• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 7
  • 5
  • Tagged with
  • 12
  • 12
  • 6
  • 6
  • 6
  • 6
  • 4
  • 4
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Hyoliti Barrandienu / Hyoliths of the Barrandian area

Valent, Martin January 2011 (has links)
of Mgr. Martin Valent doctoral thesis Hyoliths of the Barrandian Area The submitted Ph.D. thesis summarizes recent information on comparatively poorly known group of invertebrates - the hyoliths. The first part of the thesis is composed by six main chapters focussed in detail on various aspects of hyoliths; major characteristics and ecology of hyoliths, progress in systematic of hyoliths, principles of hyolith classification, stratigraphical and palaeogeographical distribution of hyoliths, hyoliths within the Bohemian Massif and morphology of hyoliths. Up-to-date information has been included in all chapters. New data were published in five author's papers on hyolith colour patterns, systematics of hyoliths, pattern of palaeogeographic distribution and palaeoecologic interactions between hyoliths and various elements of the Cambrian invertebrate fauna. Short appendage consists of the Czech-English-Chinese terminological dictionary, simplifying study of Chinese literature.
2

Ontogenetický vývoj eokrinoidních ostnokožců kambria barrandienské oblasti / Ontogenetic development of Cambrian eocrinoid echinoderms of the Barrandian area

Nohejlová, Martina January 2013 (has links)
This diploma thesis presents the first study focused on the ontogenetic development of eocrinoid echinoderms in the Czech Republic. Parsley's work (2012) on ontogeny of the genus Gogia from south China is the model study. The aim of this thesis is a comparable study of ontogeny of eocrinoid echinoderms from Cambrian of the Barrandian area. Akadocrinus jani Prokop, 1962 was studied. Using detailed morphological description and measurement of various parameters, three different ontogenetic stages have been established: juvenile ontogenetic stage, mature ontogenetic stage and gerontic ontogenetic stage. Thecal height is the deciding factor for the determination of the specific ontogenetic stage. Further, during ontogeny of this species some trends in changes in the size of body parts are observed (e.g., changes in the diameter of thecal plates). In-depth study of morphological details showed that the originally distinguished two species, Akadocrinus jani Prokop, 1962 and Akadocrinus nuncius Prokop, 1962, represent one species only. Keywords: eocrinoid echinoderms, Akadocrinus jani, ontogeny.
3

Linguliform Brachiopods from the Middle Cambrian ‘Thick’ Stephen Formation at Odaray Mountain, Canadian Rocky Mountains

Saxén, Sara January 2015 (has links)
The linguliform brachiopod fauna from the Stephen Formation have long been thought to be very species poor and only consist of a few genera, but new discoveries from lime-stone beds in the “thick” Stephen Formation shows that this is not the case. The species described herein, Kyrshabaktella cf. tatjanae and Ceratreta hansi sp. nov., are two new additions to described species and genera of the area.The specimens come from a 0.6 meters thick limestone bed, approximately 17 meter above the base of the formation in the Canadian Rocky Mountains, British Columbia, Yoho National Park a few kilometers SSE from Odaray Mountain. The specimens where retained from the rock by dissolution in diluted formic acid for a few days and later coated with a palladium-gold alloy and photographed under a Scanning Electron Microscope (SEM).In addition to the widen knowledge that these specimens of K. cf. tatjanae and C. hansi brings to the paleoecology of the area the two species also expands the knowledge of their families and genera. The coarse filae ornamentation on the exterior shell of K. cf. tatjanae requires the revision of the diagnosis of the family Kyrshabaktellidae and the discovery of the new species C. hansi expands the stratigraphic range of the genus Ceratreta to the middle Cambrian. / Detta arbete behandlar arterna Kyrshabaktella cf. tatjanae och Ceratreta hansi sp. nov. från den ’tjocka’ Stephenformationen. Tidigare har området ansetts vara väldigt art- och släktfattigt på linguliforma brachiopoder. Nya fynd av Caron m.fl. (2010, 2014) visar på att så inte är fallet, och de fynd som behandlas här styrker den bilden. Fynden kommer från ett kalkstenslager beläget ca 17 meter upp i sekvensen på den ’tjocka’ Stephenformationen. Lagret har visat sig vara väldigt rikt på fossil. Med hjälp av dessa exemplar av K. cf. tatjanae har diagnosen av familjen Kyrshabaktellidae kunnat ändras, från att inte ha haft några utsmyckningar alls på de vuxna skalen till att kunna ha bland annat grovt koncentriska ornament (s.k. filae). Detta arbete och dessa nya fynd ska sprida ytterligare ljus över området. Förhoppningen är att denna ska hjälpa till att ge ny kunskap om områdets paleoekologi samt arterna och släktenas geografiska utbredning.Fossilen har separerats från kalkstenen genom att låta stufferna dra i utspädd myrsyra några dagar, tills kalken är upplöst. Fossilen har belagts med en palladium-guld legering och fotograferats med hjälp av ett svepelektronmikroskop (SEM).Syftet med arbetet är att göra en taxonomisk beskrivning av nya exemplar av brachiopodfossil från Stephenformationen.
4

