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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.
441

Remodeling the Fossil Record| Analysis of Emergent Evolutionary and Ecological Patterns

Smits, Peter David 10 August 2017 (has links)
<p> Macroevolution and macroecology are concerned with the patterns in evolutionary and ecological data, respectively, which arise when observing multiple species over time and/or space. Species extinction and species pool functional composition are the macroevolutionary and macroecological patterns at the heart of this dissertation. The hypotheses and analyses in the three studies forming this dissertaiton were all framed in terms of how species functional traits can shape these emergent patterns. </p><p> In my first study, I analyzed the Cenozoic fossil record of North American mammals to test two long standing hypotheses: the survival of the unspecialized hypothesis, and the Law of Constant Extinction. My analysis centers around a model of species duration as a function of multiple species traits, species&rsquo; phylogenetic relatedness, and species&rsquo; origination cohort. My results support the conclusion that generalist species will, on average, have a greater duration than more specialized species. I also find that species extinction risk increases with species duration, a result that is counter the Law of Constant Extinction. Additionally, I find that only some of the factors associated with extinction risk for Modern mammals could be considered risk factors for mammals from the rest of the Cenozoic, indicating a difference between the modern biodiversity crisis and &ldquo;normal&rdquo; extinction dynamics. </p><p> My second study also deals with the survival of the unspecialized and the Law of Constant Extinction, but focuses on a different system: post-Cambrian Paleozoic brachiopods. An additional aspect of this study is an analysis of the relationship between extinction intensity and the strength of trait selection. I find support for greater survival among environmental generalists than specialists. I also find evidence that for geographic range and environmental preference, as extinction intensity increases, the selective importance of these traits increases. This result is evidence for a qualitative difference between background and mass extinction. The final study is an analysis of the changing functional composition of the North American mammal regional species pool over the last 65 million years. The goals of this analysis are to understand when functional groups are enriched or depleted, and how changes to environmental context may shape these changes. I find that mammal diversity is more strongly shaped by changes to origination probability rather than changes to extinction probability. I also find that all arboreal ecotypes declined throughout the Paleogene and disappeared from the species pool by the Neogene. Additionally, I found that most herbivore ecotypes expand their relative contribution to functional diversity over time. </p><p> My desire with this dissertation is to present the types of analyses and results that are possible through a synthesis of macroevolution and macroecology. The first step to building any dialogue is to agree on a common language and I&rsquo;ve emphasised an expressive statistical framework with which to phrase our questions in a common tongue. My hope is that this studies serve as an example of how to use paleontological data to unite questions about the processes underlying macroevolutionary and macroecological patterns.</p><p>
442

Corals from the Rundle formation (Mississippian) of Banff, Alberta

Frebold, Fridtjof Albert January 1955 (has links)
This thesis contains descriptions and illustrations of six genera and seven species of fossil corals collected by the writer on Mount Norquay, Banff National Park, Alberta. A brief discussion of the fossil locality and stratigraphy of the Rundle formation in that area is given. As a result of statistical research and graphic representation, a new species Faberophyllum multiseptatum is described. The new species is closely related to F. languidum, F. leathamense, F. pisgahense, and F. araneosum. The species Ekvasophyllnm banffense is proposed, and the species Lophyphyllum ? cascadense Warren is redescribed and referred to the genus Ekvasophyllum. The genera Triplophyllites and Cyathoclisia, which previously have not been described from Canada, are recognized and briefly discussed. The descriptions of Lithostrotion whitneyi and Lithostrotionella banffensis are revised and adequately illustrated. From the study of corals from the upper Rundle formation the writer concludes that these may be important horizon markers, and recommendations are made for more extensive and detailed work on this subject. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
443

Comparative osteology of tapiromorph perissodactyls and its phylogenetic implications

