Post-Miocene fluvial and lacustrine units coristitute the valley fill of the San Pedro Valley, near Redington, Arizona. These sediments are relatively flat lying units deposited on older, deformed sediments, fault blocks of Tertiary volcanics, and erosion surfaces on Precambrian crystalline rocks. The sedimentary sequence is composed of silts, inudstone, sands, gravels, limestone, gypsum, diatomite, and pyroclastic units. Previous investigations have designated these lithologies one unit, the Gila Conglomerate. A recent study in the Mammoth area (Heindi, 1963) subdivided the Gila Conglomerate into the Quiburis formation, Sacaton formation and Pleistocene to Recent alluvial deposits. In the present study, this nomenclature was utilized, with a proposed subdivision of the Quiburis formation. Detailed mapping of the lithologic units indicate a lateral facies change within the Quiburis formation0 The conglomeritic member of the Quiburis formation interfingers with a central, fine-grained member, and the names Tres Alasnos, and Redington are proposed for these units. The age of the Quiburis formation is based on its stratigraphic position, and vertebrate fossils. The Qulbuns ovenlies tilted sediments containing Miocene fauna, and its upper portions contain fauna which have been assigned a middle to late Pliocene Age. The Sacaton formation was deposited on an erosion surface in the Quiburis in late Pliobene to early Pleistocene time; it was then entrenched and local, middle to late Pleistocene lacustnine units were deposited in the drainage pattern. Fresh water mollusks, horse and mammoth remains are present in the lacusbnine units. The Pleistocene lacustrine units were truncated by late Pleistocene terraces, and degradation proceeded to approximately 80 feet below the present floodplain. Aggradation occurred, to a level above the present floodplain, as attested by prehistoric hearths buried in river sediments, above the present stream gradient. Since 1880 the San Pedro River has begun another period of downcutting. The sedimentary deposits control the movement of ground water in the valley. Two hydrologic systems are present; a shallow water table system in the floodplain and river channel area, and an artesian system at 630- 1,200 feet below the valley floor in the northern portion of the study area. It is believed that deformed, pre- Miocene sedinentary units provide the source of recharge to the artesian system. Detailed mapping of the sedimentary units reveals a meandering central trough of the ancestoral San Pedro River. The contact between the Redington and Tres Alamos members of the Quiburis formation indicate the meander pattern, and its control by bedrock outcrop. Structural activity continued through Pliocene time, and is represented by north trending normal faults. Minor slump structures and small reverse faults are present in the Redington member of the Quiburis formation. A site survey, carried out during the field mapping, resulted in the location of nineteen archaeological sites. The sites range from preceramic Desert Culture to Salado and probably to later cultures such as the Apache. Older sites are peripheral to the valley axis, with more recent sites concentrated along the river. It appears that geologic-hydrologic factors controlling site location are: water sources; agricultural or gathering areas; quarry, or source material sites; and vantage points.

As pesquisas apresentadas nesta dissertação integram o projeto CNPq - PROANTAR 550352/02-3 \"Mudanças paleoclimáticas na Antártica durante o Cenozóico: o registro geológico terrestre\", que estuda os depósitos cenozóicos da ilha Rei George em busca elucidação do histórico ambiental e climático desta região antártica. A evolução dos padrões de circulação marinha e atmosférica no Hemisfério Sul ocorreu em resposta ao isolamento geográfico e térmico da Antártica, resultado de sua separação da Austrália, no limite Eoceno/Oligoceno, e da América do Sul, no final do Oligoceno. Sob este aspecto, o estudo de organismos fósseis registrados nos depósitos cenozóicos da Antártica contribui para o entendimento das evoluções biológicas e ambientais ocorridas concomitantemente às mudanças paleogeográficas, oceanográficas e climáticas na região ao longo do Cenozóico. Frente à dificuldade de acesso, demanda logística e extensa cobertura de gelo, apenas uma pequena porção do registro geológico da Antártica está acessível para pesquisa. Afloramentos da ilha Rei George registram as mudanças climáticas e ambientais ocorridas do Oligoceno ao Mioceno, incluindo evidências do primeiro evento de glaciação perene no oeste do continente (Oligoceno). A despeito da abundância de fósseis nos estratos cenozóicos da ilha, são poucos os trabalhos taxonômicos com descrição sistemática detalhada de bivalves fósseis. O primeiro módulo do presente estudo apresenta a descrição taxonômica de invertebrados de depósitos cenozóicos aflorantes em duas localidades da ilha Rei George, Antártica ocidental. Da Formação Cape Melville (Mioceno), península Melville, foram descritos sete táxons de bivalves, incluindo seis espécies novas. Da Formação Polonez Cove (Oligoceno), Pico Vauréal, uma região previamente inexplorada paleontologicamente, foram descritos sete táxons de invertebrados (bivalves, braquiópodes, tubos