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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

Skeletal ontogeny of Monodelphis domestica (Mammalia: Didelphidae) : quantifying variation, variability, and technique bias in ossification sequence reconstruction

Morris, Zachary Stephen 18 February 2014 (has links)
The field of evolutionary developmental biology (evo-devo) focuses on understanding the evolution of ontogeny and mechanisms of evolutionary change. Recently, taxonomic comparisons of the sequence of skeletal ossification have become prominent in evo-devo. However, most of these studies fail to consider two major issues: how the technique used to assay ossification and ontogenetic variation and variability may affect comparisons among taxa. This study focuses on the onset of ossification in the skeleton of Monodelphis domestica and quantifies the affects of variation, variability, and technique bias on reconstructions of ontogeny. Previous comparisons among mammalian taxa have used both computed tomography (CT) and clearing-and-staining (CS) to assess the presence or absence of skeletal elements (i.e., skeletal maturity). In this study, CT and CS were used on the same specimen to compare how these methods assess skeletal maturity. The comparisons of the same individual under reveal significant differences in how skeletal maturity is assessed by CT and CS techniques. Further, significant biases were recovered between techniques. CT is more likely to reveal cranial elements that CS does not, whereas CS is more likely to reveal appendicular elements that CT does not. To assess levels of variation and variability, Ontogenetic Sequence Analysis (OSA) was used to characterize the ontogeny of Monodelphis domestica. This revealed significant levels of variation with over 800 different ontogenetic pathways recovered for the onset of ossification of all skeletal elements studied. Additionally, high levels of variability were also reconstructed because the majority of specimens were found to exhibit non-modal ontogenetic sequences. This variability is more highly concentrated in the sequence of cranial ossification, suggesting potential modularity in ontogenetic variation and variability. Finally, OSA revealed that technique bias could importantly affect reconstructions of skeletal ossification sequences because no identical sequences were recovered by the CT and CS datasets. The results of this study demonstrate the importance of considering the primary nature of developmental studies, the specimen. Only by recognizing and quantifying the complexities of evo-devo research, especially natural variation and methodological biases, can more complete understandings of the evolution of ontogeny be had. / text
2

Landscape and Biotic Evolution of the Kochkor Basin, Kyrgyzstan

McLaughlin, Win 06 September 2018 (has links)
Kyrgyzstan is the single most seismically active country in the world. Accessing the past, and therefore future hazard of faults, necessitates a high-resolution understanding of the timing of different geologic events. With no radiometrically datable rocks from the Neogene of Kyrgyzstan, I herein present the first work formally describing Neogene vertebrate faunas from the Kochkor Basin of Kyrgyzstan. I utilize a combination of biostratigraphy and magnetostratigraphy to constrain the timing of when the vertebrate assemblages were emplaced, and have dated the three bone beds to all fall in the latest Miocene, spanning 9-5 million years ago. All four bone beds represent mass death assemblages, inferred to be from drought-caused mortality. The timing of the deposits corresponds to uplift in the Pamirs, Himalayan, and greater Tibetan Plateau, which would have blocked the Indian monsoon from reaching Central Asia, forever altering the climate and biota of the region. This change is reflected in the shifting mammals faunas, as evidenced by the novel rhinocerotid I describe in a phylogeographic context.
3

Phylogenetics of Panthera, Including Panthera Atrox, Based on Craniodental Characters

King, Leigha M., Wallace, Steven C. 01 January 2014 (has links)
The phylogenetic position of Panthera atrox within Felidae is still controversial despite many morphological and molecular studies addressing its relationships. This is in part due to the lack of consensus on a tree for Panthera. These inconsistencies suggest the need for further analysis and perhaps even different methodology to better understand pantherine evolution. Morphologic characters from the skull and dentary were analysed within Panthera to elucidate pantherine phylogeny. Extant taxa included Panthera leo (African lion), Panthera tigris (tiger), Panthera onca (jaguar), Panthera pardus (leopard), Uncia uncia (snow leopard) and Neofelis nebulosa (clouded leopard). Four outgroups were used: Crocuta crocuta (spotted hyena), Metailurus spp., Proailurus lemanensis and Pseudaelurus validus. Our study found a clade containing Panthera leo, Panthera tigris and Panthera atrox, suggesting that Panthera atrox is more closely related to the African lion and the tiger than the jaguar, in contrast to what has been recently proposed. Moreover, gross morphological similarities between Panthera atrox and Panthera onca are more likely the result of convergent hunting styles and/or prey selection, rather than phylogenetic affinity.
4