Ontogeneze vybraných taxonů trilobitů a agnostoidů ze středního kambria barrandienské oblasti / Ontogeny of selected taxa of middle Cambrian trilobites and agnostoids of the Barrandian area

Laibl, Lukáš January 2017 (has links)
This thesis deals with the ontogeny of trilobites and agnostids from the Cambrian of the Skryje-Týřovice and Příbram-Jince basins (Barrandian area, Bohemian Massif). Thesis is presented as a compilation of four papers that were published in scientific peer-reviewed journals. The introduction of the thesis serves as a general overview of the trilobite post- embryonic development and connects all published papers together. All four papers presented here are focussed on modern description of the post-embryonic development of Sao hirsuta, Ptychopariida sp. A, Ptychopariida sp. B, Ptychopariida sp. C, Ellipsocephalus hoffi, Ellipsocephalus polytomus, Hydrocephalus carens and Ecca- paradoxides pusillus. In addition, a discussion about the life-history strategies of early developmental trilobite stages is presented. It has been suggested that Sao hirsuta and Ptychopariida sp. A had benthic protaspides and that the early ontogenetic stages of Ptychopariida sp. B, Eccaparadoxides pusillus and Hydrocephalus carens were likely lecithortophic. Consequently, it has been documented that species with benthic protaspides show a strongly restricted geographic distribution and that lecithotrophic taxa seem to be associated with higher latitude areas. The developmental patterns of Ellipsocephalus hoffi and...
5

SCF ve spodním paleozoiku barrandienské oblasti / SCF in Lower Palaeozoic sediments of the Barrandian area

Kovář, Vojtěch January 2020 (has links)
1 Abstract In recent years, the term small carbonaceous fossils (SCFs) has been established to accomodate fragile organic-walled fossils of micro- to mesoscopic size that are usually extracted by means of the 'low-manipulation HF extraction' method. This method has so far only been utilized by several authors and no reports have been published on the usage of the method on samples from the Barrandian area. To test the applicability of the method, samples from the Barrandian area were processed. The samples came from eleven localities representing six stratigraphic units (Paseky Shale, Jince Formation, Letná Formation, Kosov Formation, Daleje Shale and Roblín Member). All the units have been studied before by 'standard' methods of palynological processing. Various previously unreported fossils are described, including wiwaxiid sclerites, putative chaetognath remains and acritarch clusters. Furthermore, it is discovered, that the 'low-manipulation HF extraction' can also be used for extraction of originally calcareous fossils. The pilot study provides a further proof that the 'low-manipulation HF extraction' is a useful tool with the potential to significantly expand our knowledge of fossil assemblages. Key words: Small carbonaceous fossils, Cambrian, Ordovician, Devonian, Barrandian area
6

Eocrinoidní ostnokožci ze středního kambria barrandienské oblasti / Eocrinoid echinoderms from mid-Cambrian of the Barrandian area

Nohejlová, Martina January 2017 (has links)
This thesis deals with the topic of eocrinoid echinoderms from the Barrandian area (Příbram- Jince Basin, mid-Cambrian, Drumian). The thesis is presented as a compilation of five published papers and an introduction. The introduction is an overview of current knowledge about eocrinoid echinoderms. It also includes links to new information from the five included papers, and serves as a unifying element for these professional publications. The topic of the thesis is focused on a revision of selected specimens of eocrinoid echinoderms, and the study of their ontogeny, phylogeny, palaeoecology and systematic position. This thesis has also improved our understanding of early evolution of basal blastozoans. This is the first study of Cambrian ontogenetic development on eocrinoid material from the Czech Republic. Complete ontogeny was described on the genus Akadocrinus, and it was possible to establish two basic phases in the development of this genus: pre-epispire-bearing phase and epispire-bearing phase. The new primitive blastozoan Felbabkacystis is described from the Jince Formation - its unique body plan highlights evolution of the body wall among blastozoans. Palaeoecology and phylogeny of the genus Vyscystis was studied, and phylogenetic analysis suggests a basal position of lepidocystoids among...
7

Laurentia’s Oldest Brachiopods: Lower Cambrian Brachiopods of the Montezuma Range, Nevada / Laurentias äldsta brachiopoder: Lägre Kambrium brachiopoder från Montezumabergskedjan, Nevada

