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No / Australopithecus anamensis is the stem species of all later hominins and exhibits the suite of characters traditionally associated with hominins, i.e., bipedal locomotion when on the ground, canine reduction, and thick-enameled teeth. The functional consequences of its thick enamel are, however, unclear. Without appropriate structural reinforcement, these thick-enameled teeth may be prone to failure. This article investigates the mechanical behavior of A. anamensis enamel and represents the first in a series that will attempt to determine the functional adaptations of hominin teeth. First, the microstructural arrangement of enamel prisms in A anamensis teeth was reconstructed using recently developed software and was compared with that of extant hominoids. Second, a finite-element model of a block of enamel containing one cycle of prism deviation was reconstructed for Homo, Pan, Gorilla, and A. anamensis and the behavior of these tissues under compressive stress was determined. Despite similarities in enamel microstructure between A. anamensis and the African great apes, the structural arrangement of prismatic enamel in A. anamensis appears to be more effective in load dissipation under these compressive loads. The findings may imply that this hominin species was well adapted to puncture crushing and are in some respects contrary to expectations based on macromorphology of teeth. Taking together, information obtained from both finite-element analyses and dental macroanatomy leads us to suggest that A. anamensis was probably adapted for habitually consuming a hard-tough diet. However, additional tests are needed to understand the functional adaptations of A. anamensis teeth fully.

The subgenus Rexmela, located primarily in Florida, is newly evolved, dating back 1.6 million years, first occurring in the Ayer's Landing Member of the Caloosahatchee Formation. This subgenus has highly variably shell morphology and has led to the erection of several species and subspecies. In order to provide a quantitative methodology with which to differentiate between populations, samples of Recent and fossil populations were collected and measured for a variety of parameters. The parameters measured included length, width, spire height, and several angles, and allowed for a discriminate analysis to be completed. The analysis supported the distinction of several of the populations as ecophenotypes. Paleoenvironments of the fossil populations were then recreated using analogues of Recent populations. / by Crystal Pletka. / Thesis (M.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

“Captorhinikos” chozaensis is a multiple-tooth-rowed captorhinid reptile from the Lower Permian Clear Fork Group, undivided formation. Upon re-examination of the materials associated with the species from both the Chicago Field Museum of Natural History, and the Smithsonian United States National Museum, I reaffirm their affinity and collective identity as a valid taxon. “Captorhinikos” chozaensis does not, however, belong with either of the two members of its genus, C. valensis or “C.” parvus, instead occupying its own branch on the phylogenetic tree of the Captorhinidae. This conclusion is based in strong results from a combined phylogenetic parsimony analysis combined with an analytical apomorphy analysis. I then conclude the current designation “Captorhinikos” chozaensis to be a nomen ambiguum.

Macroscopic “carbonaceous” fossils such as Grypania, Katnia, Chuaria, and Tawuia play a critical role in our understanding of biological evolution in the Precambrian and their environmental implications. Unfortunately, understanding of these fossils remains limited by their relative simplicity of form, mode of preservation, and broad taphonomic variability. As a result, debate continues as to even the fundamental taxonomic affinity of the organisms. Megascopic coiled forms (i.e. Grypania and Katnia), for instance, have been interpreted as trace fossils, multicellular algae, prokaryotic filaments, macroscopic bacteria, cyanobacteria, or a transitional form from macroscopic to megascopic bacterial life. Similarly, Chuaria and Tawuia have been interpreted as compressed prokaryotic colonies, algae or algal reproductive stages, and multicellular plant material. Accessibility of new material and increasingly sophisticated means of analysis warrant a new look at these ancient fossils. Understanding the biological affinity of Grypania, in particular, is critical because current opinion is split as to whether these megascopic structures are more likely represent either multicellular bacteria or multicellular algae. Confirmation of either a bacterial or algal affinity would strongly influence fundamental understanding of biospheric evolution, particularly in terms of ocean oxygenation and the availability of bioessential trace metals. Although estimates for the degree of oxygenation required for a Grypania-like multicellular algae are only about 10 % present atmospheric levels (PAL), this estimate is still substantially higher than estimates based on geochemical data suggesting that oxygen levels may not have reached 10% PAL until the latter Neoproterozoic. It has been hypothesized that protracted oxygen of the Proterozoic biosphere may have played a critical role in the availability of redox-sensitive nutrients necessary for bacterial nitrogen fixation and the limiting of eukaryotic evolution. Within this context, our understanding of the taxonomic affinity of Grypania may profoundly affect our understanding of Earth’s biospheric evolution. This thesis provides morphological and geochemical analyses of Grypania spiralis from more than 100 newly collected specimens from the Belt Supergroup for comparison to previously collected specimens from all other known Grypania-bearing localities. Data is used to explore questions regarding the morphology, structural complexity, mode of preservation, and chemistry of fossil material, and to hypothesize on the taxonomic affinity of Grypania spiralis and its implications for biospheric evolution.

