The University of Iowa Paleontology Repository maintains an extensive collection of Caribbean coral specimens. This study includes 285 specimens, of which approximately 75 are thin-sections of three previously identified Oligocene genera including: Montastraea Blainville, 1830 (=Orbicella Dana 1846), Antiguastrea Vaughan, 1919, and Agathiphyllia Reuss, 1864 (=Cyathomorpha Reuss, 1868). This study includes: photography of colony surfaces and thin-sections of representative specimens of each species, and the identification of the three Oligocene genera Montastraea, Antiguastrea, and Agathiphyllia to the species level. This study compared the collections with the agathiphyllid stratigraphic ranges in the Paleobiology Database, curated these specimens, and then entered the information into the database, SpecifyTM. These continued efforts aid in better understanding diagnostic morphologic characters of three genera: Antiguastrea, Agathiphyllia, and Montastraea. Two of the genera, Antiguastrea and Agathiphyllia, are extinct. Because the differences in morphology are subtle and not very well understood, previous biodiversity studies using the colony surface for correct species identification have been difficult and often inaccurate. Montastraea is further complicated by recent research that suggests it is polyphyletic and contains multiple species complexes, based on the combined use and creation of more morphological characters and on molecular phylogenetics. Additionally, this study assists with the understanding of the biodiversity of these Oligocene coral genera in the Caribbean region prior to the Plio-Pleistocene extinction event, and the evolutionary history of coral diversity in this region. Though there was an extinction event across the Caribbean, the locality species richness, using Fisher's α and Shannon's H, showed no significant differences between the Late Oligocene formations and the Early Miocene formations.

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No description available.

The extinct diprotodontoids were large bodied, browsing herbivorous marsupials most closely related to, among living marsupials, wombats. Referred to two families, Diprotodontidae and Palorchestidae, diprotodontoids are geographically and temporally widespread vombatimorphian taxa in Australian and New Guinean Cenozoic deposits. The most diverse diprotodontoid fauna recorded from any single region in Australia comes from Oligo-Miocene limestone deposits of the Riversleigh World Heritage Area, northwestern Queensland. In this thesis a new diprotodontoid genus and five new species are described from Riversleigh, as well as additional material from Riversleigh for the palorchestids Propalorchestes novaculacephalus and Pr. ponticulus and diprotodontids Nimbadon lavarackorum, Neohelos tirarensis, Neohelos stirtoni and Ngapakaldia bonythoni. A new vombatomorphian family, Maradidae, known from a single species at Riversleigh, is recognised as the sister-group of a vombatid-diprotodontoid clade. New abundant, exceptionally well-preserved cranial material of the zygomaturine Nimbadon lavarackorum enables characterisation of intraspecific variation and ontogenetic development. The results of these analyses have been used to discriminate species boundaries throughout this work. Consequently: Nimbadon whitelawi is now considered a junior synonym of Ni. lavarackorum; Nimbadon scottorrorum is a junior synonym of Neohelos tirarensis; and Bematherium angulum is a synonym of Ngapakaldia bonythoni. The new Riversleigh diprotodontoids clarify phylogenetic relationships within and between diprotodontoid families. The monophyly of both Palorchestidae and Diprotodontidae is strongly supported as is their union in the superfamily Diprotodontoidea. Monophyly of the Zygomaturinae and Diprotodontinae is not supported, primarily due to the unstable position of Alkwertatherium webbi as well as the high degree of homoplasy in cranial morphology of the more derived members of each subfamily. Overall phylogenetic and distribution patterns for diprotodontoids is generally consistent with current interpretations of Riversleigh's stratigraphy. Five diprotodontoid species allow direct biocorrelation with other Australian Tertiary mammal faunas. Riversleigh's basal System A deposits correlate with late Oligocene deposits of the Etadunna Formation of South Australia. Riversleigh's low-mid System C deposits correlate with the middle Miocene Bullock Creek Local Fauna of the Northern Territory. Riversleigh's high System C Jaw Junction and Encore Local Faunas contain diprotodontoid taxa antecedent to diprotodontoids of the late Miocene Alcoota Local Fauna of the Northern Territory.

