Deciphering The Preservation Of Fossil Insects: A Case Study From The Crato Member, Early Cretaceous Of Brazil

Exceptionally well-preserved three-dimensional insects with fine details and even labile tissues are ubiquitous in the Crato Member Konservat Lagerstätte (northeastern Brazil). Here we investigate the preservational pathways which yielded such specimens. We employed high resolution techniques (EDXRF, SR-SXS, SEM, EDS, micro Raman, and PIXE) to understand their fossilisation on mineralogical and geochemical grounds. Pseudomorphs of framboidal pyrite, the dominant fossil microfabric, display size variation when comparing cuticle with inner areas or soft tissues, which we interpret as the result of the balance between ion diffusion rates and nucleation rates of pyrite through the originally decaying carcasses. Furthermore, the mineral fabrics are associated with structures that can be the remains of extracellular polymeric substances (EPS). Geochemical data also point to a concentration of Fe, Zn, and Cu in the fossils in comparison to the embedding rock. Therefore, we consider that biofilms of sulphate reducing bacteria (SRB) had a central role in insect decay and mineralisation. Therefore, we shed light on exceptional preservation of fossils by pyritisation in a Cretaceous limestone lacustrine palaeoenvironment. © 2016 Osés et al.20161

Ecological interactions in Cloudina from the Ediacaran of Brazil : implications for the rise of animal biomineralization.

At the Ediacaran/Cambrian boundary, ecosystems witnessed an unparalleled biological innovation: the appearance of shelled animals. Here, we report new paleoecological and paleobiological data on Cloudina, which was one of the most abundant shelled animals at the end of the Ediacaran. We report the close association of Cloudina tubes with microbial mat textures as well as organic-rich material, syndepositional calcite and goethite cement between their flanges, thus reinforcing the awareness of metazoan/microorganism interactions at the end of the Ediacaran. The preservation of in situ tubes suggests a great plasticity of substrate utilization, with evidence of different life modes and avoidance behavior. Geochemical analysis revealed walls composed of two secondary laminae and organic sheets. Some walls presented boreholes that are here described as predation marks. Taken together, these data add further information regarding the structuring of shelled animal communities in marine ecosystems

Ediacaran metazoan fossil record from South America and its implications in the studies about origin and complexification of animal life

O Período Ediacarano marca o aparecimento dos primeiros organismos macroscópicos complexos no registro fóssil. Evidências atuais indicam que a biota de Ediacara é composta tanto por animais quanto por grupos de protistas gigantes extintos, além de algas e outros organismos sem afinidades comprovadas com representantes modernos. Fósseis dessa biota foram documentados em pelo menos 40 localidades no mundo. Na América do Sul, fósseis de metazoários ediacaranos são encontrados no Brasil, Paraguai, Uruguai e Argentina. Na maioria dessas localidades, são encontrados fósseis do último momento evolutivo da biota ediacarana, capazes de realizar esqueletogênese, tais como Cloudina e Corumbella, correlatos a assembleia Nama. Essa novidade evolutiva surgiu, provavelmente, em resposta a pressões de predação e mudanças químicas nos oceanos. Recentemente, foram encontrados fósseis de organismos de corpo mole, típicos de outra assembleia ediacarana (White Sea), em Santa Catarina (Brasil). Essa ocorrência é de grande relevância, uma vez que representa a única descoberta na América do Sul que apresenta organismos dessa assembleia. Este trabalho tem por objetivo compilar as ocorrências da biota de Ediacara na América do Sul, bem como discutir a importância da inserção e dos estudos dessas ocorrências no cenário mundial no escopo de uma das mais importantes questões da Paleobiologia: a origem e a evolução dos animais na Terra.The Ediacaran Period marks the first appearance of complex macroscopic organisms in the fossil record. Current evidence indicates that Ediacara biota is composed of animals, groups of extinct giant protists, algae and other organisms without proven affinities with modern groups. Fossils of this biota have been documented in at least 40 locations worldwide. In South America, ediacaran metazoan fossils are found in Brazil, Paraguay, Uruguay and Argentina. In most of these locations, are found fossils of the last moment of evolutionary ediacaran biota, capable of performing skeletogenesis, such as Cloudina and Corumbella, related to Nama assemblage. This evolutionary novelty arose probably in response to predation pressures and chemical changes in the oceans. Newly, fossils of soft-bodied organisms were found, typical of other ediacaran assembly (White Sea), in Santa Catarina (Brazil). This occurrence is of great importance since it represents the only discovery about its assemblage in South America. This work aims to compile the occurrences of the Ediacara biota in South America, as well as discussing the importance of inclusion and study these events on the world scene in the scope of one of the most important issues of Paleobiology: the origin and evolution animals on Earth