Thesis (Ph.D.)--University of Adelaide, Dept. of Geographical and Environmental Studies, 2001. / Includes bibliographical references (p. 301-319).

Esta tese aborda a geobiologia do único Atol do Oceano Atlântico Sul. Diferentes classificações foram realizadas para o complexo recifal de Rocas ao longo dos séculos XIX e XX, as quais são avaliadas historicamente. Análises biogeomorfológicas e de mapeamento das unidades recifais foram realizadas no Atol das Rocas para a compreensão da dinâmica sedimentar e do relevo deste recife oceânico. Os diferentes compartimentos recifais são afetados por processos biogeomorfológicos como controle de processos erosivos, bioproteção, bioerosão recifal, bioturbação, cimentação de areia carbonática biogênica, produção de sedimentos biodetríticos e bioconstrução (principalmente de algas calcáreas, corais, vermetídeos e foraminíferos). Organismos diversos incluindo aves, peixes, tartarugas, corais, zoantídeos, algas, moluscos, poliquetas, sipunculídeos, foraminíferos e microorganismos agem nos diferentes grupos de processos biogeomorfológicos gerando as características únicas do Atol. O recife oceânico se desenvolveu provavelmente nos últimos 7000 anos do Período Neógeno. A paleohidrodinâmica da corrente oceânica, variações no gradiente de energia no lado a barlavento e sotavento e, sobretudo, as oscilações eustáticas holocênicas foram preponderantes na evolução recifal. Em níveis de mar alto uma grande laguna composta por comunidades bentônicas se formou com grande diversidade biológica. Eventos regressivos e de erosão por ação de ondas e correntes levou as feições observadas atualmente, tais como o ambiente lagunar raso (<6m profundidade), de um amplo depósito arenoso e das ilhas à sotavento. A dinâmica temporal e espacial de sete comunidades principais de ambientes submersos, intertidais e emersos é demonstrada pela primeira vez. / This thesis approaches the geobiology of the only Atoll in the South Atlantic Ocean. Different classifications were made for Rocas Reef Complex along the nineteenth and twentieth century, which are evaluated historically. Biogeomorphological analysis and mapping of the reef units were done on the Rocas Atoll for the comprehension of the sedimentary dynamic and of the relief of this oceanic reef. The different reef compartments are affected by biogeomorphological processes such as erosive process control, bioprotection, bioerosion, bioturbation, cementing of the biogenic carbonate sand, production of biodetritic sediments and bioconstruction (especially of calcareous algae, vermetids, corals and foraminifers). Different organisms including birds, fishes, turtles, corals, zoanthids, algae, mollusks, polychaets, sipunculids, foraminifers and microorganisms act in the different groups of biogeomorphological processes generating the unique characteristics of the Atoll. The oceanic reef developed over the past 7000 years in the Neogene Period. The paleohydrodynamic of the oceanic current, variations of the gradient of energy on the leeward/windward side and, above all, the eustatic holocenic oscillations were predominant in the reef evolution. In high sea levels a lagoon composed by bentonic communities formed with great biological diversity. The regression and erosion by waves and currents led to the formation of shallow lagoon environment, extensive sandy deposit and the Islands in leeward side. The temporal and spatial dynamic of seven main communities of underwater, intertidal and emerged environments is shown for the first time.