de serpulídeos, briozoários e fragmentos de equinodermes), incluindo duas espécies novas. O segundo módulo corresponde à reunião dos gêneros de bivalves registrados em depósitos cenozóicos da Antártica. A análise do registro apontou para o conhecimento bastante incipiente sobre a diversidade de bivalves antárticos ao longo do Cenozóico. Além disso, a comparação entre gêneros de bivalves cenozóicos registrados na Antártica e Nova Zelândia revelou que a maior parte dos gêneros compartilhados está registrada em depósitos eocênicos, o que suporta o isolamento geográfico da Antártica e a redução do intercâmbio faunístico entre a Antártica e regiões periféricas após o Oligoceno. A análise do registro sugeriu um evento de dispersão intenso durante o Eoceno, e pequenos pulsos de dispersão após o Oligoceno. O padrão de distribuição dos táxons concorda parcialmente com as reconstituições de paleocorrentes disponíveis na literatura. A dispersão durante o Eoceno teria ocorrido da Antártica para a Nova Zelândia na direção do Atlântico para o Pacífico. Este evento de dispersão concorda com a hipótese de existência de conexões marinhas de plataforma rasa entre o oeste e o leste da Antártica (\"Passagem de Shackleton\") e da província Weddeliana do final do Cretáceo ao Eoceno. Os eventos de dispersão pósoligocênicos teriam ocorrido durante e após o estabelecimento da Corrente Circum-Antártica, não mais pela \"Passagem de Shackleton\", mas margeando a Antártica pelas bordas ocidental atlântica e oriental em direção à Nova Zelândia. A análise do registro dos bivalves cenozóicos da Antártica também concorda com a hipótese de glaciação perene a partir do início do Oligoceno na região leste do continente, e na metade do Oligoceno na região oeste, com temperaturas mais amenas que as observadas atualmente. / The research presented in this dissertation comprised part of the CNPq - PROANTAR Project 550352/02-3 \"Mudanças paleoclimáticas na Antártica durante o Cenozóico: o registro geológico terrestre\", which studies Cenozoic deposits from King George Island in order to elucidate the environmental and climatic Cenozoic histories of this Antarctic region. Cenozoic evolution of marine and atmospheric circulation in the Southern Hemisphere occurred in response to the geographic and thermal isolation of Antarctica, which resulted from the separation of Antarctica from Australia, around Eocene/Oligocene boundary, and from South America, during the late Oligocene. Thus, study of fossil organisms from Antarctic Cenozoic deposits contributes to the understanding of biological and environmental evolutions that accompanied paleogeographic, oceanographic and climatic changes during the Cenozoic. As a result of the difficult access, logistic demand and extensive ice cover, only a small part of the Cenozoic Antarctic record is available for study. King George Island records climatic and environmental changes from the Oligocene to the Miocene, including evidence of the first full-scale glaciation (Oligocene) of West Antarctica. Despite the abundance of fossils in Cenozoic deposits of the island, taxonomic studies with detailed systematic descriptions of bivalves are very rare. The first section of this work consists of taxonomic descriptions of invertebrates from Cenozoic deposits cropping out in two localities of King George Island, West Antarctica. Seven taxa of bivalves, including six new species were described from the Cape Melville Formation (Miocene), at Melville Peninsula. Seven taxa of invertebrates (bivalves, brachiopods, serpulid tubes, bryozoans, and echinoderm fragments) were described from the Polonez Cove Formation (Oligocene), at Vauréal Peak, a site previously unexplored paleontologically. The second section presents the results of a survey of the Cenozoic fossil record of Antarctic bivalves. The analysis of the fossil record confirmed that the current knowledge about the Cenozoic diversity of the group is very scarce. Moreover, comparison of Cenozoic bivalve genera from Antarctica and New Zealand showed that the greatest number of shared taxa is recorded in Eocene deposits. This finding supports the geographic isolation of Antarctic and the drop in faunal interchange between Antarctica and periphery after the Oligocene. Analysis of the fossil record suggested an intensive dispersal event during the Eocene, and restricted pulses of dispersal from the Oligocene onwards. The distribution pattern of taxa provides partial support for available reconstructions of marine currents. Eocene dispersal would have occurred from Antarctica to New Zealand in Atlantic-Pacific direction. This dispersal event is consistent with the hypothesis of shallow marine connections between West and East Antarctica (\"Shackleton Seaway\"), as well of the existence of the Weddellian Province from the Late Cretaceous to the Eocene. Dispersal events following the Oligocene would have occurred during and after the establishment of the Circum-Antarctic Current, along the West-Atlantic and East margins of Antarctica towards New Zealand, and no longer through \"Shackleton Seaway\". These analyses also support the hypothesis of full-scale glaciation in West Antarctica from the early Oligocene onwards, and in East Antarctica since the mid-Oligocene, with warmer temperatures than today.

