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  • 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

The evolution of the cuticle in early angiosperm leaves from the Lower Creatceous Potomac Group (Atlantic coastal plain, U.S.A.)

Upchurch, Roland Garland. January 1981 (has links)
Thesis (Ph. D.)--University of Michigan, 1981. / A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Botany) at the University of Michigan 1981.
2

A total evidence analysis of the evolutionary history of the Thunnosaur ichthyosaurs

Lawrence, Jessica Danielle. January 2008 (has links)
Thesis (M.S.)--Bowling Green State University, 2008. / Document formatted into pages; contains ix, 72 p. : ill. Includes bibliographical references.
3

Late Maastrichtian paleoclimatology and the paleobiology of Raceguembelina fructicosa, Contusotruncana contusa and Rugoglobigerina rugosa inferred from single specimen [delta]¹³C and [delta]¹⁸O data /

Isaza Londoño, Carolina. January 2004 (has links)
Thesis (M.S.)--University of Missouri-Columbia, 2004. / Prepaging (vii) included in total paging. Typescript. Includes bibliographical references. Also available on the Internet.
4

Paleoecology of the Tiawah limestone middle Pennsylvanian of northeastern Oklahoma

Parker, Calvin Alfred, January 1958 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1958. / Typescript. Abstracted in Dissertation abstracts, v. 18 (1958) no. 3, p. 1013-1014. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 126-128).
5

Late Maastrichtian paleoclimatology and the paleobiology of Raceguembelina fructicosa, Contusotruncana contusa and Rugoglobigerina rugosa inferred from single specimen [delta]¹³C and [delta]¹⁸O data

Isaza Londoño, Carolina. January 2004 (has links)
Thesis (M.S.)--University of Missouri-Columbia, 2004. / Prepaging (vii) included in total paging. Typescript. Includes bibliographical references. Also available on the Internet.
6

Studies on living and fossil Charophyte oosporangia

Leitch, A. January 1986 (has links)
No description available.
7

Contributions to Exceptional Fossil Preservation

Muscente, Anthony Drew 21 April 2016 (has links)
Exceptionally preserved fossils—or fossils preserved with remains of originally non-biomineralized (i.e. soft) tissues—constitute a key resource for investigating the history of the biosphere. In comparison to fossils of biomineralized skeletal elements, which represent the majority of the fossil record but only a fraction of the total diversity that existed in the past, exceptionally preserved fossils are comparatively rare because soft tissues are rapidly destroyed in typical depositional environments. Assemblages of such fossils, nonetheless, have received special attention among scientists in multiple fields of Earth and life sciences because they represent relatively 'complete' windows to past life. Through such windows, researchers are able to reconstruct original biological features (e.g. soft tissue anatomies) of extinct organisms and to describe the structures and compositions of ancient soft-bodied paleocommunities. To accomplish these goals, however, researchers must incorporate background information regarding the pre- and post-burial histories of exceptionally preserved fossils. In this context, my dissertation focuses on the environmental settings, diagenetic conditions, geomicrobiological activities, and weathering processes, which influence the conservation of original biological features within exceptionally preserved fossils and control their occurrences in time and space. An improved understanding of these critical factors involved in exceptional fossil preservation will ultimately our advance our knowledge regarding the history of the biosphere and the Earth system as a whole. Each chapter of original research in this dissertation includes an innovative and distinct approach for studying exceptional fossil preservation. The second chapter describes environmental and geologic overprints in the exceptional fossil record, as revealed by a comprehensive statistical meta-analysis of a global dataset of exceptionally preserved fossil assemblages. Moving from global to specimen-based perspectives, the second and third chapters focus on minerals (products of geomicrobioloigcal, diagenetic, and weathering processes) and carbonaceous materials replicating exceptionally preserved fossils. The third chapter examines the causes of preservational variations observed among organophosphatic tubular shelly Sphenothallus fossils in the lower Cambrian of South China using an experimental approach. (Although Sphenothallus is not an exceptionally preserved fossil sensu stricto, its conservation of original organic matrix tissues in South China provides key insights into the preservation of carbonaceous material within fossils.) Lastly, the fourth chapter presents data acquired using various in situ nanoscale analytical techniques to test the hypothesis that microstructures within exceptionally preserved microfossils of the Ediacaran Doushantuo Formation of South China are some of the oldest putative cylindrical siliceous demosponge spicules in the fossil record. Collectively, these chapters describe environmental, authigenic, diagenetic, and weathering processes that affect exceptional fossil preservation, and highlight innovative methods and approaches for testing major paleobiologic and geobiologic hypotheses regarding exceptionally preserved fossils. / Ph. D.
8

