Thesis (Ph. D.)--University of Texas at Dallas, 2006. / Includes vita. Includes bibliographical references (leaves 118-128).

Thesis (M.S.)--Ohio University, August, 2004. / Includes bibliographical references (leaves 187-219).

Thesis (M.S.)--University of Nevada, Reno, 2008. / "August, 2008." Includes bibliographical references (leaves 142-149). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2008]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.

Thesis (M.S.)--Ohio University, August, 2004. / Title from PDF t.p. Includes bibliographical references (leaves 187-219)

The three approaches followed herein aim to improve our understanding of the paleobiodiversity andevolution of Silurian radiolarians. The first approach provides an exhaustive taxonomic description ofan entirely new radiolarian fauna recovered from two sections of the Cape Phillips Formation in theCanadian Arctic which accumulated in two different paleoenvironmental settings. The samples are datedby graptolites of the Gorstian Lobograptus progenitor Zone. The obtained radiolarian fauna includes 28species, of which 3 are new, and exhibits some of the best preserved Silurian radiolarians known so far.The stratigraphic range of several species was also extended. Then, in a second approach, a CT-Scan3D reconstruction of a specimen of Gyrosphaera cavea was conducted in order to resolve significantinternal structure taxonomic issues. Higher level radiolarian classification is based on internal structures,and classical methods of observing these features repeatedly failed to uncover them. The 3D imagingrevealed a «double» coiling of the specimen that has proved useful in understanding how it grew.Eventually, the third approach is a completion of published taxonomic works in the Silurian with theaim of providing diversity trends through analyses of these radiolarian occurrences. A biotic crisis canbe observed in the Homerian, exhibiting both high extinction and low origination rates, and may belinked with enhanced marine productivity. / De tre projekten som utvecklas här har som mål att fokusera på trender inom evolutionen ochmångfalden av en grupp planktoniska mikroorganismer från Silur (från -443 till -419 Ma). I ett förstaprojekt beskrivs en helt ny fauna radiolarier som hittats i två lokaliteter på de kanadensiska arktiskaöarna, och som har deponerats i olika miljöförhållanden under Silur. Detta material daterades med hjälpav graptoliter, en grupp utdöda svalgsträngsdjur som är mycket användbara för paleozoiska dateringar,till en ålder överensstämmande med Gorstian (-427 till -425 Ma). Denna kanadensisk-arktiska fauna avradiolarier består av 28 arter (varav 3 är nya) och uppvisar några av de bäst bevarade fossilerna frånSilur överhuvudtaget. Den stratigrafiska bredden, vilket är livstiden, av flera arter har också förlängts.Därefter, i ett andra projekt, skapades en 3D-rekonstruktion av ett exemplar av Gyrosphaera cavea medhjälp av mikrotomografi för att observera och beskriva komplexa interna strukturer. Faktum är attklassificeringen av Radiolaria består till stor del av analysen och beskrivningen av dessa internastrukturer och många klassiska metoder som har använts för att observera dem, såsom med hjälp avsvepelektronmikroskop, har misslyckats konsekvent. 3D-avbildningen visade en komplex dubbelrullandeav strukturen i exemplaret, som har visat sig vara användbart i sökandet för att förstå dennesutveckling. Det tredje projektet är slutförandet av en samling av samtliga publicerade arbeten röranderadiolarier från Silur med syfte att klargöra trender inom diversitet för hela perioden genom analyser avförekomsten av dessa radiolarier. Ett utdöende kan observeras under Homerian (-430 till -427 Ma), somtroligen orsakades av frekventa utdöenden och en låg artbildningshastighet.