Trabalhos objetivando a tafonomia de concentrações fossilíferas geradas em ambiente glacial ou periglacial são raros. Neste contexto, a presente dissertação realizou a caracterização tafonômica das concentrações fossilíferas da Formação Cape Melville, Grupo Moby Dick (Mioceno Inferior), Ilha Rei George, Antártica, tendo em vista a elucidação da gênese destes depósitos. Para tanto, dados relativos a um total de 534 espécimes foram obtidos nas camadas ricamente fossilíferas das quatro seções, denominadas Pingüineira (PRS), Hard Ground (HGS), Chaminé (CS) e Lava Crag (LCS), levantadas no topo da Península Melville entre Janeiro e Fevereiro de 2003. Destas, apenas a Seção PRS apresenta duas camadas fossilíferas distintas (PRS-C1 e PRS-C2). A fauna estudada é composta predominantemente por restos de moluscos bivalves. Restos menos abundantes de corais, caranguejos, gastrópodes e braquiópodes, além de icnofósseis, também estão presentes. A análise da composição taxonômica, ecológica e tafonômica permitiu identificar semelhanças entre as Seções PRS e HGS e entre as Seções CS e LCS. As seções PRS e HGS são compostas dominantemente por bivalves depositívoros da infauna rasa (Ennucula frigida, Enncula musculosa e Yoldia peninsularis), preservados preferencialmente com as valvas articuladas fechadas, porém fora da posição de vida, indicando remobilização da fauna pré-soterramento; a ausência de sinais de fragmentação, abrasão e incrustação indica que os bioclastos não foram afetados por processos bioestratinômicos químicos, físicos ou biológicos intensos. A ocorrência de bioclastos piritizados na Seção HGS é interpretada como resultante da decomposição dos organismos soterrados, ainda vivos, em ambiente anóxico. As assembléias das seções CS e LCS são constituídas dominantemente por bivalves suspensívoros da infauna profunda (Neilo (N.) rongelii), preservados preferencialmente com as valvas desarticuladas, indicando que os processos bioestratinômicos físicos foram mais atuantes, sendo, no entanto, raros os sinais de fragmentação e de outras assinaturas tafonômicas como incrustação e bioerosão. As valvas desarticuladas estão preservadas preferencialmente com a convexidade voltada para baixo indicando que os bioclastos foram colocados em suspensão e redepositados fora da posição de maior estabilidade hidrodinâmica; a orientação em planta destes bioclastos exibe direção preferencial, indicando atuação de correntes fracas e um maior tempo de exposição na interface água/sedimento; a ocorrência de raros restos de bivalves suspensívoros escavadores da infauna profunda (Panopea (P.) cf. P. regularis) e de caranguejos (Antarctidromia inflata) preservados em posição de vida é indicativa de que esta comunidade foi soterrada in situ por sedimentos em suspensão que trouxeram a tanatocenose de valvas desarticuladas. Os resultados obtidos no presente estudo reiteram a importância dos estudos tafonômicos e paleoecológicos no entendimento da dinâmica deposicional do passado, contribuindo com um grande conjunto de dados úteis na caracterização de ambientes glaciais e periglaciais. / Works focusing on the taphonomy of fossil concentrations generated in glacial or periglacial environment are rare. In this context, the present dissertation carried out the taphonomic characterization of the fossil concentrations of the Cape Melville Formation, Moby Dick Group (Lower Miocene), King George Island, Antarctica, in order to elucidate the genesis of these deposits. To this end, data relative to a total of 534 specimens were obtained in the richly fossil layers of the four sections, called Pingüineira (PRS), Hard Ground (HGS), Chaminé (CS) and Lava Crag (LCS), investigated at the top of the Melville Peninsula between January and February of 2003. Of these, only the PRS Section presents two distinct fossil layers (PRS-C1 and PRS-C2). The studied fauna is mainly composed of remains of bivalve clams. Less abundant remains of corals, crabs, gastropods and brachiopods, as well as trace fossils, also are present. Taxonomic, ecological and taphonomic analyses allowed similarities to be identified between PRS and HGS and CS and LCS. PRS and HGS Sections are dominantly composed by shallow infaunal deposit-feeding bivalves (Ennucula frigida, Enncula musculosa Yoldia peninsularis), preserved preferentially with closed articulated valves, however out of life position, indicating remobilized fauna; the absence of signs of spalling, abrasion and incrustation indicates that the bioclasts were not affected by intense chemical, physical or biological bioestratinomic processes. The occurrence of pyritized bioclasts in HGS is interpreted as the result of decomposition of the entombed organisms, still alive, in an anoxic environment. The assemblages of CS and LCS Sections are dominantly constituted by deep infaunal suspension-feeding bivalves (Neilo (N.) rongelii), preserved preferentially with disarticulated valves, indicating that the physical biostratinomic processes were more operative; however there are few signs of spalling or other taphonomic signatures such as incrustation and bioerosion. Disarticulated valves are preferentially preserved convex down indicating that bioclasts were placed in suspension and redeposited in a position other than that of greatest hydrodynamic stability; the orientation of these bioclasts in plan view shows a preferential direction, indicating weak currents and a longer time of exposition at the water/sediment interface; the occurrence of rare remains of deep infaunal suspension-feeding bivalves (Panopea (P.) cf. P. regularis) and crabs (Antarctidromia inflata) preserved in life position is indicative that this community was entombed in situ by sediments in suspension that brought the thanatocenosis of disarticulated valves. The results obtained in the present study reiterate the importance of taphonomic and paleoecological studies for the understanding of the depositional dynamics of the past and contribute a great number of data useful in the characterization of glacial and periglacial environments.

