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

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

Temporal and spatial analysis of the 2014-2015 Ebola virus outbreak in West Africa

West Africa is currently witnessing the most extensive Ebola virus (EBOV) outbreak so far recorded. Until now, there have been 27,013 reported cases and 11,134 deaths. The origin of the virus is thought to have been a zoonotic transmission from a bat to a two-year-old boy in December 2013 (ref. 2). From this index case the virus was spread by human-to-human contact throughout Guinea, Sierra Leone and Liberia. However, the origin of the particular virus in each country and time of transmission is not known and currently relies on epidemiological analysis, which may be unreliable owing to the difficulties of obtaining patient information. Here we trace the genetic evolution of EBOV in the current outbreak that has resulted in multiple lineages. Deep sequencing of 179 patient samples processed by the European Mobile Laboratory, the first diagnostics unit to be deployed to the epicentre of the outbreak in Guinea, reveals an epidemiological and evolutionary history of the epidemic from March 2014 to January 2015. Analysis of EBOV genome evolution has also benefited from a similar sequencing effort of patient samples from Sierra Leone. Our results confirm that the EBOV from Guinea moved into Sierra Leone, most likely in April or early May. The viruses of the Guinea/Sierra Leone lineage mixed around June/July 2014. Viral sequences covering August, September and October 2014 indicate that this lineage evolved independently within Guinea. These data can be used in conjunction with epidemiological information to test retrospectively the effectiveness of control measures, and provides an unprecedented window into the evolution of an ongoing viral haemorrhagic fever outbreak.status: publishe

Clay templates in Ediacaran vendotaeniaceans: Implications for the taphonomy of carbonaceous fossils

International audienceAbstract Although rare, sedimentary deposits containing exceptionally preserved fossils (i.e., Lagerstätten) have shaped our view on the history of life at particular intervals, such as those recording the Cambrian radiation of animals. Therefore, understanding the processes that lead to the fossilization of unmineralized tissues is crucial to better interpret these fossil assemblages. A key issue on the fossilization of exceptionally preserved fossils is linked to the role of clay minerals in the high-fidelity preservation of recalcitrant and soft tissues. Here, we show for the first time, an association of unusual fibrous clays with carbonaceous fossils (Vendotaenia) in the late Ediacaran Tamengo Formation (Mato Grosso do Sul State, western Brazil). The vendotaeniaceans occur in laminated mudstones/siltstones interpreted as being deposited in outer to distal mid-ramp depositionary settings. The fossils are characterized by ribbon-shaped compressions 0.56 mm in mean width. The fibrous clays are obliquely oriented with respect to the bedding plane, and follow the orientation of tectonically deformed structures. Our mineralogical, geochemical, and petrographic data demonstrate that these clays are mainly composed of chlorite-smectite mixed layered minerals, with >50% chlorite. Altogether, our results suggest that these fibrous minerals formed in the late-diagenetic zone to lower anchizone, reinforcing the previous idea that clay minerals associated with fossils are not necessarily related to the preservation of soft tissues. Instead, the initial preservative pathway in our fossils was probably restricted to organic matter conservation in reducing fine-grained sediments, similar to other deposits with carbonaceous fossils. This newly established mechanism, which involves the formation of clays on organic templates in the late-diagenetic zone, is likely a more widespread phenomenon than previously thought