Dicinodontes (Therapsida: Anomodontia) compreendem os principais herbívoros do intervalo Permiano Médio-Triássico Superior. Algumas de suas características morfofuncionais cranianas têm se mostrado boas adaptações à herbivoria e ao eficiente processamento oral de materiais vegetais, bem como à termorregulação. Dentre estas, a aquisição da propalinia (movimentação ânteroposterior da mandíbula) e a substituição de um aparelho mastigatório com dentes por uma ranfoteca cobrindo boa parte da extremidade anterior do crânio são os mais característicos. Na anatomia corpórea como um todo, a aquisição de uma postura mais ereta (upright), o aumento do tamanho corpóreo e a presença de turbinais são indicativos de que o grupo evoluiu para um padrão de vida mais ativo e, consequentemente, com um maior gasto energético. Neste trabalho, é apresentada uma revisão bibliográfica sobre tais adaptações e uma discussão sobre sua origem e evolução no clado Anomodontia, focando a espécie Jachaleria candelariensis Araújo & Gonzaga, 1980 do Triássico Superior do Rio Grande do Sul, Brasil. / Dicynodonts (Therapsida: Anomodontia) comprise the main herbivores of the Middle Permian - Upper Triassic interval. Some of their morphological and functional cranial characteristics revealed to be adaptations to herbivory and efficient oral processing of plant materials, as well thermoregulation. Among these, the acquisition of propaliny (anteroposterior movements of mandible) and the replacement of the teeth by a ramphoteca covering most of the snout are the most characteristic adaptations. Regarding to their overall shape, the acquisition of a more erect (upright) gait, the increase in body size and the presence of turbinals indicate that this group evolved toward a more active lifestyle and, consequently with a most energetic cost. In this dissertation, is presented a bibliographic revision about such adaptations and a discussion about its origin and evolution within Anomodontia, focusing the Upper Triassic Jachaleria candelariensis Araújo & Gonzaga, 1980, from Rio Grande do Sul State, southern Brazil. / Los dicinodontes (Therapsida: Anomodontia) fueron los principales herbívoros durante el intervalo Pérmico Medio - Triásico Tardío. Presentaban varios caracteres morfofuncionales que reflejan adaptaciones al hábito herbívoro, así como a la termoregulación. Entre las más comunes están la adquisición de la propalinía (movimentación antero-posterior de la mandíbula) y la sustitución de un aparato masticatorio con dientes post-caninos por uno con forma de pico cubierto por una ranfoteca. Otros caracteres como la adquisición de una posición mas erecta (upright), aumento de la talla corporal y la presencia de turbinales son indicativos de que el clado evolucionó hacia un patrón de vida mas activo, y consecuentemente, de un mayor consumo de energía. En este trabajo se realizó una revisión bibliográfica de dichas adaptaciones y se discutió sobre su origen y evolución dentro del grupo Anomodontia, con un enfoque en el taxon Jachaleria candelariensis Araújo & Gonzaga, 1980 del Triásico Tardío de Rio Grande do Sul, Brasil.

Esta tese aborda a geobiologia do único Atol do Oceano Atlântico Sul. Diferentes classificações foram realizadas para o complexo recifal de Rocas ao longo dos séculos XIX e XX, as quais são avaliadas historicamente. Análises biogeomorfológicas e de mapeamento das unidades recifais foram realizadas no Atol das Rocas para a compreensão da dinâmica sedimentar e do relevo deste recife oceânico. Os diferentes compartimentos recifais são afetados por processos biogeomorfológicos como controle de processos erosivos, bioproteção, bioerosão recifal, bioturbação, cimentação de areia carbonática biogênica, produção de sedimentos biodetríticos e bioconstrução (principalmente de algas calcáreas, corais, vermetídeos e foraminíferos). Organismos diversos incluindo aves, peixes, tartarugas, corais, zoantídeos, algas, moluscos, poliquetas, sipunculídeos, foraminíferos e microorganismos agem nos diferentes grupos de processos biogeomorfológicos gerando as características únicas do Atol. O recife oceânico se desenvolveu provavelmente nos últimos 7000 anos do Período Neógeno. A paleohidrodinâmica da corrente oceânica, variações no gradiente de energia no lado a barlavento e sotavento e, sobretudo, as oscilações eustáticas holocênicas foram preponderantes na evolução recifal. Em níveis de mar alto uma grande laguna composta por comunidades bentônicas se formou com grande diversidade biológica. Eventos regressivos e de erosão por ação de ondas e correntes levou as feições observadas atualmente, tais como o ambiente lagunar raso (<6m profundidade), de um amplo depósito arenoso e das ilhas à sotavento. A dinâmica temporal e espacial de sete comunidades principais de ambientes submersos, intertidais e emersos é demonstrada pela primeira vez. / This thesis approaches the geobiology of the only Atoll in the South Atlantic Ocean. Different classifications were made for Rocas Reef Complex along the nineteenth and twentieth century, which are evaluated historically. Biogeomorphological analysis and mapping of the reef units were done on the Rocas Atoll for the comprehension of the sedimentary dynamic and of the relief of this oceanic reef. The different reef compartments are affected by biogeomorphological processes such as erosive process control, bioprotection, bioerosion, bioturbation, cementing of the biogenic carbonate sand, production of biodetritic sediments and bioconstruction (especially of calcareous algae, vermetids, corals and foraminifers). Different organisms including birds, fishes, turtles, corals, zoanthids, algae, mollusks, polychaets, sipunculids, foraminifers and microorganisms act in the different groups of biogeomorphological processes generating the unique characteristics of the Atoll. The oceanic reef developed over the past 7000 years in the Neogene Period. The paleohydrodynamic of the oceanic current, variations of the gradient of energy on the leeward/windward side and, above all, the eustatic holocenic oscillations were predominant in the reef evolution. In high sea levels a lagoon composed by bentonic communities formed with great biological diversity. The regression and erosion by waves and currents led to the formation of shallow lagoon environment, extensive sandy deposit and the Islands in leeward side. The temporal and spatial dynamic of seven main communities of underwater, intertidal and emerged environments is shown for the first time.