Holbrook, Luke Thomas 01 January 1997 (has links)
Despite a rich fossil record and much attention from paleontologists, the phylogeny of mammalian order Perissodactyla (including extant horses, rhinoceroses, and tapirs) is poorly understood. There are at present no well-supported phylogenetic hypotheses of the interrelationships of perissodactyls, nor has the position of this order among other eutherian orders been established. The main hindrance to this understanding is a lack of thorough and rigorous analysis of characters and taxa. This study attempts to overcome this problem by analyzing characters from all aspects of the skeleton in a broad diversity of taxa for one major perissodactyl lineage, the Tapiromorpha. Studies of interordinal and intraordinal relationships of the Perissodactyla have previously been effectively incompatible, because these two types of studies utilized different types of characters. Interordinal studies focused on cranial and postcranial characters, whereas intraordinal studies relied heavily on tooth morphology. This study focuses on cranial and postcranial osteology. The cranial and postcranial skeleton of a broad range of tapiromorphs is described. These descriptions have two purposes: (1) to identify potentially useful characters for use in a phylogenetic analysis of tapiromorphs; and (2) to provide a reference on tapiromorph osteology that will facilitate the inference of primitive tapiromorph character states for higher-level analyses. Putative tapiromorphs include "tapiroids," rhinocerotoids, and chalicotherioids. Numerous representatives of these groups are compared with other perissodactyls (equoids and brontotheres) and eutherians thought to be closely related to perissodactyls. Cranial and postcranial characters drawn from the afore-mentioned descriptions are combined with selected dental characters in a phylogenetic analysis of tapiromorph genera. For the sake of clarity, higher-level taxonomic groups are defined a priori. The results of the phylogenetic analysis demonstrate that there is no unequivocal evidence for including chalicotherioids or the traditional primitive "tapiroid" Homogala in the Tapiromorpha (as defined here). The analysis supports the close relationship between tapirs and rhinoceroses relative to horses, as well as clades that fulfill the definitions of Tapiroidea and Rhinocerotoidea. The results of the phylogenetic analysis provide the basis for a revised classification of the Tapiromorpha.
444

The articulation of social inequality and faunal resource use in the Preclassic community of Colha, northern Belize

Shaw, Leslie Carol 01 January 1991 (has links)
This dissertation evaluated the interactional dynamics of emerging social inequality and the economics of basic necessities during the early development of Lowland Maya civilization. Basic necessities, including clothing, shelter, and utilitarian tools, were all affected in some way by the changes in access to and distribution of resources, technology, and information. This study focuses on one specific relationship: that between increasing social inequality and the procurement and distribution of animal resources. This research problem is addressed using faunal remains from the site of Colha in northern Belize. The faunal assemblage (totaling 14,553 bones/bone fragments) was recovered from Preclassic Period (1,000 B.C.-A.D. 250) residential deposits. The 1,250 years represented in the assemblage cover the time when the Maya shifted from small autonomous communities to hierarchically ranked centers, many of which specialized in the production and/or exchange of goods for regional consumption. The faunal data from Colha were evaluated against the changes in social complexity documented for this period. A distinct patterning in the use of faunal resources during the Preclassic was observed. The early settlers of Colha (roughly 1,000-600 B.C.) utilized low-bush terrestrial, wetland, and aquatic species nearly equally. The prominent use of wetland and aquatic resources suggests that wetland agriculture may have been used. The five hundred years that followed saw a gradual shift toward a heavier use of wetland and aquatic resources, probably due to wetter conditions and to the biodegradation caused by land clearing and heavy faunal exploitation. In the Late Preclassic there was a marked change in faunal use, beginning approximately 100 B.C. This includes a heavier reliance on terrestrial species, an increased use of dog for food, and a greater utilization of distant habitats, such as marine and high-forest environments. These changes required modifications in the social aspects of food procurement and distribution, including exchange relationships, and not simply an intensification of past strategies. It is proposed that households could use their elevated status (and accompanying accumulation of wealth and power) to shift from a strategy of direct food procurement to one in which food could be acquired indirectly through exchange and/or tribute.
445

Reburying a Mastodon: A Digitization Workflow for Vertebrate Paleontological Spatial Data

Bushell, Matthew, Widga, Chris 12 April 2019 (has links)
Geographic Information Systems (GIS) can be a powerful paleontological tool. This project’s goal was to digitally reconstruct a large, mostly-articulated mastodon (Mammut sp.) excavated from the Gray Fossil Site during the 2015 to 2018 field seasons. This was done by compiling total station survey data, field notes, sketch maps, and cataloged specimen data within ArcGIS Pro. Field drawn sketch maps were geo-referenced to relevant survey points. Then, a polygon layer was created by tracing the spatially referenced field drawings. Each polygon was given the specimen’s designated field number and connected to a table containing all associated field data. The result was a polygon layer that displayed all major bones and bone fragments of the mastodon which was linked to museum catalog information. Researchers can use this digital product to interpret site taphonomy, examine the distribution of skeletal elements or fossil taxa, or potentially identify areas of interest for future excavations. This workflow will streamline future specimen digitization efforts at the Gray Fossil Site.
446