The extinct diprotodontoids were large bodied, browsing herbivorous marsupials most closely related to, among living marsupials, wombats. Referred to two families, Diprotodontidae and Palorchestidae, diprotodontoids are geographically and temporally widespread vombatimorphian taxa in Australian and New Guinean Cenozoic deposits. The most diverse diprotodontoid fauna recorded from any single region in Australia comes from Oligo-Miocene limestone deposits of the Riversleigh World Heritage Area, northwestern Queensland. In this thesis a new diprotodontoid genus and five new species are described from Riversleigh, as well as additional material from Riversleigh for the palorchestids Propalorchestes novaculacephalus and Pr. ponticulus and diprotodontids Nimbadon lavarackorum, Neohelos tirarensis, Neohelos stirtoni and Ngapakaldia bonythoni. A new vombatomorphian family, Maradidae, known from a single species at Riversleigh, is recognised as the sister-group of a vombatid-diprotodontoid clade. New abundant, exceptionally well-preserved cranial material of the zygomaturine Nimbadon lavarackorum enables characterisation of intraspecific variation and ontogenetic development. The results of these analyses have been used to discriminate species boundaries throughout this work. Consequently: Nimbadon whitelawi is now considered a junior synonym of Ni. lavarackorum; Nimbadon scottorrorum is a junior synonym of Neohelos tirarensis; and Bematherium angulum is a synonym of Ngapakaldia bonythoni. The new Riversleigh diprotodontoids clarify phylogenetic relationships within and between diprotodontoid families. The monophyly of both Palorchestidae and Diprotodontidae is strongly supported as is their union in the superfamily Diprotodontoidea. Monophyly of the Zygomaturinae and Diprotodontinae is not supported, primarily due to the unstable position of Alkwertatherium webbi as well as the high degree of homoplasy in cranial morphology of the more derived members of each subfamily. Overall phylogenetic and distribution patterns for diprotodontoids is generally consistent with current interpretations of Riversleigh's stratigraphy. Five diprotodontoid species allow direct biocorrelation with other Australian Tertiary mammal faunas. Riversleigh's basal System A deposits correlate with late Oligocene deposits of the Etadunna Formation of South Australia. Riversleigh's low-mid System C deposits correlate with the middle Miocene Bullock Creek Local Fauna of the Northern Territory. Riversleigh's high System C Jaw Junction and Encore Local Faunas contain diprotodontoid taxa antecedent to diprotodontoids of the late Miocene Alcoota Local Fauna of the Northern Territory.

Through isotopic analysis of Viviparus lentus (V. lentus) a high resolution record of stepwise changes in δ18O and δ13C across the Eocene / Oligocene transition and Oi-1 glacial maximum has been produced for the continental Solent Group strata, Isle of Wight (UK). Comparison of this V. lentus δ18Ocarb. record with high resolution marine δ18Ocarb. records shows that similar isotopic shifts exist in the near coastal continental and marine realms. In order to calculate palaeotemperatures from this new continental record an investigation into the biology of modern Viviparus and its effect on the isotopic composition of its shell carbonate was undertaken. Experimental measurements of the 18O/16O isotope fractionation between the biogenic aragonite of Viviparus and its host freshwater were undertaken on samples derived from the Somerset Levels in order to generate a genus specific thermometry equation. The results from using this new Viviparus equation on fossil V. lentus shell fragments suggests that aquatic and terrestrial biota were being affected by climate change associated with the Late Eocene Event. This conicides with a decrease in mammal species richness in the Osborne Member, reaching its climax at the end of the Osborne / Seagrove Bay Members. This event is followed by a brief warming in the Bembridge Limestone which was marked by a within-Europe mammal turnover involving dispersal from the south and an increase in species richness, concurrent with this is an increase in size of Harrisichara gyrogonites. An additional investigation into seasonal isotopic variability using whole well preserved V. lentus specimens has also revealed a shift from tropical /subtropical to temperate climatic zones occurring before the Eocene /Oligocene boundary and Oi-1 glacial maximum. Overall the evidence provided by these investigations would suggest that climatic change was already in progress prior to the build up of glacial ice on Antarctica.

An abundant fossil record of the snake clade Scolecophidia exists in Europe; however, the minute snake is noticeably absent in reports about the North American Paleogene and Neogene. Presented here are four localities from Florida, USA, that contain scolecophidian remains older than the Pleistocene: Thomas Farm (late Early Miocene, Hemingfordian Land Mammal Age, LMA), Live Oak (Oligocene-Miocene transition, latest Arikareean LMA), White Springs 3B (late Arikareean LMA), and Brooksville 2 (Late Oligocene, middle Arikareean LMA). These remains extend their known existence by about 26. m.y. and are now the oldest reported scolecophidian remains in North America. Molecular evidence on extant scolecophidians concludes that these tiny snakes have a Gondwanan origin. Interestingly, the oldest record of a scolecophidian is from Europe (Belgium) and dates back to the middle Paleocene (MP 1-5). The earliest African record of the snake clade comes from the Paleocene-Eocene boundary in Morocco. The clade is apparently absent from Europe and Middle East deposits dating from the latest Eocene through to the latest Oligocene (MP 19-30) and to the Early Miocene (MN 4). A portion of this time is known as the booid 'Dark Period' which represents an apparent response to global aridization and cooling. Scolecophidians appear to re-emerge into the southern Eurasian record in the Early Miocene (MN 4) and become widely dispersed throughout Europe and Middle East. The fossil record of these minute snakes is largely absent in southern Asia and South America. It is possible that the current lack of a decent fossil scolecophidian record outside of Europe and Middle East is due mainly to a bias in the methodology to recover fossils; wet sieving sediments through. < 1.0. mm mesh is needed to recover the minuscule vertebrae.