As pesquisas apresentadas nesta dissertação integram o projeto CNPq - PROANTAR 550352/02-3 \"Mudanças paleoclimáticas na Antártica durante o Cenozóico: o registro geológico terrestre\", que estuda os depósitos cenozóicos da ilha Rei George em busca elucidação do histórico ambiental e climático desta região antártica. A evolução dos padrões de circulação marinha e atmosférica no Hemisfério Sul ocorreu em resposta ao isolamento geográfico e térmico da Antártica, resultado de sua separação da Austrália, no limite Eoceno/Oligoceno, e da América do Sul, no final do Oligoceno. Sob este aspecto, o estudo de organismos fósseis registrados nos depósitos cenozóicos da Antártica contribui para o entendimento das evoluções biológicas e ambientais ocorridas concomitantemente às mudanças paleogeográficas, oceanográficas e climáticas na região ao longo do Cenozóico. Frente à dificuldade de acesso, demanda logística e extensa cobertura de gelo, apenas uma pequena porção do registro geológico da Antártica está acessível para pesquisa. Afloramentos da ilha Rei George registram as mudanças climáticas e ambientais ocorridas do Oligoceno ao Mioceno, incluindo evidências do primeiro evento de glaciação perene no oeste do continente (Oligoceno). A despeito da abundância de fósseis nos estratos cenozóicos da ilha, são poucos os trabalhos taxonômicos com descrição sistemática detalhada de bivalves fósseis. O primeiro módulo do presente estudo apresenta a descrição taxonômica de invertebrados de depósitos cenozóicos aflorantes em duas localidades da ilha Rei George, Antártica ocidental. Da Formação Cape Melville (Mioceno), península Melville, foram descritos sete táxons de bivalves, incluindo seis espécies novas. Da Formação Polonez Cove (Oligoceno), Pico Vauréal, uma região previamente inexplorada paleontologicamente, foram descritos sete táxons de invertebrados (bivalves, braquiópodes, tubos de serpulídeos, briozoários e fragmentos de equinodermes), incluindo duas espécies novas. O segundo módulo corresponde à reunião dos gêneros de bivalves registrados em depósitos cenozóicos da Antártica. A análise do registro apontou para o conhecimento bastante incipiente sobre a diversidade de bivalves antárticos ao longo do Cenozóico. Além disso, a comparação entre gêneros de bivalves cenozóicos registrados na Antártica e Nova Zelândia revelou que a maior parte dos gêneros compartilhados está registrada em depósitos eocênicos, o que suporta o isolamento geográfico da Antártica e a redução do intercâmbio faunístico entre a Antártica e regiões periféricas após o Oligoceno. A análise do registro sugeriu um evento de dispersão intenso durante o Eoceno, e pequenos pulsos de dispersão após o Oligoceno. O padrão de distribuição dos táxons concorda parcialmente com as reconstituições de paleocorrentes disponíveis na literatura. A dispersão durante o Eoceno teria ocorrido da Antártica para a Nova Zelândia na direção do Atlântico para o Pacífico. Este evento de dispersão concorda com a hipótese de existência de conexões marinhas de plataforma rasa entre o oeste e o leste da Antártica (\"Passagem de Shackleton\") e da província Weddeliana do final do Cretáceo ao Eoceno. Os eventos de dispersão pósoligocênicos teriam ocorrido durante e após o estabelecimento da Corrente Circum-Antártica, não mais pela \"Passagem de Shackleton\", mas margeando a Antártica pelas bordas ocidental atlântica e oriental em direção à Nova Zelândia. A análise do registro dos bivalves cenozóicos da Antártica também concorda com a hipótese de glaciação perene a partir do início do Oligoceno na região leste do continente, e na metade do Oligoceno na região oeste, com temperaturas mais amenas que as observadas atualmente. / The research presented in this dissertation comprised part of the CNPq - PROANTAR Project 550352/02-3 \"Mudanças paleoclimáticas na Antártica durante o Cenozóico: o registro geológico terrestre\", which studies Cenozoic deposits from King George Island in order to elucidate the environmental and climatic Cenozoic histories of this Antarctic region. Cenozoic evolution of marine and atmospheric circulation in the Southern Hemisphere occurred in response to the geographic and thermal isolation of Antarctica, which resulted from the separation of Antarctica from Australia, around Eocene/Oligocene boundary, and from South America, during the late Oligocene. Thus, study of fossil organisms from Antarctic Cenozoic deposits contributes to the understanding of biological and environmental evolutions that accompanied paleogeographic, oceanographic and climatic changes during the Cenozoic. As a result of the difficult access, logistic demand and extensive ice cover, only a small part of the Cenozoic Antarctic record is available for study. King George Island records climatic and environmental changes from the Oligocene to the Miocene, including evidence of the first full-scale glaciation (Oligocene) of West Antarctica. Despite the abundance of fossils in Cenozoic deposits of the island, taxonomic studies with detailed systematic descriptions of bivalves are very rare. The first section of this work consists of taxonomic descriptions of invertebrates from Cenozoic deposits cropping out in two localities of King George Island, West Antarctica. Seven taxa of bivalves, including six new species were described from the Cape Melville Formation (Miocene), at Melville Peninsula. Seven taxa of invertebrates (bivalves, brachiopods, serpulid tubes, bryozoans, and echinoderm fragments) were described from the Polonez Cove Formation (Oligocene), at Vauréal Peak, a site previously unexplored paleontologically. The second section presents the results of a survey of the Cenozoic fossil record of Antarctic bivalves. The analysis of the fossil record confirmed that the current knowledge about the Cenozoic diversity of the group is very scarce. Moreover, comparison of Cenozoic bivalve genera from Antarctica and New Zealand showed that the greatest number of shared taxa is recorded in Eocene deposits. This finding supports the geographic isolation of Antarctic and the drop in faunal interchange between Antarctica and periphery after the Oligocene. Analysis of the fossil record suggested an intensive dispersal event during the Eocene, and restricted pulses of dispersal from the Oligocene onwards. The distribution pattern of taxa provides partial support for available reconstructions of marine currents. Eocene dispersal would have occurred from Antarctica to New Zealand in Atlantic-Pacific direction. This dispersal event is consistent with the hypothesis of shallow marine connections between West and East Antarctica (\"Shackleton Seaway\"), as well of the existence of the Weddellian Province from the Late Cretaceous to the Eocene. Dispersal events following the Oligocene would have occurred during and after the establishment of the Circum-Antarctic Current, along the West-Atlantic and East margins of Antarctica towards New Zealand, and no longer through \"Shackleton Seaway\". These analyses also support the hypothesis of full-scale glaciation in West Antarctica from the early Oligocene onwards, and in East Antarctica since the mid-Oligocene, with warmer temperatures than today.

No description available.

No description available.

Os crocodilianos, como são chamados vernacularmente os membros de Crocodylia, tem uma origem mesozoica, datando do Campaniando da América do Norte e Europa. No final deste período, ou no início do Paleoceno, um grupo de aligatoroídeos dispersou para a América do Sul, dando origem a um dos dois grupos principais de Alligatoridae, os Caimaninae. Este grupo é pobremente registrado no continente durante todo o Paleogeno, apesar de ser o único grupo de Crocodylia presente na região durante este período. O Mioceno é marcado pela maior diversidade de Caimaninae, considerando qualquer época ou lugar. Além disso, a diversidade miocênica é constituída também por crocodilídeos e gavialoídeos, até então não registrados para o continente sul-americano. Este cenário muda na passagem para o Plioceno, quando estes últimos desaparecem por completo na América do Sul, e os caimaníneos, apesar de continuarem existindo, não deixaram registro fóssil. Os crocodilídeos miocênicos foram extintos no continente, mas é nesta Época que o gênero Crocodylus sofreu dispersão transoceânica da África para as Américas. O Pleistoceno é marcado por um registro fóssil fragmentário, apesar de serem encontrados crocodilídeos em diversas localidades por toda a América do Sul. No Holoceno são encontradas evidências de interação entre Homo sapiens e crocodilianos, representadas em pinturas rupestres e restos zooarqueológicos. Apesar da grande quantidade de fósseis já coletados e estudados, o conhecimento sobre o registro fóssil de Crocodylia na América do Sul está muito aquém do desejado. A presente Tese é formada por 5 artigos sobre novos registros de crocodilianos fósseis sulamericano. O primeiro artigo descreve uma nova espécie de Crocodylus, o primeiro registro para a América do