It is now widely accepted that modern day birds originated from the clade Theropoda represented by bipedal carnivorous dinosaurs that thrived between the late Triassic and Cretaceous period. New research illustrates how the evolutionary assembly of the avian body plan began in these theropods with small fore limbs, large hind limbs and stiff tails, and progressed through a series of increasingly bird-like, transitional anatomical stages. There is also a great deal of homoplasy among dinosaurs however, or evolution of the same traits in distantly related groups, which makes it even more difficult to pinpoint the phylogenetic relationships among theropods. A limited fossil record and confusing temporal inconsistency has also led paleontologists and ornithologists alike to dismiss this crucial connection. They often attribute the origin of birds instead to a basal archosaur, ancestor to both dinosaurs and crocodilians. However the recent discoveries of feathered non-avian theropods, especially from the Late Jurassic and Early Cretaceous of Liaoning, China may finally lay the argument to rest. The scientific community has remained especially divided over to what degree feathers and other flight characteristics are present amongst the advanced theropods, and Dinosauria in general. Understanding this distinction helps separate each species into separate clades along the cloudy phylogenetic timeline as a function of feather development, and therefore offers insight into where they initially became functional for flight. Because fossils depicting defined integumental structures have been recently uncovered by the hundreds over the last 20 years, there is more evidence of this transition than ever. Through studies of theropod and avian physiology, we can gain more insight into the macroevolutionary principles and selective pressures that led dinosaurs to take to the sky.

Cyadeoidea medullara and C. cleavelandii, two new species of the genus Cycadeoidea, have been recovered from the Lower Cretaceous Cedar Mountain Formation of Utah. They have been described in histologic detail and relationships with similar species are set forth. Monoecism and pollination mechanisms have been discussed in connection with C. medullara. This data contributes to our knowledge of the diverse composition of Lower Cretaceous floras in Utah.

No description available.

No description available.

Several questions regarding the nature of extinction in the fossil record of marine invertebrates were investigated using statistical methods and familial diversity data. First, a series of analyses were performed to determine whether the magnitudes of mass extinctions were statistically distinguishable from the magnitudes of background extinctions. The expected proportions of familial extinction for each order in a stage (based on an estimate of the ordinal probability of familial extinction for each of 134 orders) were compared to the observed proportions of familial extinction in the stage using a simple X2 goodness-of-fit test. The results indicate that eight stages in the Phanerozoic had a statistically significant excess of extinction. A second set of X2 analyses was done using estimates of per taxon familial extinction rates for the orders, rather than familial extinction probabilities. The X2 tests resulted in four additional stages that contained a statistically significant surplus of familial extinction. To test the results further, a set of bootstrapping analyses was done for each of five different extinction metrics. Two stages, the Ashgillian and the Dzhulfian, had a statistically significant excess of extinction in both Xl analyses and in four out of five of the bootstrapping analyses. Two additional stages, the Guadelupian and the Maestrichtian, had a statistically significant magnitude of extinction in every analysis. Thus, the results provide strong support for the argument that mass extinctions comprise a distinct group of evolutionary phenomena. Familial extinction rates have declined from the early Phanerozoic to the Recent. Some have suggested that familial extinction rates have been constant through time within most major taxonomic groups and that the decline in familial extinction rates is the result of the successive elimination of groups with relatively high familial extinction rates (a process referred to as taxon sorting). A model of total familial extinction rates through time based on stationary probabilities of familial extinction within orders closely mimics the observed decline in total familial extinction rates supporting the taxon sorting hypothesis. Linear regressions of the familial extinction probabilities of orders versus the geologic time of both their first and their last occurrences suggest that the observed decline in extinction rates resulted from the early elimination of orders with characteristically high probabilities of extinction, and the later origination of orders with relatively low probabilities of extinction. In addition, a statistical analysis comparing the evolutionary volatility of extinct versus extant taxa suggests that extinct orders had greater volatility in their diversity histories which may have contributed to their early demise. The taxonomic selectivity of both background and mass extinctions was investigated using simple X2 analyses. The results suggest that familial extinction during mass extinctions was taxonomically more selective than extinction during background extinctions. In addition, the magnitude of familial extinction experienced by an order in a stage was compared to the familial extinction probability estimated for the order using the binomial theorem. Then, those orders that suffered an unusual excess of familial extinction during particular stratigraphic stages were separated from the remaining orders in the stage. The results suggest that sessile filter feeders (particularly those groups important in ancient reefs) and pelagic groups suffered the greatest during intervals of mass extinction. Finally, the potential relationship of familial diversity to both sea level and I7Sr/86Sr ratios was statistically examined using linear regression techniques. No statistically significant correlation was found between sea level and familial diversity. However, a significant correlation was discovered between diversity and I7Sr /86Sr ratios. Strontium ratios are believed to be an indirect measure of the aerial extent of exposed continental crust. Thus, the relationship between 17 Sr/86Sr ratios and diversity suggests that familial diversity has been a function of 1) the aerial extent of epeiric seas and 2) the amount of clastic material being supplied to these seas. The last factor could have affected familial diversity by restricting normally diverse, shallow carbonate environments. / Master of Science