Primer registro fósil de Procyon cancrivorus (G. Cuvier, 1798) (Carnivora, Procyonidae) en la Argentina

Soibelzon, Leopoldo H., Zurita, Alfredo E., Morgan, Cecilia C., Rodríguez, Sergio, Gasparini, Germán M., Soibelzon, Esteban, Schubert, Blaine W., Miño-Boilini, Ángel R. 01 July 2010 (has links) (PDF)
We present the first fossil record of Procyon cancrivorus (Cuvier, 1798) for Argentina. Specimen PVE-F 44 (first lower molar) was exhumed from levels assignable to the Late Pleistocene (Lujanian) in the coastal cliffs of the Bermejo river in the vicinity of Villa Escolar, Formosa (26°36'S, 58°40 W). This is also the first South American record of Procyon with accurate stratigraphic provenance, since previous records from Brazil lack stratigraphic context. Procyonids are represented in South America by five living genera (Bassaricyon Allen, Nasuella Hollister, Potos Geoffroy Saint-Hilaire and Cuvier, Procyon Storr and Nasua Storr). Of these, only Procyon and Nasua have paleontological records (Late Pleistocene-Holocene) in Brazil, Uruguay and Bolivia. The results of geometric and traditional morphometric analyses comparing specimen PVE-F 44 with the two known Procyon species (P. cancrivorus and P. lotor) indicates the specimen belongs to the South American species P. cancrivorus. In addition, the associated palaeofauna is composed by intertropical (e.g., Holmesina paulacoutoi) and pampean-patagonian elements (e.g., Megatherium, Toxodon, Glyptodon, Pampatherium typum).
5

An assessment of phylogenetic origin in Chiroptera using the neuromodulatory system

Maseko, Busisiwe Constance 11 March 2008 (has links)
ABSTRACT The current study documents the findings from immunohistochemical examination of the brains of microbats and megabats (Chiroptera) using antibodies for cholineacetyltransferase (cholinergic neurons), tyrosine hydroxylase (dopaminergic, adrenergic and noradrenergic neurons), and serotonin (serotonergic neurons). The objective of the study was firstly to describe the anatomical organization and morphology of the neuromodulatory systems (nuclear complement) in both microbats and megabats, as there is no literature on these systems in the brains of chiropterans. Secondly, we aimed to investigate whether or not there are differences in these systems between the two suborders of chiroptera in hopes to shed some light on the phylogeny of the two, which is a controversial subject. The two groups were found to possess clear differences in their respective neuromodulatory nuclear complements. The differences observed between the two groups include a dorsal division of the locus coeruleus (A6d), which was absent in microbats but present in megabats, also the absence of an A4 in microbats but clear presence in megabats, and the parabigeminal (PBg) nucleus that was absent in microbats but clearly visible in megabats. The microbats were found to possess a complement that appeared similar to that of insectivores; whereas megabats had a complement resembling that of primates, carnivores and rodents. The differences found between the two groups suggest a diphyletic origin for the two groups.
6

Optimering av cellodlingsmedia genom kombinering av designade stamlösningar : med experimentell design och multivariat dataanalys

Ivermark, Katarina, Johansson, Caroline, Karlsson, Caroline, Lövgren, Jessica, Yuen, Pikkei, Ånäs, Sofia January 2013 (has links)
Syftet med projektet är att ta fram en metod för optimering av cellodlingsmedia som kan minska den tid och de resurser som dagens metoder kräver. Fem stamlösningar med adekvata komponenter designas och kombineras med olika flödeshastigheter till ett medium. Kombinationerna testas med experimentell design och analyseras med multivariat dataanalys för att få fram optimerade cellmedia. Odlingsmetoden som de fem stamlösningarna anpassas till är fed-batch, ett system där en av lösningarna är en baslösning och de resterande fyra designas till feedlösningar. De senare tillsätts i olika hastigheter till baslösningen anpassat efter cellernas näringsbehov. Strategin som har lagts upp för att designa stamlösningarna bygger på förhållandet mellan komponenternas förbrukningshastighet i de olika tillväxtfaserna. Under odlingen befinner sig cellerna i olika tillväxtfaser, i den exponentiella fasen ökar celldensiteten och i den stationära fasen sker större delen av produktionen av till exempel specifika antikroppar. Komponenterna i baslösningen förbrukas inte, eller i så liten mängd att de inte behöver tillsättas under odlingen, till skillnad från komponenterna i feedlösningarna som behöver tillsättas för att inte utarmas. I den exponentiella celltillväxtfasen, är behovet av de olika feedlösningarna flera gånger större än i den efterföljande stationära fasen. När önskad celldensitet är uppnådd så minskas flödeshastigheten från feedlösningarna och cellerna går in i stationärfas för att ge maximal produktion av önskad produkt. Projektet är uppbyggt av fyra delar: En litteraturstudie av nuvarande metoder för mediumutveckling, en beskrivning av framtagna stamlösningar, optimering av flödeshastigheten med experimentell design och multivariat dataanalys samt ett laborativt arbetsflöde av medias tillverkningsprocess.
7