sul. O segundo artigo extende a diagnose de Caiman brevirostris através da análise de um novo espécime, e realiza uma análise cladística dos Jacarea. O terceiro artigo apresenta os primeiros registros de crocodilianos para o Pleistoceno da Venezuela, descrevendo também uma nova espécie de Caiman. O quarto artigo reporta uma nova espécie pliocênica de Crocodylus, a mais antiga para as Américas. Além disso, a espécie é táxon irmão das espécies recentes de crocodilos do Novo Mundo. O quinto e último artigo descreve uma nova espécie de Eocaiman, para ao Paleoceno da Bacia de Itaboraí. Através destes novos registros, esta Tese contribui para o conhecimento sobre os crocodilianos da América do Sul. / The crocodylians, as the members of the Crocodylia are vernacularly called, have an early origin, dating back to the Late Cretaceous. At the end of this period, or at the beginning of the Paleocene, a group of alligatoroids dispersed to South America, giving rise to one of the main groups within Alligatoridae, Caimaninae. This group is poorly recorded in this continent during the Paleogene, despite the fact that it was the only Crocodylia group in the region during this period. The Miocene is known for the greatest Caimaninae diversity, considering anytime or anywhere. Besides, the Miocene diversity is also formed by crocodylids and gavialoids, until then not recorded in South America. This scenario changed when passing to the Pliocene, when the crocodylids and gavialoids disappeared in South America, and the caimanines, although remained, they left no fossil record. The Miocene crocodylids were extinct in the continent, but was in that time when the genus Crocodylus dispersed from Africa to the Americas. The Pleistocene is known by a fragmentary fossil record, although being recorded a number of localities all over the South America. In the Holocene, interaction between Homo sapiens and crocodilians are found, represented by rock art and zooarcheological remains. In spite of the great number of collected and studied fossils, the knowledge on the Crocodylia Fossil Record is beneath expectations, but the perspectives for research are optimist. This thesis has 5 articles about new records of fossil crocodilians from South America. The first describes a new species of Crocodylus, the first for South America. The second extends the Caiman brevirostris diagnosis through a new specimen, and performs a cladistics analysis of the Jacarea. The third presents the first Pleistocene crocodilians from Venezuela, describing a new species of Caiman. The forth article reports a new Pliocene species of Crocodylus, the oldest record in the Americas. Also, this taxon is the sister group to the recent New World crocodiles. At last, the fifth article describes a new species of Eocaiman, from the Paleocene of Itaboraí basin. Through these new fossils, this Thesis contributes to the knowledge on the fossil crocodilians from South America.

Trabalhos objetivando a tafonomia de concentrações fossilíferas geradas em ambiente glacial ou periglacial são raros. Neste contexto, a presente dissertação realizou a caracterização tafonômica das concentrações fossilíferas da Formação Cape Melville, Grupo Moby Dick (Mioceno Inferior), Ilha Rei George, Antártica, tendo em vista a elucidação da gênese destes depósitos. Para tanto, dados relativos a um total de 534 espécimes foram obtidos nas camadas ricamente fossilíferas das quatro seções, denominadas Pingüineira (PRS), Hard Ground (HGS), Chaminé (CS) e Lava Crag (LCS), levantadas no topo da Península Melville entre Janeiro e Fevereiro de 2003. Destas, apenas a Seção PRS apresenta duas camadas fossilíferas distintas (PRS-C1 e PRS-C2). A fauna estudada é composta predominantemente por restos de moluscos bivalves. Restos menos abundantes de corais, caranguejos, gastrópodes e braquiópodes, além de icnofósseis, também estão presentes. A análise da composição taxonômica, ecológica e tafonômica permitiu identificar semelhanças entre as Seções PRS e HGS e entre as Seções CS e LCS. As seções PRS e HGS são compostas dominantemente por bivalves depositívoros da infauna rasa (Ennucula frigida, Enncula musculosa e Yoldia peninsularis), preservados preferencialmente com as valvas articuladas fechadas, porém fora da posição de vida, indicando remobilização da fauna pré-soterramento; a ausência de sinais de fragmentação, abrasão e incrustação indica que os bioclastos não foram afetados por processos bioestratinômicos químicos, físicos ou biológicos