Graduation date: 1997

The presented thesis is focused on the Radiolaria of the Czech Cretaceous Basin. The studied material was collected in Březno u Loun and in the Úpohlavy quarry. Biology, ecology and morphology, as well as systematics of the whole group is discussed. An important part of this thesis constitutes of the geological settings of Cretaceous, Czech Cretaceous Basin and both localities. 26 samples from Březno and 24 samples from the Úpohlavy quarry have been studied using several methods with the aim to obtain most numerous and best preserved communities possible. Despite poor preservation of the shells, 9 species have been identified. Several shells have been assigned at least to the genus or order levels. Species of Dictyomitra communis (Squinabol, 1904), Dictyomitra cf. napaensis Pessagno, 1976, Turbocapsula cf. giennensis O'Dogherty, 1994, Novixitus cf. mclaughlini Pessagno, 1977, Stichomitra cf. stocki (Campbell & Clark, 1944), Stichomitra communis Squinabol, 1903, Stichomitra japonica (Nakaseko & Nishimura), in Nakaseko et. al., 1979, Holocryptocanium barbui Dumitrica, 1970, cf. Pseudoaulophacus pargueraensis Pessagno, 1963 and genera of Orbiculiforma, Stichomitra, cf. Cryptamphorella have been reported in the Czech Cretaceous Basin for the first time.

Graduation date: 1991

Thesis (Ph. D.)--Columbia University, 1975. / Includes bibliographical references (leaves 243-251).

Extensive fossil collections from the upper part of the Sandilands and the lowermost Ghost Creek Formations allowed a detailed taxonomic study of the latest Hettangian to earliest Phensbachian ammonoid fauna of the Queen Charlotte Islands. 61 taxa, allocated to 27 genera, are described. Sunrisites senihlevis, Plesechioceras yakounense, Tetraspidoceras pacificum and Tetraspidoceras recognitum are introduced as new species. The vertical distribution of ammonites, documented in measured sections, serves as a basis to distinguish six successive assemblage zones: the Canadensis Zone, "Coromceras" Zone, Arnouldi Zone, Varians Zone, Harbledownense Zone, and Recognitum Zone. Of these only the Canadensis Zone was established earlier, the remaining five are defined here for the first time. This zonation permits high-resolution correlation of the sections. The total thickness of uppermost Hettangian to lowermost Pliensbachian strata in sections on Kunga Island is estimated at 385 m. A comparison of selected zones in different sections shows a subtle thickness increase to the south. The contact of the Sandilands Formation and the overlying Ghost Creek Formation is diachronous, younging gradually to the south. The faunal succession in the Queen Charlotte Islands agrees well with that of the Taseko Lakes area and Nevada, promising regional applicability of the proposed zones. Intercontinental correlation with the northwest European standard zonation is possible at diffrent levels. The Hettangian/Sinemurian boundary is contained within the Canadensis Zone. It is best approximated by the first appearance of Badouxia columbiae and Metophioceras spp. The position of the Recognitum Zone at the Sinemurian/Pliensbachian boundary remains problematic; most evidence on hand points to its Pliensbachian affinities. The ammonite fauna consists of taxa with pandemic, Tethyan, Athabascan, East Pacific, and Pacific distribution. Provincialism was not prominent but existed during the Sinemurian time. The high proportion of Tethyan forms is in accord with the theory suggesting a more southerly original paleolatitude for Wrangellia. The distribution of Tethyan forms can be explained by the early opening of the Hispanic Corridor, proven to be in existence by the Pliensbachian. Alternatively, the pantropic distribution model cannot be ruled out, although the faunal record from the eastern Tethys is inadequate to prove it. Thestrong representation of Athabascan and East Pacific elements renders long-distance longitudinal tectonic dislocation of Wrangellia unlikely. The paleoecology and taphonomy of ammonites, associated macrofauna, and trace fossils is used for paleoenvironmental reconstruction. The general lack of bioturbation, predominance of thin-shelled, presumably pseudo-planktonic bivalves, and the intact preservation of fish and a crinoid specimen indicate prevailing oxygen deficient bottom conditions. Trace fossils provide evidence for periodic improvements of bottom oxygenation. Different modes of ammonite preservation are controlled by shell morphology as well as the varying sedimentation rate and diagenetic regime. The latter reflects changes in redox conditions in the upper sediment layers. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate