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.

No description available.

Questions as to the tempo and mode of changes in faunal composition at the Triassic/Jurassic boundary remain unanswered. Inquiries are hampered by a general paucity of sections containing correlatable Late Triassic/Early Jurassic strata. Vertebrate fossil material from Cromhall Quarry, recovered as part of an extended project centered on Late Triassic fissure infillings in southwestern Britain, was organized into a biostratigraphic scheme in 1993. This scheme could prove important in correlating Late Triassic continental strata. The Cromhall data consists of taxonomic counts from individual Stratigraphic levels within a series of fissures. Level counts were sorted into a series of sequential sedimentary and faunal associations that rest on the assumption that significant differences in faunal composition occur between individual fissures, but do not exist between individual sedimentary strata within any one fissure. Before the biostratigraphic framework could be utilized, the actual degree of similarity between the fissure faunas had to be quantified and tested. The original database, and counts from newly processed material, were subjected to Principle Components and Cluster Analyses. The analyses suggest that the majority of stratigraphic levels within any one fissure contain faunas with very similar composition. Levels from fissures that are temporally sequential contain faunas that are somewhat similar in composition. Overlap, in faunas found in strata at the top and bottom of sequential fissures, can be detected. In addition, there is a trend toward increased presence of certain taxa in the younger levels. These results indicate that the biostratigraphic framework may be used to enhance Triassic-Jurassic boundary research. / Master of Science

The Triassic Cow Branch Formation of the Dan River Basin is host to a world-class lagerstätte deposit of exceptionally preserved insects, among other organisms. The lagerstätte occurs within a cyclic, lacustrine sedimentary succession, hypothesized to have been driven by Milankovitch climate forcing. Through an integrated sedimentological and geochemical investigation, I present evidence that the lagerstätte was deposited during a lake transgression, under intermittently anoxic and ferruginous conditions. Sedimentological evidence shows a deepening followed by shoaling through a broad fining and subsequent coarsening of the sedimentary units of the sequence. This transition in grain size occurs at the lagerstätte. Despite relatively quartz-rich sediments sourced to the basin, silica-content in the studied cycle is exceptionally low. The replacement of silica by the zeolite mineral analcime, coupled with primary dolomite precipitation suggests alkaline lake water. Geochemical evidence, including total organic carbon (TOC), pyrite sulfur and iron speciation data suggest anoxic, ferruginous waters. At the lagerstätte interval, TOC content increases significantly, coinciding with the presence of darker, more laminated sedimentary lithofacies. At the interval of the highest TOC content, a spike in pyrite sulfur content occurs; likely the result of slowed sedimentation. Organic carbon-to-pyrite sulfur ratios suggest however, that the lake water was sulfate-poor and the deep waters never became euxinic (anoxic, H2S-containing). Iron proxy data show that the studied portion of the Cow Branch Formation deposited under intermittent to persistent anoxic conditions. These data suggest a confluence of factors — lake transgression, combined with alkaline and anoxic, ferruginous water chemistry — created an ideal scenario that led to lagerstätte formation. / Master of Science

A review of all available surface and subsurface data on Triassic and Lower Jurassic rocks in northeastern Arizona has revealed the following information. The Moenkopi Formation, the Chinle Formation, and the Glen Canyon Group of Triassic and Early Jurassic age are present throughout most of the study area. These units form a sequence of continental and transitional marine origin that shows notable vertical and lateral facies changes. The Moenkopi Formation thickening west and northwestward with a maximum thickness of 134 meters. The unit comprises sandstone and shale, and shows more shaley facies westward. The Chinle Formation shows minimum thickness to the north and thickens toward east and south with a maximum thickness toward west. This unit dominantly consists of sandy shale, but contains more sandstone westward and north westward. The unit contains some limestone in north and northern region. The Chinle Formation is overlain by the Glen Canyon Group, which in ascending order comprises the Wingate Sandstone, the Moenave Formation, the Kayenta Formation, and the Navajo Sandstone. The Wingate Sandstone shows its maximum thickness in the central and southcentral region of the study area and thins west and eastward. This unit mainly comprises sandstone, particularly in its upper part. The Moenave Formation displays its zero thickness, in the eastern region and shows its maximum thickness, 198 meters, in the west-central part. The unit mainly consist of sandstone. The Kayenta Formation attains its greatest thickness, 204 meters, in the southwestern part of the region and thins east and northward. This formation contains high percentages of sandstone. Within the area of this study, the Navajo Sandstone is the thickest formation in the Glen Canyon Group. This unit almost entirely consist of sandstone pinches out toward the south and east, and displays its maximum thickness, 300 meters, northward.

In the Paria Plateau area of northern Arizona and southern Utah the Chinle formation of Upper Triassic age consists of a thick series of Ienticular sandstone, siltstone, claystone, and limestone. The series thins northwestward from about 900 feet at Lees Ferry, Ariz., to about 800 feet at Paria, Utah. Four members of the Chinle formation are recognized—1) the basal Shinarump member composed of conglomeratic sandstone and subordinate shale, 2) a unit, herein named the Lowery Spring member, composed of sandstone and mudstone, 3) the Petrified Forest member composed of bentonitic siltstone and claystone and thin sandstone, and 4) the Owl Rock member composed of cherty limestone and calcareous siltstone. Only the Petrified Forest member is present at all localities in the Paria Plateau area. The Shinarump member was deposited in topographic low areas on an erosion surface and its distribution is irregular. The Lowery Spring and Owl Rock members grade and pinch-out toward the northwest and are not present at Paria, Utah. The upper contact of the Chinle formation is locally unconformable. The three lowermost members were deposited on a broad, flat plain between the Cordilleran geosyncline and highlands to the southeast. In Owl Rock time the rising Cordilleran geanticline cut off the north-westward drainage of Chinle streams and a depositional basin trending southwest was formed.

No description available.

Paleomagnetic poles were obtained from the Chinle, Kayenta, Summerville, and Morrison Formations. Combined with paleomagnetic poles from the Moenave Formation, poles from the Chinle and Kayenta formations record ∼30 m.y. of North American apparent polar wander (APW) within a regional stratigraphic succession. During the Carnian and Norian stages of the Late Triassic, Chinle poles progress westward. During the Hettangian through Pliensbachian stages of the Early Jurassic, the pattern of APW changed to an eastward progression. Even after correction for 4° clockwise rotation of the Colorado Plateau, a sharp corner in the APW path (J1 cusp) is resolved near the pole from the Hettangian/Sinemurian (∼200 Ma) Moenave Formation (59.4°N; 59.2°E). The J1 cusp implies an abrupt change from counterclockwise rotation of Pangea prior to 200 Ma to clockwise rotation thereafter. Paleomagnetic poles obtained from the Summerville and Morrison formations are consistent with the Middle and Late Jurassic APW path described by the Corral Canyon and Glance Conglomerate paleomagnetic poles as well as a Late Jurassic Cusp (J2 cusp) in the APW path. The APW path described by the J2 cusp, a single Morrison Formation pole, and mid-Cretaceous paleomagnetic poles suggest from ∼150-126 Ma the North American plate experienced a minimum rate of motion of 0.93°/m.y. which is similar to rates calculated for the Late Triassic (0.73°/m.y.) and Jurassic (0.66°/m.y.). This rate is much lower than rates based on previous APW paths. Thermal demagnetization and data analysis indicate that within-site dispersion is an important criterion for selecting sites which retain a high unblocking-temperature, characteristic remanent magnetization (ChRM). This criterion was used to define at least three stratigraphically-distinct, antipodal polarity-zones within each member/formation, suggesting the ChRM was acquired soon after deposition. ChRMs from 15 to 22 sites in the Upper Shale Member of the Chinle Formation define an early Norian paleomagnetic pole position of 57.4°N, 87.8°E (K = 60, A₉₅ = 5.0°). ChRMs from 18 to 43 sites in the Owl Rock Member of the Chinle Formation define a middle Norian paleomagnetic pole position of 56.5°N, 66.4°E (K = 183, A₉₅ = 2.6°). ChRMs from 23 of 35 sites in the Kayenta Formation define a Pliensbachian pole position of 59.0°N, 66.6°E (K = 155, A₉₅ = 2.4°). ChRMs from 15 to 35 sites in the Summerville Formation define a late Callovian pole position of 53.8°N, 133.6°E (K = 25, A₉₅ = 7.5°). ChRMs from 15 sites in the Morrison Formation (9 from the study of Steiner and Helsley [1975]) define a single, ∼147 Ma, paleomagnetic pole position of 64.1°N, 152.4°E (K = 113, A₉₅ = 3.6°).

Fossil plants in the Upper Triassic Chinle Formation are preserved in fluvial channel, overbank, and lacustrine deposits. Plant-bearing units in these deposits are classified into seven types based on these depositional environments or subenvironments. Taphonomic characteristics of these assemblages, and of individual plant fossils within them, indicate that most plant fossils have either not been transported far from their growth sites or are preserved in situ. One particular deposit in the central part of Petrified Forest National Park preserves fossil plants in three associations: (1) allochthonous logs in basal lags in a channel-fill/lateral accretion deposits; (2) autochthonous horsetail trunks and parautochthonous horsetail leaves in a crevasse-splay deposits; and (3) parautochthonous and autochthonous cycadaceous, fern and other types of leaves, and erect and prostrate trunks in a paludal/distal splay deposits. Exposures of contemporaneous high-sinuosity channel and overbank deposits in this area enabled the reconstruction of the local paleogeography, paleohydrology, and paleoecology at a high resolution. Fossil plant assemblages of the Upper Triassic Chinle Formation are concentrated in the lower members of the formation. The lower part of the Chinle Formation was deposited in an incised valley system. Depositional, hydrological, and near-surface geochemical conditions in the incised valley system were conducive to preservation of terrestrial organic material, even though regional conditions were characterized by seasonal/monsoonal precipitation and groundwater conditions. Fossil plant assemblages preserved in these types of fully terrestrial incised valley-fills are taphonomically biased towards riparian wetland environments.