Musteline (Mustelidae) fossil remains from the Early Pliocene Gray Fossil Site of Tennessee: the first pre-Pleistocene record of weasels in the Eastern United States

Peery, Ronald W., Samuels, Joshua X. 12 April 2019 (has links)
The Mustelinae (weasels, stoats, minks, and ferrets) are a subfamily of small, elongate-bodied mustelid carnivorans (Carnivora: Mustelidae) that originated during the Late Miocene. Mustelines are the most abundant group of carnivorans in the world today and are commonly found at Pleistocene-aged sites across their range; however, their lack of a more complete fossil record has left many questions regarding the evolution of early mustelines unanswered. Here we report a new occurrence of a musteline from the Early Pliocene age (4.9 – 4.5 Ma) Gray Fossil Site in northeastern Tennessee. Morphology of the P4 and M1 are consistent with the dental characteristics of Mustelinae, and thus this find represents the first reported pre-Pleistocene occurrence of a musteline in the eastern United States. Morphology of the specimens is distinct from the well-known Miocene ischyrictine mustelid Plionictis, but falls within the range of variation observed within the extant genera Mustela and Neovison. Linear measurements also fall within the size ranges of those genera. Distinguishing Mustela from Neovison based on morphological characters alone is very difficult and recent phylogenetic studies differentiating the two have been based exclusively on genetic evidence. Further study will hopefully allow us to place a confident identification on the musteline from Gray. The small, hypercarnivore niche of mustelines is one that was previously not recognized among fauna at the Gray Fossil Site, and improves our understanding of the site’s paleoecology.
9

Paleoecology and Taphonomy of Ediacaran macrofossils from the Khatyspyt Formation, Olenek Uplift, Siberia

Bykova, Natalia 29 September 2017 (has links)
The Ediacaran Period (635 – 541 Ma) is a critical transition in the history of the Earth and life. It is marked by the appearance of enigmatic Ediacara-like fossils and macroalgae, which had existed since the early Proterozoic, but started to diversify morphologically and ecologically during this geological period. Nevertheless, paleontologists have been studying Ediacaran fossils for more than a century, the key questions about these fossils remain unanswered, including their phylogenetic affinities, taphonomic history, ecology, and paleoenvironmental distribution. Thus, new ways of investigation need to be employed to unveil enigmas of Ediacaran organisms. As well as, scientists need to engage other representatives of Ediacaran assemblages, such as macroalgae, to fully understand how those communities operated in the past. The chapters of this original research in this dissertation demonstrate innovative approaches and methods for studying the paleoecology and taphonomy of Ediacaran macrofossils. The second chapter presents the results of a geochemical analysis to resolve taphonomic and paleoecological questions about the Ediacara-like discoidal holdfast fossil Aspidella. Stable isotope data of organic carbon, carbonate carbon/oxygen, and pyrite sulfur were integrated with iron speciation data to reconstruct the taphonomy, paleoecology, and paleoenvironments of Aspidella fossils. The third chapter presents results from a comprehensive analysis of macroalgae from Proterozoic to early Paleozoic. In this study, a database of macroalgal fossil was updated and analyzed in order to gain insights into the big-picture evolutionary patterns of macroalgal morphology and ecology through time. These methods and approaches offer new opportunities to test major paleobiologic and geobiologic hypotheses, thus improving our understanding of the history of the biosphere and the Earth system. / Ph. D.
10

Classification and phylogeny of Cenozoic trissocyclidae (Radiolaria) in the Pacific and Caribbean basins /

Goll, Robert Miles January 1967 (has links)
No description available.

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