Saxén, Sara January 2017 (has links)
New brachiopod materials from the lower Cambrian (Global Stage 3 and lower Stage 4) of Esmeralda County, Nevada are described and their age distribution and diversity is discussed. The specimens originate from the Fritzaspis, “Fallotaspis”, “Nevadella” and Bonnia-Olenellus biozone which in the area correspond to the Campito Formation and the overlying Poleta Formation. As the specimens from the Gold Coin Member (Begadean Series) and the Montenegro Member (Waucoban Series) of the Campito Formation encompass the oldest samples, they were therefore prioritised as there was not enough time to describe all the specimens. The oldest known trilobites from Laurentia have previously been reported from the Gold Coin Member and it is of interest to determine if the brachiopods from the same member also are the oldest known from Laurentia.As many specimens are poorly preserved, especially the ones from coarse siliciclastic intervals, the determination of their systematic position is somewhat aggravated. Despite this, a diverse fauna including Lingulida, Obolellida, Naukatida, Kutorginida, Orthida and stem-group brachiopods have been successfully identified. A total of 16 taxa were noted for the Campito fauna, including the problematic and rare genera Swantonia and Spinulothele but unfortunately little new information could be gained regarding the characters for these rare genera. Four genera are reported for the first time from the area, not including material described under open nomenclature. / Under den geologiska tidsåldern Kambrium (542-488 miljoner år sedan) uppträder de första fossilerna av djurgruppen brachiopoder, eller armfotingar som de också kallas, tillsammans med många andra djurgrupper. Få platser i Laurentia (paleo-kontinent bestående av nutidens Nordamerika och Grönland) finns kvar som har bevarat de tidigaste förekommande brachiopod fossilerna. Esmeralda län i Nevada är en sådan plats och det här har det även spekulerats att Laurentias absolut äldsta brachiopod fossil skulle kunna hittas där. Denna avhandling fokuserar på att studera dessa brachiopod fossil från Nevada. När åldern för de äldsta studerade brachiopoderna (Begadean I ålder) i denna avhandling jämfördes med tidigare dokumenterade åldrar för äldre lägre Kambrium brachiopod fossiler stod det klart att dessa är de äldsta brachiopod fossilerna som hittats hittills.Många nya fossil prover har samlats in av J.S. Hollingsworth under en längre tid från Nevada och beskrivs häri. De nya fossilen innefattar både sällsynta släkten, så som Swantonia samt Spinulothele, och släkten som inte har hittats i Esmeralda län tidigare. Tyvärr erhölls lite ny information beträffande de sällsynta släktenas morfologiska egenskaper. Upptäkterna om de nya släkterna i området skulle kunna hjälpa oss att bättre kunna rekonstruera brachiopod faunan från Nevada samt att förstå spridningen av olika brachiopod grupper i framtiden.
8

Revize ontogeneze trilobita Sao hirsuta Barrande, 1846 z kambria ČR / Ontogeny of Sao hirsuta (Barrande, 1846) in the Cambrian of Czech Republic: revision

Laibl, Lukáš January 2012 (has links)
The Solenopleurid trilobite Sao hirsuta Barrande, 1846 is known from "Middle" Cambrian sedimentary rocks of the Czech Republic, Germany and Spain. It is one of the first trilobites on which ontogenetic development was described in detail (Barrande, 1852). This diploma thesis is the first modern revision of the ontogeny of this species for more than fifty years. Thesis is primarily based on quantitative methods and a detailed study of morphology of the exoskeleton. Changes in the dorsal exoskeleton during ontogenetic development of S. hirsuta, including the discovery of intrainstar morphological and size variability and the transition from isometric growth to the alometric growth, were described in detail by using quantitative methods (biometric measurements and geometric morphometrics). In the protaspid period different instars of S. hirsuta were recognized. Detailed morphological studies revealed several different morphotypes of protaspid stages. Some of which may represent different taxa. The morphology and the condition of the hypostome was described, including changes of hypostome during ontogeny. The study of segmentation in the species S. hirsuta shows hypoprotomeric development with the initial accumulation phase, middle equilibrium phase and terminal depletion phases. Key words: Sao...
9

Polymerized Tubular Silicates in Lower Cambrian Carbonates – Biology or Chemistry?

