steven D.J. Baumann
Geosciences , 2013, DOI: 10.3390/geosciences3010001
Abstract: Nacre was previously thought to be primitive in the Mollusca, but no convincing Cambrian examples are known. This aragonitic microstructure with crystal tablets that grow within an organic framework is thought to be the strongest, most fracture-resistant type of shell microstructure. Fossils described herein from the Ordovician of Iowa, Indiana, and Ohio provide supporting evidence for the hypothesis that sometime between the middle Cambrian and late Ordovician, nacre originated in cephalopod, bivalve, and possibly gastropod lineages. The correlation of independent origins of fracture-resistant nacre with increasing shell-crushing abilities of predators during the Cambrian-Ordovician suggests an early pulse in the evolutionary arms race between predators and molluscan prey.
Khor Al-Odaid Conflict Between Kingdom of Saudi Arabia and Abu-Dhabi in (1934-1952) and British Attitude Towards it (1934 – 1952)  [cached]
Husain Altemimi
Historical Kan Periodical , 2012,
Abstract: (1934- 1952) 1934 1952 . . status quo .
Menger 1934 revisited  [PDF]
Ole Peters
Quantitative Finance , 2011,
Abstract: Karl Menger's 1934 paper on the St. Petersburg paradox contains mathematical errors that invalidate his conclusion that unbounded utility functions, specifically Bernoulli's logarithmic utility, fail to resolve modified versions of the St. Petersburg paradox.
BIVALVE FEEDING — HOW AND WHAT THEY EAT?  [PDF]
Jasna Arapov,Daria Ezgeta-Bali?,Melita Peharda,?ivana Nin?evi? Gladan
Ribarstvo : Croatian Journal of Fisheries , 2010,
Abstract: Based on the mechanism of food collection, bivalves can be suspension–feeders or deposit–feeders, or even utilize both feeding methods. Although some authors describe bivalve feeding as “automatized” process, recent studies show that some bivalves species have ability to regulate filtration and select% particles based on their size, shape, nutritive value or chemical component on the surface of the particle. Several recent studies also showed that phytoplankton is not necessary primary food source for bivalves and pointed out the importance of other food sources such as bacteria, detritus and even zooplankton, including bivalve larvae. Ingestion of bivalve larvae indicates that adult bivalve grazing influence different life stages of these organisms and could have impact on bivalve stocks. Due to these process bivalves have great influence in energy and nutrient flux between benthic and pelagic communities, what makes them important part of marine food webs. This paper gives us the overview of current literature and understanding of bivalve feeding mechanisms, particle select%ion and food sources.
Ordovician timescale in Estonia: recent developments
N?lvak, Jaak,Hints, Olle,M?nnik, Peep
Proceedings of the Estonian Academy of Sciences. Geology = Teaduste Akadeemia toimetised. , 2006,
Abstract: Over 150 years of progress in the Ordovician geology and stratigraphy of Estonia has resulted in one of the most precise Ordovician timescales in the world. In this paper, an up-to-date version of the Ordovician timescale of Estonia is provided. Recent developments in graptolite, chitinozoan, and conodont biostratigraphy, and the correlation with the global standard are briefly commented upon. Application of the regional subseries rank is discussed and two new names are proposed: “Vinni” for the upper subseries of the Viru Series, and “Atla” for the upper subseries of the Harju Series.
Ordovician conodont diversity in the northern Baltic  [PDF]
Peep M?nnik,Viive Viira
Estonian Journal of Earth Sciences , 2012, DOI: 10.3176/earth.2012.1.01
Abstract: The diversity data presented in this paper are based on recently revised collections of conodonts from outcrops (northern Estonia) and core sections of Estonia and western and northern Latvia. Based on variations in the abundance of taxa, four intervals with different general trends in diversity changes can be recognized in the Ordovician part of the succession: (1) the proavus–crassus zones and (2) crassus–anserinus zones, both intervals forming quite distinct diversity cycles; (3) the variabilis–ventilatus zones, characterized in general by stable diversity values, and (4) the ventilatus Zone–the topmost Ordovician, with a steady increase in diversity up to the ordovicicus Zone, followed by a decline during the End-Ordovician Extinction Event. Diversity was lowest in the earliest and latest Ordovician but reached maximum values at the end of the Early Ordovician radiation of conodonts, in the middle and upper Darriwilian, and just before the start of the End-Ordovician Extinction Event. Four supersequences (transgressive–regressive cycles) are proposed here for the northern Baltic Ordovician succession. The diversity changes recognized in the conodont succession demonstrate general correlation with these supersequences: boundaries between supersequences are characterized by low diversity values; diversity increases more or less rapidly in the lower, transgressive parts of the supersequences and decreases in their upper parts.
Uppermost Ordovician bivalves from the Prague Basin (Hirnantian, Perunica, Bohemia)  [PDF]
K?í? J,Steinová M
Bulletin of Geosciences , 2009, DOI: 10.3140/bull.geosci.1141
Abstract: Twelve species (four new) and 9 genera of bivalves are described from the uppermost Hirnantian, Upper Ordovician of the Prague Basin, Bohemia: Praenucula dispar (Barrande, 1881), Praenucula abrupta sp. nov., Sluha kosoviensis (Barrande, 1881), Nuculites aff. planulatus Conrad, 1841, Myoplusia contrastans (Barrande, 1881), Myoplusia obtusa (Barrande, 1881), Myoplusia sp., Metapalaeoneilo dromon sp. nov., Praeleda compar (Barrande, 1881), Mytilarca mareki sp. nov., Modiolopsis pragensis sp. nov., and ?Sphenolium cf. parallelum Ulrich, 1894. From the coarse, storm generated sandstones representing the additional regressive event, when the shelf was channelled, and coarse material transported from the shore in the late Hirnantian, the low diversified, almost monospecific Modiolopsis pragensis Community, of the Modiolopsis Community Group, was described. It indicates restricted living conditions. 11 bivalve species form, together with 25 species of brachiopods, 5 species of gastropods, and undescribed conulariids, hexactinellids, trepostomate bryozoans, annelids, hyolithids, orthocone nautiloids, rare ostracods, phyllocarids, blastoids, cystoids, crinoids, dendroids, graptolites, and chlorophytes (receptaculitids) the redefined Hirnantia sagittifera–Sluha kosoviensis Community. It represents the most diversified community of the Hirnantia Community Group known in the World. We suppose that the Hirnantia sagittifera–Sluha kosoviensis Community occupied the well-ventilated environment of the soft bottom carbonate silts with high organic content. The community was most probably autochthonous, with minimal transport as is indicated by the common preservation of shells with conjoined valves (articulate brachiopods, semi-infaunal bivalve Mytilarca mareki, and infaunal bivalves). The bivalves Mytilarca mareki and Metapalaeoneilo dromon sp. nov., Nuculites aff. planulatus, and ?Sphenolium cf. parallelum may have originated in the Baltica carbonate platforms and the equatorial regions of Avalonia and Laurentia and support the ideas about the position of the Kosov Province in the temperate-to-subtropical zone (between 30° to 45° S). For the analogous and homologous communities we described the Hirnantia Community Group as a substitute for the term “Hirnantia fauna”. The Hirnantia Community Group was most probably extending from the circumpolar sphere into the temperate to tropical zones in proximity to the carbonate platforms. In Bohemia and elsewhere it occurs just a few metres below the Ordovician-Silurian boundary and represents the evidence of the environmental re
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