intensos. A ocorrência de bioclastos piritizados na Seção HGS é interpretada como resultante da decomposição dos organismos soterrados, ainda vivos, em ambiente anóxico. As assembléias das seções CS e LCS são constituídas dominantemente por bivalves suspensívoros da infauna profunda (Neilo (N.) rongelii), preservados preferencialmente com as valvas desarticuladas, indicando que os processos bioestratinômicos físicos foram mais atuantes, sendo, no entanto, raros os sinais de fragmentação e de outras assinaturas tafonômicas como incrustação e bioerosão. As valvas desarticuladas estão preservadas preferencialmente com a convexidade voltada para baixo indicando que os bioclastos foram colocados em suspensão e redepositados fora da posição de maior estabilidade hidrodinâmica; a orientação em planta destes bioclastos exibe direção preferencial, indicando atuação de correntes fracas e um maior tempo de exposição na interface água/sedimento; a ocorrência de raros restos de bivalves suspensívoros escavadores da infauna profunda (Panopea (P.) cf. P. regularis) e de caranguejos (Antarctidromia inflata) preservados em posição de vida é indicativa de que esta comunidade foi soterrada in situ por sedimentos em suspensão que trouxeram a tanatocenose de valvas desarticuladas. Os resultados obtidos no presente estudo reiteram a importância dos estudos tafonômicos e paleoecológicos no entendimento da dinâmica deposicional do passado, contribuindo com um grande conjunto de dados úteis na caracterização de ambientes glaciais e periglaciais. / Works focusing on the taphonomy of fossil concentrations generated in glacial or periglacial environment are rare. In this context, the present dissertation carried out the taphonomic characterization of the fossil concentrations of the Cape Melville Formation, Moby Dick Group (Lower Miocene), King George Island, Antarctica, in order to elucidate the genesis of these deposits. To this end, data relative to a total of 534 specimens were obtained in the richly fossil layers of the four sections, called Pingüineira (PRS), Hard Ground (HGS), Chaminé (CS) and Lava Crag (LCS), investigated at the top of the Melville Peninsula between January and February of 2003. Of these, only the PRS Section presents two distinct fossil layers (PRS-C1 and PRS-C2). The studied fauna is mainly composed of remains of bivalve clams. Less abundant remains of corals, crabs, gastropods and brachiopods, as well as trace fossils, also are present. Taxonomic, ecological and taphonomic analyses allowed similarities to be identified between PRS and HGS and CS and LCS. PRS and HGS Sections are dominantly composed by shallow infaunal deposit-feeding bivalves (Ennucula frigida, Enncula musculosa Yoldia peninsularis), preserved preferentially with closed articulated valves, however out of life position, indicating remobilized fauna; the absence of signs of spalling, abrasion and incrustation indicates that the bioclasts were not affected by intense chemical, physical or biological bioestratinomic processes. The occurrence of pyritized bioclasts in HGS is interpreted as the result of decomposition of the entombed organisms, still alive, in an anoxic environment. The assemblages of CS and LCS Sections are dominantly constituted by deep infaunal suspension-feeding bivalves (Neilo (N.) rongelii), preserved preferentially with disarticulated valves, indicating that the physical biostratinomic processes were more operative; however there are few signs of spalling or other taphonomic signatures such as incrustation and bioerosion. Disarticulated valves are preferentially preserved convex down indicating that bioclasts were placed in suspension and redeposited in a position other than that of greatest hydrodynamic stability; the orientation of these bioclasts in plan view shows a preferential direction, indicating weak currents and a longer time of exposition at the water/sediment interface; the occurrence of rare remains of deep infaunal suspension-feeding bivalves (Panopea (P.) cf. P. regularis) and crabs (Antarctidromia inflata) preserved in life position is indicative that this community was entombed in situ by sediments in suspension that brought the thanatocenosis of disarticulated valves. The results obtained in the present study reiterate the importance of taphonomic and paleoecological studies for the understanding of the depositional dynamics of the past and contribute a great number of data useful in the characterization of glacial and periglacial environments.