Fossil, data, and information driven paleontology

Yu, Congyu January 2022 (has links)
Paleontology is based on fossils but what is the link between fossil specimens and our reconstruction of life history seems to be ambiguous. The majority of paleontological studies focus on fossil morphology to infer their phylogenetic status, but recently increasing number of studies emphasize the role of paleontological data rather than particular specimens. Datasets construction and data processing are still basic in many paleontological studies, thus hampering the transition towards data-driven paleontology. More importantly, there has been a lack of understanding of the difference between data and information embedded inside. In this thesis, I present examples of three kinds of paleontological studies driven by fossil, data, and information, respectively, which shows the reconstruction of evolutionary history via different level of features from fossils. Chapter 1 shows the evolution and development of ceratopsian dinosaurs with emphasis on the fossil materials from the Gobi Desert, Mongolia. Chpater 1.1 reports Beg tse, a neoceratopsian dinosaur that is sister to all other know neoceratopsians, and morphologically and temporally between neoceratopsians and more basal ceratopsians. In chapter 1.2, to further explore the development of Protoceratops as well as other ornithischian dinosaurs, two embryonic Protoceratops skulls are CT-scanned and compared with more mature Protoceratops and other ornithischian dinosaurs. The results show strong peramorphosis in ceratopsian dinosaurs and conservative cranial development in stem ornithischians. Chapter 1.3 reports a new species of Protoceratops, P. tengri, which bears a regular wavy pattern along its neck frill that is absent in almost all previously reported Protoceratops. Such structure may function as display as it seems to be the ancestral form of other patterned cranial structures in more derived ceratopsids. Chapter 2 focus on data-driven paleontological studies, especially the applications of artificial intelligence (AI). Chapter 2.1 is based on the data comprised from chapter 1.2, deep neural networks (DNNs) are used to segment CT slices of embryonic Protoceratops fossils and have reached human comparable performance, but the generalization ability of such models remains questionable. Chapter 2.2 shows DNNs-based localization and segmentation of osteons in histological thin sections from Alvarezsaurian dinosaurs. The results indicate a truncated development pathway rather than compressed development during the miniaturization of this group. Chapter 2.3 is a short review about previous AI applications in paleontology, in which a large portion is based on data from foraminifera, insects, and other microfossils while only few are working with vertebrate fossils. There are approximate 10-year gap in algorithms and datasets between paleontology and mainstream AI studies. Chapter 3 explores the even basic level of data-driven paleontology, the information. Under the framework of information theory and communication system engineering, chapter 3.1 introduces the basic concepts of information theory and how they are represented in paleontological studies. Chapter 3.2 quantify the information entropy, mutual information, and channel capacity in morphological character matrices of various groups of vertebrates. The results suggest alternative weighting strategy in phylogenetic analysis and question current construction strategy of morphological character matrices. Chapter 3.3 makes further perspective about the application of information theory in paleontological study by treating it as a communication system. During the last two decades, the increase of data and appearance of novel methods have led many research fields transiting towards data driven. However, the construction of datasets, harnessing of novel data processing methods, and establishment of a general theory all indicate significant lags between paleontology and many other research fields. This thesis provides the very initial examples towards data-driven paleontological studies.
447

Mice and Rats (Rodentia: Cricetidae) from the Pliocene Age Gray Fossil Site of Tennessee and Their Paleoecological Implications

Xu, Ziqi, Sam, Joshua, Dr. 07 April 2022 (has links)
Cricetidae, which includes a wide range of mice, rats, and voles, is the second-most diverse and abundant family of mammals. Distributed across the Americas and Eurasia, this rodent family has been extensively studied for its success and adaptability in the face of climate and habitat change, and its utility for ecological reconstruction and the biochronology. While cricetids are known from many fossil sites in western North America, few have been found and studied from the terrestrial sites in the east prior to the Pleistocene. The Gray Fossil Site (GFS) in eastern Tennessee is well-known for its diverse flora and fauna, particularly large mammals. Small mammals from the site have remained understudied, and although a few studies have mentioned cricetids, a comprehensive investigation is needed to describe the large number of cricetid specimens found at GFS. This project uses qualitative and quantitative methods to examine the morphology of fossil cricetids from GFS, focused on molars and jaw elements because of their abundance and the rich taxonomic and ecological information they provide. Materials have been studied using a stereomicroscope and photographed using a digital microscope camera. Occlusal morphology is described and compared to modern cricetids and published records from across North America. Specimens from GFS include at least 5 taxa, and the two most abundant taxa at the site are the woodrat Neotoma, which has high-crowned molars and still lives in the region today, and the deer mouse-like Postcopemys, which has low-crowned molars. While many GFS specimens can be categorized into these two genera, distinctive morphological variations seen in some individuals suggest the presence of new species. The array of cricetids present is distinct from those at contemporaneous sites and reinforces the spatial and temporal uniqueness of the Gray Fossil Site. Situated in the biodiversity hotspot in the Appalachian region today, GFS provided habitats for cricetid taxa with diverse body sizes and dietary preferences in the Pliocene.
448