An abundant fossil record of the snake clade Scolecophidia exists in Europe; however, the minute snake is noticeably absent in reports about the North American Paleogene and Neogene. Presented here are four localities from Florida, USA, that contain scolecophidian remains older than the Pleistocene: Thomas Farm (late Early Miocene, Hemingfordian Land Mammal Age, LMA), Live Oak (Oligocene-Miocene transition, latest Arikareean LMA), White Springs 3B (late Arikareean LMA), and Brooksville 2 (Late Oligocene, middle Arikareean LMA). These remains extend their known existence by about 26. m.y. and are now the oldest reported scolecophidian remains in North America. Molecular evidence on extant scolecophidians concludes that these tiny snakes have a Gondwanan origin. Interestingly, the oldest record of a scolecophidian is from Europe (Belgium) and dates back to the middle Paleocene (MP 1-5). The earliest African record of the snake clade comes from the Paleocene-Eocene boundary in Morocco. The clade is apparently absent from Europe and Middle East deposits dating from the latest Eocene through to the latest Oligocene (MP 19-30) and to the Early Miocene (MN 4). A portion of this time is known as the booid 'Dark Period' which represents an apparent response to global aridization and cooling. Scolecophidians appear to re-emerge into the southern Eurasian record in the Early Miocene (MN 4) and become widely dispersed throughout Europe and Middle East. The fossil record of these minute snakes is largely absent in southern Asia and South America. It is possible that the current lack of a decent fossil scolecophidian record outside of Europe and Middle East is due mainly to a bias in the methodology to recover fossils; wet sieving sediments through. < 1.0. mm mesh is needed to recover the minuscule vertebrae.

The marine silicon and carbon cycles are intrinsically linked by a unique group of primary producers; the diatoms. These siliceous-walled phytoplankton play a significant role in carbon export, making them a critical component of the global biological carbon pump with the power to affect climatic change. In this thesis, the silicon isotope composition (δ30Si) preserved in diatom opal is used together with the δ30Si of sponge opal, a powerful new proxy for deepwater silicic acid concentration, to document the Cenozoic Silicon cycle, shedding light on its role in carbon cycling and global climatic change. This study has developed a novel size-separation methodology to produce the first core top calibration of diatom δ30Si. The calibration demonstrates that diatom δ30Si exhibits a strong negative correlation with surface water silicic acid concentration, supportive of its application as a proxy for silicic acid utilisation. The refined method is used to produce a diatom δ30Si record, for the first time combined with sponge δ30Si, to gain insight into the Southern Ocean silicon cycle over one of the largest Cenozoic climatic shifts; the onset of Antarctic glaciation (~33.7 Ma). The two δ30Si records yield the first geochemical footprint to demonstrate that diatom proliferation, coincident with the onset of Antarctic circumpolar current flow, was a precursor event to the Eocene-Oligocene Transition. Diatoms are shown to have played a role in climate cooling through enhanced export and burial of organic carbon on the seafloor. The first long term reconstruction of silicic acid concentration in subsurface waters of the Southern Ocean, which spans the Late Eocene to the earliest Pliocene, provides new evidence that oceanic vertical mixing rates, coupled with the efficient removal of silicon from the surface by the diatoms, have been the most important factor in controlling the silicon chemistry of the ocean over the Cenozoic.

<p>Through the analysis of the stratigraphic and spatial distribution of organic walled dinoflagellate cysts (dinocysts) from climatologically and oceanographically key sites, this project aims to contribute to a better understanding of the Eocene-Oligocene (E/O) environmental changes and their timing. A central issue is to identify the global environmental changes which are responsible for the Eocene cooling and its underlying mechanisms with the focus on the Oligocene isotope-1 (Oi-1) event, thought to mark the onset of major Antarctic glaciation.</p><p>Two low-latitude sites were selected, Blake Nose (western North Atlantic) and Massignano (central Italy). For the first time a coherent taxonomy and biostratigraphy of dinocysts was established for the late Eocene at these latitudes. A high resolution correlation was established between the Massignano E/O Stratotype Section and the stratigraphically more extended ‘Massicore’. The composite section was used to analyse sea surface temperature (SST) change across the greenhouse-icehouse transition by means of dinocyst distribution.</p><p>At Massignano, the Oi-1 event was recognised both qualitatively and quantitatively. In the power spectrum of the SST_dino the ~100 and ~400 kyr eccentricity cycles may be distinguished and correlated with La04. When orbitally tuned, the E/O GSSP dates ~100 kyr older than the Oi-1 event. The boundary’s age could either be ~33.75 or ~34.1 Ma, both differ significantly from the ~33.9 Ma age in the GTS 2004.</p><p>Furthermore, when the data from the low-latitude sites were combined with extensive datasets from the Proto North Atlantic and adjacent regions, a suite of species sensitive to changes in SST was recognised. Their first and last occurrences reflect seven distinct phases of decreasing SSTs during the Middle Eocene to earliest Oligocene.</p><p>These results clearly indicate that atmospheric cooling together with higher frequency orbital forcing played a key role in the transition from the Greenhouse to the Icehouse world.</p>