Paleobiologia e Evolução: o potencial do registro fossilífero brasileiro

A Paleobiologia é uma área que vem ganhando destaque mundial com seus estudos voltados para interpretações ecológicas, evolutivas e ambientais do registro fossilífero. Nesse contexto, o Brasil tem demonstrado grande potencial para o desenvolvimento de pesquisas que podem contribuir para compreensão da história e processos evolutivos dos organismos. Em seu vasto território, o país apresenta diversas localidades fossilíferas que contêm informações cruciais sobre a evolução e diversificação da vida na Terra. O Grupo Corumbá, em afloramentos da Formação Bocaina, apresenta evidências dos primeiros protistas eucariontes heterotróficos, além do posterior aparecimento dos primeiros metazoários capazes de realizar esqueletogênese, evidenciados na subsequente Formação Tamengo. O Membro Crato, no nordeste brasileiro, é reconhecido mundialmente pela preservação excepcional da paleoentomofauna e paleoflora do Cretáceo, e constitui uma das melhores possibilidades para pesquisas paleontológicas voltadas para a coevolução inseto-planta. Outro grande campo da Paleobiologia que vem sendo desenvolvida no país são os estudos sobre a paleomastofauna, principalmente dos abundantes fósseis pleistocênicos encontrados em diversas regiões do país, e que podem lançar novas informações quanto a extinção da megafauna e a convivência desta com as antigas populações humanas da época. Sendo assim, o Brasil possui uma ampla gama temporal em seu registro fóssil, e permite o desenvolvimento de pesquisas de ponta que ajudarão a responder importantes questões evolutivas sobre os organismos, inclusive aquelas envolvendo as megatrajetórias da vida

Environmental and diagenetic controls on the morphology and calcification of the Ediacaran metazoan Cloudina

Abstract Cloudina is a globally distributed Ediacaran metazoan, with a tubular, funnel-in-funnel form built of thin laminae (ca. 1–10 μm). To what degree local environmental controlled morphology, and whether early diagenesis controlled the degree of calcification of Cloudina, is debated. Here we test these hypotheses by considering assemblages from four, coeval localities from the Upper Omkyk Member, Nama Group, Namibia, from inner ramp to mid-ramp reef across the Zaris Subbasin. We show that sinuosity of the Cloudina tube is variable between sites, as is the relative thickness of the tube wall, suggesting these features were environmentally controlled. Walls are thickest in high-energy reef settings, and thinnest in the low-energy, inner ramp. While local diagenesis controls preservation, all diagenetic expressions are consistent with the presence of weakly calcified, organic-rich laminae, and lamina thicknesses are broadly constant. Finally, internal ‘cements’ within Cloudina are found in all sites, and pre-date skeletal breakage, transport, as well as syn-sedimentary botryoidal cement precipitation. Best preservation shows these to be formed by fine, pseudomorphed aragonitic acicular crystals. Sr concentrations and Mg/Ca show no statistically significant differences between internal Cloudina cements and botryoidal cements, but we infer all internal cements to have precipitated when Cloudina was still in-situ and added considerable mechanical strength, but may have formed post-mortem or in abandoned parts of the skeleton

Developing Freedom: Thomas Jefferson, the State, and Human Capability

Thomas Jefferson is often invoked as an advocate of limited government and a defender of individual rights. This article argues that rights were Jefferson’s starting place. Jefferson also believed that American citizens should have opportunities to develop the capabilities necessary to enjoy the full use of their rights. Rather than thinking about Jefferson as progovernment or antigovernment, this article concludes that we must understand the particular kind of government Jefferson desired, the ends he had in mind, and why and how those ends differed from his Federalist predecessors. A better understanding of Jefferson’s statecraft not only offers a new perspective on the relationship between government and rights in Jefferson’s thought but also how and why Jeffersonians in power used the state to promote individual freedom