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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

Whiterockian (middle Ordovician) graptolites of the Lower Member of the Vinini Formation, Roberts Mountains, Eureka County, Nevada

Schuster, Erin B. 31 March 2015 (has links)
<p> The Ordovician strata of the Lower Member of the Vinini Formation comprise a sequence of greenstone, sandstone, shale, and siltstone representing the prograding and retrograding of submarine fans along the continental margin. Although graptolites are normally preserved within shale beds in the Lower Member of the Vinini Formation, the greatest abundance of well preserved graptolites is found within the sandstone turbidite beds. These graptolites are uniquely preserved in full relief as opposed to being flattened on shale. It is interpreted based on fragmentation and species composition within the sandstone that the graptolites flourished in an upwelling zone on the continental margin and that as their remains accumulated on the underlying seafloor, were swept downslope in turbidity currents. </p><p> Graptolites were collected from 10 beds within the stratigraphic section and represent 33 taxa from 17 genera. There are no new taxa. All taxa are described, illustrated, and compared to other collections.</p>
2

A morphological and taxonomic revision of the Early Cretaceous Sapeornithidae (Aves| Pygostylia) of Liaoning Province, China

Pomeroy, Diana L. 18 April 2014 (has links)
<p> The Sapeomithidae are a unique and poorly understood clade of Early Cretaceous birds from the Jehol Group of Liaoning Province, China. Four species of sapeomithids are known: <i>Sapeornis chaoyangensis, Didactylornis jii, Sapeornis angus tis</i>, and <i>Shenshiornis primita</i>. <i>Omnivoropteryx sinousaorum</i> is allied with sapeomithids, although its nomenclature remains a source of contention. The validity of these taxa is challenged via an in-depth anatomical revision and morphometric analyses involving 18 specimens of sapeomithids, including the aforementioned holotypes. The results reveal that the only anatomical difference separating each species is size, implying a growth series trend among the specimens. This provides clear evidence that these species are junior synonyms of <i>Sapeornis chaoyangensis</i>. In addition, critical anatomical descriptions previously unknown for these specimens expand our knowledge of this clade, paving the way for future anatomical and phylogenetic studies of this enigmatic avian taxon.</p>

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