Stratigraphy and palaeoenvironment of the Carboniferous Jurassic Karoo Supergroup in the Lebombo-Tshipise basin

Clayton, Katherine E January 2017 (has links)
A dissertation presented to the Faculty of Science, University of the Witwatersrand, in partial fulfillment of the requirements for the degree of Master of Science. August, 2017 / The Karoo Supergroup represents a highly complete sedimentary succession that was deposited in several basins throughout southern Africa during the late Palaeozoic and Mesozoic (Carboniferous-Jurassic). While research in the Lebombo-Tshipise Basin of southern Africa has largely focused on lithological description of Karoo sediments or structural features of the basin, little effort has been made to describe the palaeoenvironments recorded in the sediments, or the basin fill’s response to major tectonic or climatic events. To address palaeoenvironmental reconstruction, lithostratigraphic analysis resulted in defining 11 facies associations from the Tshidize, Madzaringwe, Mikembeni, Fripp, Solitude, Elliot and Clarens Formations in the Pafuri sub-basin of the Lebombo-Tshipise Basin. Twenty boreholes drilled in Kruger National Park by the Council for Geoscience in 1979 record largely stable and consistent deposition of the Tshidize, Madzaringwe and Mikembeni Formations during the Permian. The Mikembeni Formation thins dramatically southwards, whereas the overlying Triassic successions tend to wedge out to the east. Late Triassic and Jurassic sediments directly overlie Precambrian basement in the southernmost boreholes. Significant thickness differences between the western and eastern boreholes indicate a large fault, which likely represents a rift shoulder. The palaeoenvironments in this basin are similar to those of the Main Karoo Basin, but quantitative analyses suggest a more humid environment in the Late Triassic Elliot Formation. Sauropodomorph fossils validate assignment of formerly mapped Solitude Formation as actually being the Elliot Formation. Palaeosols in the Elliot are consistent with either Oxisols or Argillisols. Wet desert conditions, evidenced by burrows produced by invertebrate communities, and tectonic activity, suggested by seismites, persist into the Early Jurassic Clarens Formation. / MT2018
449

The osteology and relationships of aquatic eosuchians from the Upper Permian of Africa and Madagascar /

Currie, Philip J. January 1981 (has links)
No description available.
450

Diatoms as recorders of sea ice in the Bering and Chukchi Seas: Proxy development and application

Caissie, Beth E 01 January 2012 (has links)
The recent, rapid decline in Arctic summer sea ice extent has prompted questions as to the rates and magnitude of previous sea ice decline and the affect of this physical change on ice-related ecosystems. However, satellite data of sea ice only extends back to 1978, and mapped observations of sea ice prior to the 1970s are sparse at best. Inventories of boreal ecosystems are likewise hampered by a paucity of investigations spanning more than the past few decades. Paleoclimate records of sea ice and related primary productivity are thus integral to understanding how sea ice responds to a changing climate. Here I examine modern sedimentation, decadal-scale climate change in the recent past, and centennial- to millennial-scale changes of the past 400 ka using both qualitative and quantitative diatom data in concert with sedimentology and organic geochemistry. Diatom taxonomy and corresponding ecological affinities are compiled in this study and updated for the Bering Sea region and then used as recorders of past climate changes. In recent decades, the Pacific Decadal Oscillation and the strength of the Aleutian Low are reflected by subtle changes in sediment diatom assemblages at the Bering Sea shelf-slope break. Farther back in time, the super-interglacial, marine isotope stage (MIS) 11 (428 to 390 ka), began in Beringia with extreme productivity due to flooding of the Bering Land Bridge. A moisture-driven advance of Beringian glaciers occurred while eustatic sea level was high, and insolation and seasonality both decreased at the global peak of MIS 11. Atlantic/Pacific teleconnections during MIS 11 include a reversal in Bering Strait throughflow at 410 ka and a relationship between North Atlantic Deep Water Formation and Bering Sea productivity. Finally, concentrations of the biomarker-based sea ice proxy, IP25, are compared to sea ice concentration across the Bering and Chukchi seas. Changes in the concentration of IP25 in the sediments may be driven by the length of time that the epontic diatom bloom lasts. When combined with a sediment-based proxy for sea surface temperatures, IP 25 can be used to reconstruct spring ice concentration.

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