The Monmouth and Brightseat Formations contain a rich and diverse dinoflagellate assemblage. Thirty-five genera and sixty-six species, of which two genera and eight species are new, are described in this study. The stratigraphic distribution of the taxa is summarized in Figure 4. The content of the assemblage changes suddenly at the Cretaceous-Tertiary boundary with thirteen species making the~r first appearance at or just above the boundary. Nineteen species cross the boundary and thirty-five species are restricted to the Cretaceous. The rather sudden change in the nature of the dinoflagellate assemblage at the boundary is interpreted by the author to indicate a paraconformable relationship between the Cretaceous and Paleocene sediments. The term paraconformity is used since there is little field evidence (a few pebbles, some lignite, and evidence of boring) indicating any extensive period of erosion at the boundary. / Master of Science

The coal-bearing Dakota Sandstone at Coal Canyon, Arizona, which is located in the western portion of the Black Mesa basin, has yielded abundant, diverse, and generally well-preserved spores, pollen, and microplankton. The formation is characterized by high frequencies of fern spores, especially striate spores belonging to the Schizaeaceae, and angiospermous pollen consisting primarily of simple tricolpate and tricolporate grains. Gymnospermous pollen is comparatively uncommon. The microflora assemblage contains many exclusively Cretaceous species previously reported from Australia, western Europe, Siberia, and other localities of North America. A microflora which compares closely with the Dakota assemblage occurs in the Woodbine strata of Oklahoma. On the basis of palynologic evidence, the age of the Dakota Sandstone at Coal Canyon, is interpreted as lowermost Upper Cretaceous (Cenomanian).

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Os gêneros de peixes fósseis Oshunia e Placidichthys são holósteos pertencentes à Ordem Ionoscopiformes e provenientes do Cretáceo Inferior do Brasil, das bacias do Araripe e de Tucano. No clado Ionoscopiformes sensu Grande & Bemis (1998) estão incluídas as famílias Ionoscopidae e Ophiopsidae, todavia as relações internas deste grupo ainda são duvidosas. Oshunia e Placidichthys fazem parte das famílias Ionoscopidae e Ophiopsidae, respectivamente, sendo o gênero Oshunia considerado como mono-específico (cf., O. brevis), enquanto que Placidichthys apresenta duas espécies nominais (cf., P. bidorsalis e P. tucanensis). Em função destas espécies terem sido descritas a partir de poucos espécimes, ainda existiam várias lacunas no conhecimento em relação as mesmas, como, por exemplo, a possibilidade da existência de outras espécies no gênero Oshunia e a falta de informações anatômicas, especialmente do crânio, da região occipital, dos ossos da face e da nadadeira caudal das espécies de Placidichthys. Outro ponto em aberto na literatura era a posição filogenética dos dois gêneros. Frente a estas questões, o objetivo da presente dissertação foi realizar uma revisão anatômica dos gêneros Oshunia e Placidichthys, a fim de ampliar o conhecimento anatômico e taxonômico acerca dos mesmos, além realizar uma análise filogenética da Ordem Ionoscopiformes, baseada em matrizes de caracteres existentes na literatura, para se obter um melhor posicionamento dessas espécies brasileiras. Em função da facilidade de acesso a material mexicano, também foram incluídos nesta revisão os gêneros Teoichthys e Tuetzalichthys provenientes do Cretáceo da Formação Tlayúa, estes também peixes fósseis holósteos pertencentes à Ordem Ionoscopiformes. Do ponto de vista taxonômico, não foi possível confirmar a existência de novas espécies para o gênero Oshunia, entretanto ficou clara a presença de uma nova espécie pertencente ao gênero mexicano Teoichthys. A presente revisão proporcionou uma série de novas informações sobre a anatomia destas espécies de Ionoscopiformes, tais como a descrição dos ossos circumorbitais e do teto craniano e uma reinterpretação acerca da nadadeira dorsal de Placidichthys bidorsalis, ou ainda sobre a forma do rostral de Teoichthys kallistos. Da mesma maneira, esta revisão também ofereceu novos dados para a construção de uma nova hipótese filogenética para Ionoscopiformes, a qual se mostrou consideravelmente distinta das hipóteses filogenéticas anteriores (cf., relações internas de Ionoscopidae e o posicionamento do gênero Teoichthys). O baixo suporte para grande parte dos clados torna evidente a fragilidade das hipóteses de relacionamento interno do clado Ionoscopiformes, bem como a necessidade de uma revisão mais aprofundada das outras espécies deste grupo e dos caracteres a serem utilizados em futuras análises filogenéticas. / The fossil genera Oshunia and Placidichthys are holosteans, belonging to the Order Ionoscopiformes, from the Early Cretaceous of the Araripe and Tucano basins in Brazil. Ionoscopiformes sensu Grande & Bemis (1998) includes the families Ionoscopidae and Ophiopsidae, however the inner relationships of this clade are still uncertain. Oshunia and Placidichthys belong to the families Ionoscopidae and Ophiopsidae, respectively, and while the genus Oshunia is considered to be monospecific (cf., O. brevis), Placidichthys presents two nominal species (cf., P. bidorsalis and P. tucanensis). Especially due to the fact that these species where described from just a few specimens, there were still several gaps on the knowledge about them, as for example, the possible existence of additional species from the genus Oshunia and the lack of anatomical information, notably from the skull roof, occipital region, check bones, and caudal fin of Placidichthys species. Another debatable matter was the phylogenetic position of these two genera. Given these issues, the objective of the present thesis was to make a revision of the genera Oshunia and Placidichthys, with the aim of increasing the anatomical and taxonomic knowledge about them, and also to make a phylogenetic analysis of Ionoscopiformes, based on data matrixes from the literature, in order to achieve a stronger hypothesis over the relationships of these Brazilian genera. Granted the easy access to Mexican specimens from the Cretaceous of the Tlayúa Formation, the genera Teoichthys and Quetzalichthys were also reviewed on the present work. From a taxomomical point of view, it was not possible to conclude over the existence of new species from the genus Oshunia, however it was evident the presence of a new species belonging to the Mexican genus Teoichthys. The present revision brought a series of new information over the anatomy of these Ionoscopiformes species, such as a first description of the circumorbital and skull roof bones and a reinterpretation over the dorsal fin of Placidichthys bidorsalis, or about the shape of the rostral bone of Teoichthys kallistos. Likewise, this revision also offered new data for the construction of a new phylogenetic hypothesis for Ionoscopiformes, which was considerably distinct from the anterior ones (cf., inner relationships of Ionoscopidae and the placement of the genus Teoichthys). The low support for many clades makes evident the fragility of the phylogenetic hypotheses of Ionoscopiformes, as well as the necessity of a more detailed revision of other species from this group and also of the characters to be used on future phylogenetic analyses.