The research reported in this thesis focuses on Late Cretaceous and Cenozoic fossil brachiopods of Western Australia. Although the work is primarily taxonomic, it also includes biodiversity, distribution and some aspects of ecology of the brachiopods described.The most recent information on the anatomy, physiology and ecology of brachiopods is summarised at the beginning of the thesis.Identification of brachiopods is determined primarily on internal morphological features as brachiopods tend to be homomorphic, many species looking externally the same. The morphological features used in the identification of the brachiopods described within the thesis are defined.The fossil material studied has come from four sedimentary basins in Western Australia. The Carnarvon Basin contains Late Cretaceous and Cenozoic fossil material. The Perth Basin also has Late Cretaceous and late Cenozoic brachiopods The Bremer and Eucla Basin have Cenozoic deposits. The stratigraphy of the deposits containing the brachiopods is described.Until this study commenced, eight species had been described from Western Australia. This thesis describes fifty eight species including thirty new species, one new family and two new genera.In preparing descriptions of the new species it become evident that many of the species from the Southern Hemisphere were quite different to those found in the Northern Hemisphere. Their closest affiliation was with genera and species described from the Antarctic Peninsula. Four genera and one species from the Late Cretaceous deposits of Western Australia are common to the Late Cretaceous deposits of the Antarctic Peninsula. In the examination of the Tertiary material from the Carnarvon Basin, it also became clear that there was a strong correlation with Tertiary material from the Antarctic Peninsula. At least four genera are common to both deposits. Six brachiopod ++ / genera from the Middle Miocene deposits of the South Shetland Islands Antarctica are common to New Zealand. Nine genera, identified from the La Meseta Formation, Seymour Island, Antarctic Peninsula, are also common to New Zealand. These genera are also found in Australia. This evidence has led to the proposal that in the Late Cretaceous there was a common shelf environment from the Antarctic Peninsula to the north-west coast of Western Australia. In this area, which formed the high latitude southern circum-Indo-Atlantic faunal province, brachiopods evolved different genera and species than those in the northern hemisphere. Many then dispersed into northern areas of the Indian, Atlantic and finally Pacific Oceans.When the material from the Middle to Late Eocene of the Bremer and Eucla Basin was examined, five genera were found to be common to the Early Tertiary of the Carnarvon Basin. When comparing the species from the south-western basins and those from the south- east it was evident that similar species occur in the Middle to Late Eocene of the Bremer, Eucla, St Vincent and Murray Basins. There are some fifteen species in common. Many of these species then occur in the Late Oligocene south-eastern basins near Victoria and Tasmania as the gap between the Australia mainland and Tasmania began to open. One species that occurs in the Late Eocene of Western Australia is also described from the Late Oligocene of New Zealand.In considering the distribution of the Cenozoic brachiopods, genera first appear in the north-west of Western Australia and they then appear in chronological order in the south-western basins and south-eastern basins of South Australia, then the south-eastern basins of Victoria and Tasmania and then New Zealand. By the Late Eocene, there was a shallow marine connection between the Bight and the Tasman Sea. By the Late Oligocene this had widened and ++ / Australia was finally totally separated from Antarctica.The Proto-Leeuwin Current was responsible for the distribution of the brachiopods from the north-west of Western Australia to the southern coast. Possible mechanisms for the distribution of genera to New Zealand include rafting and an extended larval stage.It has been suggested that brachiopods in Australia are distributed according to the substrate on which they settle rather than any other factor. Using the information on the distribution of brachiopods in Western Australia throughout the Cenozoic this hypothesis is examined. It is suggested that avoidance of light in the photic zone and food availability with competition with bivalves are more important factors than substrate conditions.

The marsupial family Pseudocheiridae is currently known from seventeen species of six genera in Australia and New Guinea. These small to medium-sized arboreal animals are nocturnal and folivorous. Extinct pseudocheirids are recognised from several mid to late Cenozoic fossil localities across Australia and New Guinea. The single largest collection of pseudocheirid fossils has been recovered from the Oligo-Miocene freshwater carbonates of the Riversleigh World Heritage Area in northwest Queensland. This collection, which includes the first pseudocheirid cranial fossils, forms the basis of this investigation. Three new extinct pseudocheirid genera together containing four species are identified and described. Six new species of Paljara, Marlu and Pildra are also described from Riversleigh. Two of the new Marlu species are reported from South Australia??s Leaf Locality. From Riversleigh, Marlu kutjamarpensis is identified and additional material of Paljara tirarensae and P. nancyhawardae documented. New species attributed to Marlu and Pildra necessitate revision of those genera. Cranial material is identified for three of the new species. The rostrum of archaic pseudocheirids is shorter than in extant forms but cranial morphology is similar overall. Phylogenetic relationships of all extinct pseudocheirids are analysed. They include all new and previously described species, most of which have never been examined in a parsimony-based analysis. Two hypotheses of pseudocheirid evolution are presented: a paired lineage hypothesis and a single lineage hypothesis. Both hypotheses demonstrate that species of Paljara are not the most plesiomorphic pseudocheirids, Marlu praecursor does not cluster with other species of Marlu, the new genus Gawinga is most closely related to Paljara and there are no representatives of the extant genus Pseudochirops in any pre-Pliocene locality. All extant pseudocheirids cluster to form a crown clade sister to a stem lineage of Pseudokoala and Marlu species. Pseudocheirids are found in all Oligo-Miocene faunal zones of Riversleigh. Species of Paljara and Marlu are most frequently recovered from Faunal Zone B and C deposits respectively. Four pseudocheirid species biostratigraphically correlate the Kutjamarpu local fauna of the Leaf Locality with Faunal Zones B and C of Riversleigh, suggesting an early to middle Miocene age for both deposits. Modern pseudocheirids first evolved no later than the late Miocene from a descendant of the Marlu + Pseudokoala lineage when all other Oligo-Miocene pseudocheirids became extinct. At least three pseudocheirid lineages dispersed to New Guinea approximately five million years ago, but ecological barriers probably prevented subsequent migrations between the two landmasses.