Green, Scott January 2022 (has links)
Shallow marine environments from the Lower Cambrian period were very different to shallow marine environments of today. Tubes of what was thought to be silica recovered from a partly dolomitized carbonate sample collected form a site near Indian Springs, Nevada could help further understand the chemistry and characteristics of such environments. The aim of this study is to present a detailed morphological description of the tubular structures found in the rock sample as well as to give a description of the environment in which they were produced. This was achieved by first studying the samples with several different analytical techniques including Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS) and subsequent evaluation of the obtained data. This resulted in the discovery that the tubular structures have a wall mainly consisting of non-detrital silica crystals. The crystals are arranged in string-like structures which overlap to form tube walls of varying thicknesses. The observed tubular structures are typically straight and ca. 0,23 to 0,25 mm long, but slightly curved and rare bifurcating tubes were also seen. The elemental mapping of a thin section of tubes showed that the wall-forming crystals consist mainly of silica (SiO2), however, small concentrations of calcium (Ca) were found inside many of the silica crystals leading to the conclusion that positive calcium ions may have acted as a seed for the silica crystals. A comparison of the tubular structures with other tubular fossils of the same geological time period is presented as well as a discussion of whether the specimens are of biological origin, and consequently a biosignature, as these could be used in future research when studying material from other planetary bodies. / Grunda marinmiljöer i nedre Kambrium var väldigt annorlunda från grunda marinmiljöer som finns idag. Små rör av vad som hypotiserades vara kiseloxid upptäckta i en dolomitiserad kalkstenstuff från Indian Springs, Nevada skulle kunna hjälpa att förstå kemin inblandad i bildandet av dessa samt bildningsmiljön i mer detalj. Syftet med detta projekt är att presentera en detaljerad morfologisk beskrivning av dessa rör samt försöka beskriv miljön i vilken de bildades. Undersökningen gjorde genom att först studera rören med olika mikroskoperingsmetoder inklusive ett optiskt mikroskop samt med ett svepelektronmikroskop (SEM), sedan analyserades proverna med Energidispersiv röntgenspektroskopi (EDS) för att detektera och kartera de grundämnena som fanns i rören. Resultaten av dessa metoder är att rören är cylindriska eller cigarrformade samt har en väggstruktur av kiseldioxidkristaller som sitter ihop som strängar av pärlor. Rören är huvudsakligen raka och har en längd på mellan 0,23 och 0,25mm, även böjda och förgrenade rör hat hittats, dock var mer sällsynta än de raka. Den kemiska analysen av ett tunnslip på några rör visade att de består till mestadels av kiseldioxid (SiO2) men koncentrationer av kalcium (Ca) hittades som indikerar att dessa kanske agerade som små frön för kiseldioxid att växa runt. En jämförelse av dessa rör med andra liknande fossilmed samma struktur och från samma tidsperiod är presenterad samt en diskussion kring rören som biosignatur och dess potentiella biologiskt ursprung samt användning i framtida forskning inom ämnet.
10

Linguliform Brachiopods from the terminal Cambrain to lower Ordovician Tiñu section, Mexico

Bornsäter, Barbro January 2008 (has links)
Tiñuformationen i Oaxaca, Mexiko är den enda fossilförande enheten från undre paleozoikum mellan den Laurentiska plattformen i nordvästra Mexiko och de Gondwanska lagerföljderna i Sydamerika. Det har nyligen visats att Tiñusektionen är en koncentrerad passiv kantlagerföljd med Gondwanakaraktär. Formationen delas upp i två delar; Yudachica från översta kambrium, som vilar okonformt på mellanproterozoisk grund, och Río Salinas från undre ordovicium (tremadoc). Formationen har tidigare studerats med avseende på dess avsättningsmiljöer och det fossila innehållet av trilobiter och konodonter vilka båda ger utmärkt biostratigrafisk kontroll över formationen. Ungefär 1000 exemplar av Linguliforma brachiopoder från tolv kalkstenslager från Tiñuformationen har studerats. Detaljerade undersökningar om taxonomi och stratigrafisk distribution av taxa har utförts. Faunan omfattar nio acrotretida taxa och en ny siphonotretid art och ett fåtal lingulida fragment. De acrotretida och det siphonotretida taxa har beskrivits grundligt och klassificerats till släkte. / The Tiñu Formation of Oaxaca State (Mexico) is the only fossiliferous lower Palaeozoic unit between the Laurentian platform in northwest Mexico and the Gondwanan successions in Andean South America. It has recently been shown that the Tiñu section is a condensed passive margin succession with Gondwanan character. The formation is divided into two members, namely, the uppermost Cambrian Yudachica Member, which rests nonconformably on a middle Proterozoic basement, and the Lower Ordovician (Tremadoc) Río Salinas Member. The formation has been studied with respect to its depositional environments and its fossil content of trilobites and conodonts, both providing excellent biostratigraphical control for the formation. About 1000 specimens of Linguliform brachiopods of twelve limestone horizons of the Tiñu Formation have been studied. Detailed investigations on taxonomy and stratigraphic distribution of the taxa have been made. The fauna comprises nine acrotretid taxa, a new siphonotretid species and a few linguloid fragments. The acrotretid and siphonotretid taxa have been thoroughly describes and classified to genus.

Page generated in 0.0903 seconds