The Early Cretaceous (Berriasian) Hope Bay flora is one of the most diverse assemblages from the Mesozoic of Antarctica. Collected in 1902 by the Swedish Antarctic Expedition of 1901-1903 from Hope Bay at the northern tip of the Antarctic Peninsula, and described in 1913 by T. G. Halle, it has served as a classic reference collection for Jurassic and Cretaceous southern hemisphere paleobotanical studies. Because the systematics of the flora were outdated by the enormous advances in our understanding of fossil plants during the last 70 years, it was in serious need of revision. This revision has reduced the number of taxa from 61 to 42 species. Newly erected species are Otozamites rowleyi, Kachchhia schopfii, Ticoa jeffersonii, and Araucaria antarctica. New combinations are Todites grahamii and Thinnfeldia salicifolia. The genera Kachchhia, Ticoa, and Weltrichia are new occurrences at Hope Bay. Represented in the flora are members of the Hepatophyta, Arthrophyta, Pteridophyta, Pteridospermophyta, Cycadophyta, Cycadeoidophyta, and Coniferophyta. Not surprisingly, when compared with other Gondwana floras, the Hope Bay flora shows the greatest similarity with other Antarctic floras. There is also a close affinity with the floras of South America and New Zealand. Taxonomic similarity between these floras is best explained by paleogeographic proximity. / text

Southern Alabama holds one of the world's most complete shallow shelf Cretaceous-Tertiary boundary sections. The boundary is exposed in a sequence of marl-limestone interbeds in a roadcut south-east of Braggs in Lowndes County, Alabama. Benthic foraminifera were extracted in 10cm intervals to obtain a high-resolution record of assemblage succession across this controversial boundary. A local sea level curve was then formulated using previous paleobathymetric foraminiferal assemblage models from the Gulf Coast and the Atlantic Coastal margin. Sea-level fluctuations thus evident have revealed a fourth-order cycle similar to those found by Briskin and Fluegeman (1990) with an average period of around 430 kyr through the Paleocene. This cycle includes a drop from outer slope to middle shelf conditions in the latest Cretaceous and a subsequent increase from inner shelf to outer shelf conditions in the earliest Paleocene. Within this cycle are several fifth-order cycles that are interpreted as having a periodicity of roughly 100 kyr. Sea-level cycles with Milankovitch frequencies occurring on an ice-free Paleocene Earth lend support to the concept of astronomical forcing of climate and thus sea-level. / Department of Geology