Caracterização morfológica, citogenética e molecular de Mazama gouazoubira () a partir de um topótipo atual / Morphologic, citogenetics and molecular characterization of Mazama gouazoubira (Artiodactyla, Cervidae) from a current topotype

Borges, Carolina Heloisa de Souza [UNESP] 28 August 2017 (has links)
Submitted by Carolina Heloisa de Souza Borges null (carolhsborges@gmail.com) on 2017-09-28T18:45:34Z No. of bitstreams: 1 dissertacao_Carolina_Borges.pdf: 16277523 bytes, checksum: 32a1ce727f92fda87f7269eb6cc433c5 (MD5) / Approved for entry into archive by Monique Sasaki (sayumi_sasaki@hotmail.com) on 2017-09-29T17:33:47Z (GMT) No. of bitstreams: 1 borges_chs_me_jabo.pdf: 16277523 bytes, checksum: 32a1ce727f92fda87f7269eb6cc433c5 (MD5) / Made available in DSpace on 2017-09-29T17:33:47Z (GMT). No. of bitstreams: 1 borges_chs_me_jabo.pdf: 16277523 bytes, checksum: 32a1ce727f92fda87f7269eb6cc433c5 (MD5) Previous issue date: 2017-08-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O gênero Mazama é circundado de incertezas taxônomicas devido à sua alta diversidade cariotípica inter e intra-específica, origem polifilética e convergência morfológica. O veado-catingueiro é a espécie com a maior distribuição geográfica do gênero, ocorre no Brasil (com exceção da Amazônia), Paraguai, Uruguai, Bolívia e norte da Argentina, e, por causa desta abrangência, aliada ao fato de que apresenta alta variabilidade genética, morfológica e alta frequência de polimorfismos cromossômicos, ainda restam dúvidas sobre sua taxonomia com respeito ao número de subespécies existentes e o possível desdobramento destas em espécies. Por isso, o objetivo deste trabalho foi propor um neótipo para a espécie, através da caracterização de um espécime coletado na localidade tipo (topótipo), e assim auxiliar no esclarecimento da taxonomia de Mazama gouazoubira. O topótipo foi caracterizado por técnicas de morfologia tradicional (medidas cranianas e do pós-crânio, coloração da pelagem, biometria corporal), por análises citogenéticas (banda C, banda G, coloração Ag-RON, coloração convencional Giemsa) e moleculares (análises filogenéticas de genes mitocondriais). Pesquisas feitas em museus internacionais confirmam que o holótipo da espécie não existe, cumprindo requisito necessário para a proposta de neotipificação. O topótipo corroborou com os padrões morfológicos, citogenéticos e moleculares já descritos para o veado-catingueiro e por meio das análises comparativas com outros indivíduos da espécie e outros táxons do gênero, ficou claro que pertence à M. gouazoubira, permitindo a proposta de um neótipo para o táxon. / The genus Mazama is surrounded by taxonomic uncertainties due to its polyphyletic origin, high inter and intra-specific karyotype diversity and morphological convergence. The brown brocket deer is the species with the highest geographic distribution of the group due to its high ecological plasticity and because of this range, ally to the fact that presents high morfological and genetic divergence and high frequency of chromosomal polymorphisms, there are still doubts about the number of subspecies existing and the unfolding of these in species. Therefore, the objective of this work was to propose a neotype for M. gouazoubira through a characterization of a specimen collected in the type locality (topotype), and in this way, help to clarify the taxonomy of Mazama gouazoubira. The topotype was characterized by traditional morphological techniques (cranial measurements, skin color and body biometry), as well as by cytogenetic (C band, G band, Ag-NOR staining, conventional Giemsa staining) and molecular analyzes (phylogenetic analyzes of mitochondrial genes). After an extensive research in scientific collections, the results confirm the holotype does not exists, filling a necessary prerequisit for neotypification. The topotype corroborates the morphological, cytogenetic and molecular patterns already described in the literature for the brown brocket deer and through comparative analysys with other specimens and other taxons of the genus it is clear that the topotype belongs to M. gouazoubira, allowing the proposal of a neotype for the taxon.
8