Os depósitos triássicos continentais do sul do Brasil abrigam uma grande diversidade de tetrápodes terrestres, incluindo terápsidos, rincossauros, rincocefálios e arcossauros, como pseudosúquios e dinossauromorfos. Inserida neste contexto, a Formação Santa Maria, de porção superior datada do Carniano superior, tem papel fundamental no entendimento da origem e irradiação inicial dos dinossauromorfos, pois abriga alguns dos mais antigos registros do grupo em todo mundo, incluindo vários fósseis de dinossauros. Atualmente, a fauna de dinossauromorfos desta unidade é representada por Ixalerpeton polesinensis, Teyuwasu barberenai, Staurikosaurus pricei, Saturnalia tupiniquim, Pampadromaeus barberenai, Buriolestes schultzi e Bagualosaurus agudoensis, enquanto para o Noriano da Formação Caturrita são conhecidos Guaibasaurus candelariensis, Unaysaurus tolentinoi e Sacisaurus agudoensis. Visando o melhor entendimento da diversidade de dinossauromorfos oriundos destes depósitos, foram descritos, no contexto dessa tese, diversos novos fósseis do grupo: ULBRA-PVT059, 280, LPRP/USP 0651, MCN PV 10007-8, 10026, 10027 e 10049. Adicionalmente, foi considerado o recente histórico de pesquisas sobre a origens dos dinossauros para examinar o impacto de novas descobertas e das diferentes hipóteses filogenéticas no entendimento dos padrões biogeográficos da irradiação dos dinossauros. ULBRA-PVT059 e 280 representam os holótipos de duas espécies de dinossauromorfos: Ixalerpeton polesinensis e Buriolestes schultzi. I. polesinensis é o primeiro lagerpetídeo descrito para o Brasil e o único no mundo que preserva elementos do crânio e do membro escapular. O material revela que algumas características antes inferidas como sinapomórficas para Dinosauria já estavam presentes em outros dinossauromorfos. B. schultzi é um sauropodomorfo, provável grupo-irmão dos demais representantes do grupo. Além disso, sua anatomia dentária e relações filogenéticas sugerem que os primeiros dinossauros, incluindo os sauropodomorfos, eram adaptados a faunivoria. LPRP/USP 0651 é o holótipo de uma nova espécie de dinossauro, Nhandumirim waldsangae, da Formação Santa Maria. Apesar de incompleto, as partes preservadas mostram que este se tratava de um indivíduo juvenil, mas que difere em vários aspectos dos demais dinossauros do Carniano, em especial daqueles provenientes dos mesmos níveis estratigráficos. As relações filogenéticas de N. waldsangae indicam que o novo táxon se trata de um dinossauro saurísquio não-sauropodomorfo, possivelmente afim aos terópodos. MCN PV 10007-8, 10026, 10027 e 10049 se tratam de materiais de dinossauros provenientes da localidade tipo de Sacisaurus agudoensis. Estes representam um sauropodomorfo morfologicamente mais semelhante a membros mais recentes do grupo do que aqueles do Carniano. Assim, correlações bioestratigráficas sugeridas pela presença destes sauropodomorfos indicam uma idade mais nova para a localidade tipo de S. agudoensis do que a das biozonas carnianas. As análises biogeográficas consistentemente otimizaram a porção sul do Gondwana como a área ancestral de Dinosauria, o mesmo se dando para clados mais inclusivos. Estes resultados mostram que a hipótese em questão é robusta mesmo com maior amostragem taxonômica e geográfica, e independentemente das hipóteses filogenéticas. Desta forma, é demonstrado que não há suporte para a hipótese da Laurásia representar a área ancestral dos dinossauros. / The Triassic deposits of southern Brazil harbor a great diversity of terrestrial tetrapods, including therapsids, rhynchocephalians, rhynchosaurs, and archosaurs like pseudosuchians and dinosauromorphs. In this context, the Carnian Santa Maria Formation is important for the understanding of the origins and early diversifications of Dinosauromorpha, as it bears one of the oldest records for the group worldwide, including some of the oldest dinosaurs. Its dinosauromorph fauna is currently represented by Ixalerpeton polesinensis, Staurikosaurus pricei, Saturnalia tupiniquim, Pampadromaeus barberenai, Buriolestes schultzi, Bagualosaurus agudoensis, and Teyuwasu barberenai. In comparison, the Norian Caturrita Formation have yielded Guaibasaurus candelariensis, Unaysaurus tolentinoi, and Sacisaurus agudoensis. In order to better understand the dinosauromorph diversity from these deposits, several new fossil remains were described as parts of this thesis: ULBRA-PVT 059, 280, LPRP/USP 0651, MCN PV 10007-8, 10026, 10027, and 10049. In addition, the last 20 years of research efforts on the origins of dinosaurs were compiled to investigate the impact of new discoveries and conflicting phylogenetic hypotheses on the biogeographic history of early dinosauromorphs. ULBRA-PVT 059 and 280 represent the holotypes of a lagerpetid dinosauromorph, Ixalerpeton polesinensis, and a sauropodomorph dinosaur, Buriolestes schultzi. I. polesinensis is the first lagerpetid described from Brazil and only worldwide that preserves skull and scapular limb remains, showing that some previously inferred dinosaur synapomorphies were already present in other early diverging dinosauromorphs. B. schultzi is found as the sister-group to all other sauropodomorphs. In addition, its tooth anatomy and phylogenetic position suggest that early dinosaurs, including sauropodomorphs, were adapted to faunivory. LPRP/USP 0651 is the holotype of a new dinosaur, Nhandumirim waldsangae, from the Santa Maria Formation. Although incomplete, the preserved parts show that it was a juvenile individual, but differing in several respects from other Carnian dinosaurs, especially those from the same stratigraphic levels. The phylogenetic relations of N. waldsangae suggest that the new taxon is a nonsauropodomorph saurischian dinosaur, possibly related to theropods. Dinosaur materials from the type-locality of Sacisaurus agudoensis (MCN PV 10007-8, 10026, 10027, and 10049) represent a sauropodomorph, more similar morphologically to later members of the group than to those of Carnian age. Hence, biostratigraphic correlations suggested by these sauropodomorphs indicate an age for the type-site of S. agudoensis younger than that of the Carnian biozones. Biogeographic analyzes consistently optimize southern Gondwana as the ancestral area for Dinosauria, and this is also the case for more inclusive clades. The results show that the South Gondwanan hypothesis for the origin of dinosaurs is robust even with increased taxonomic and geographic sampling, and independent of phylogenetic uncertainties. It is, therefore, demonstrated that there is no support for Laurassia as the ancestral area of dinosaurs.