Dicinodontes (Therapsida: Anomodontia) compreendem os principais herbívoros do intervalo Permiano Médio-Triássico Superior. Algumas de suas características morfofuncionais cranianas têm se mostrado boas adaptações à herbivoria e ao eficiente processamento oral de materiais vegetais, bem como à termorregulação. Dentre estas, a aquisição da propalinia (movimentação ânteroposterior da mandíbula) e a substituição de um aparelho mastigatório com dentes por uma ranfoteca cobrindo boa parte da extremidade anterior do crânio são os mais característicos. Na anatomia corpórea como um todo, a aquisição de uma postura mais ereta (upright), o aumento do tamanho corpóreo e a presença de turbinais são indicativos de que o grupo evoluiu para um padrão de vida mais ativo e, consequentemente, com um maior gasto energético. Neste trabalho, é apresentada uma revisão bibliográfica sobre tais adaptações e uma discussão sobre sua origem e evolução no clado Anomodontia, focando a espécie Jachaleria candelariensis Araújo & Gonzaga, 1980 do Triássico Superior do Rio Grande do Sul, Brasil. / Dicynodonts (Therapsida: Anomodontia) comprise the main herbivores of the Middle Permian - Upper Triassic interval. Some of their morphological and functional cranial characteristics revealed to be adaptations to herbivory and efficient oral processing of plant materials, as well thermoregulation. Among these, the acquisition of propaliny (anteroposterior movements of mandible) and the replacement of the teeth by a ramphoteca covering most of the snout are the most characteristic adaptations. Regarding to their overall shape, the acquisition of a more erect (upright) gait, the increase in body size and the presence of turbinals indicate that this group evolved toward a more active lifestyle and, consequently with a most energetic cost. In this dissertation, is presented a bibliographic revision about such adaptations and a discussion about its origin and evolution within Anomodontia, focusing the Upper Triassic Jachaleria candelariensis Araújo & Gonzaga, 1980, from Rio Grande do Sul State, southern Brazil. / Los dicinodontes (Therapsida: Anomodontia) fueron los principales herbívoros durante el intervalo Pérmico Medio - Triásico Tardío. Presentaban varios caracteres morfofuncionales que reflejan adaptaciones al hábito herbívoro, así como a la termoregulación. Entre las más comunes están la adquisición de la propalinía (movimentación antero-posterior de la mandíbula) y la sustitución de un aparato masticatorio con dientes post-caninos por uno con forma de pico cubierto por una ranfoteca. Otros caracteres como la adquisición de una posición mas erecta (upright), aumento de la talla corporal y la presencia de turbinales son indicativos de que el clado evolucionó hacia un patrón de vida mas activo, y consecuentemente, de un mayor consumo de energía. En este trabajo se realizó una revisión bibliográfica de dichas adaptaciones y se discutió sobre su origen y evolución dentro del grupo Anomodontia, con un enfoque en el taxon Jachaleria candelariensis Araújo & Gonzaga, 1980 del Triásico Tardío de Rio Grande do Sul, Brasil.