A Contribution to the Evolutionary History of Ethiopian Hipparionine Horses (Mammalia, Equidae): Morphometric Evidence From de Postcranial Skeleton

Bernor, Raymond L., Scott, Robert S., Haile-Selassie, Yohannes 01 March 2005 (has links) (PDF)
A morphometric analysis of third metapodials and first phalanges of Middle Awash and Hadar hipparions dating from the 6.0-3.0 Ma interval was conducted using two methods. Morphological comparisons using standard metrics were made using: 1) log10 ratio diagrams; 2) size independent variables developed with reference to scaling trends for hipparions in general. Results of these analyses suggest that hipparion diversity during this temporal interval was relatively low. A single dominant gracile lineage of Eurygnathohippus Van Hoepen, 1930, most plausibly derived from the Lothagam (Kenya) species Eurygnathohippus feibeli (Bernor & Harris, 2003), would appear to have persisted throughout this interval and is marked by increases in size with measured change in metapodial and phalangeal morphology. A rarer, more robust form is found in the Ethiopian sample at 4.0 Ma and is morphometrically similar to Eurygnathohippus turkanense Hooijer & Maglio, 1973 from late Miocene horizons of Lothagam. Another smaller form, of uncertain systematic status, appears likely late in the Kada Hadar sequence, c. 3.0 Ma.
9

A Contribution to the Evolutionary Biology of Conohyus olujici N. SP. (Mammalia, Suidae, Tetraconodontinae) From the Early Miocene of LučAne, Croatia

Bernor, Raymond L., Bi, Shundong, Radovčić, Jakov 01 September 2004 (has links)
We describe here the topotypic series of Conohyus olujici n. sp. from the Croatian locality of Lučane. This sample was originally collected by local lignite miners in the 1930's, who conveyed the sample to the parish's Franciscan monk Dr. Josip Olujić. The Luč ane Conohyus sample includes seven lower jaws and jaw fragments; no upper cheek teeth have yet been recovered. Our use of bivariate statistics, log10 ratio diagrams and a cladistic analysis all reveal that C. olujici n. sp. is the most primitive member of the Conohyus clade. The analyses reveal that: of the sample considered, only two species are referable to Parachleuastochoerus, P. sp. and P. crusafonti; Parachleuastochoerus is the sister-taxon to Conohyus; Conohyus is a clade, and C. olujici n. sp. is the sister-taxon of the C. steinheimensis-C. simorrensis and C. sindiensis clades. Conohyus olujici n. sp. would appear to have occurred at a time when the genus enjoyed a relatively continuous geographic range that extended from southern Europe to South Asia. Conohyus olujici n. sp. was evidently adapted to swamp forest habitats. Its paleodiet, as evidenced by its thick molar enamel and labiolingually expanded posterior premolars, likely included hard object frugivory.
10

A Dental Microwear Texture Analysis of the Early Pliocene African Ursid Agriotherium africanum (Mammalia, Carnivora, Ursidae)

Stynder, Deano D., DeSantis, Larisa R.G., Donohue, Shelly L., Schubert, Blaine W., Ungar, Peter S. 01 December 2019 (has links)
The craniodental morphology of the early Pliocene ursid Agriotherium africanum has been studied extensively to reveal aspects of its dietary ecology. Results suggest that this large-bodied, long-legged, short-faced African native primarily consumed vertebrate matter. While many carnivoran families exhibit a clear functional relationship between craniodental form and performance on the one hand, and dietary behavior on the other, this is not always the case with Ursidae. Because of uncertainties regarding the appropriateness of using craniodental form to investigate ursid diets, questions still linger about the dietary ecology of Ag. africanum. Here, we report on a dental microwear texture analysis of six Ag. africanum lower second molars from the South African fossil site of Langebaanweg. Results support morphological evidence that suggests a diet focused on vertebrate soft tissue and bone. Unfortunately, results cannot clarify questions about mode of acquisition.

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