Rebuilding Earth's first skeletal animals: the original morphology of (Ediacaran, Brazil).

The evolutionary onset of animal biomineralization in the late Ediacaran ( 555-538 Ma) is marked by the global appearance of enigmatic tubular fossils with unresolved phylogenetic relationships. Among these, from the Tamengo Formation (Corumbá Group, Brazil) has been variously interpreted as affiliated with cnidarians or bilaterians. Using synchrotron imaging and machine learning, we analysed new specimens of to reconstruct their original skeletal organization.

Deep water vetulicolians from the lower Cambrian of China.

Vetulicolians are an enigmatic phylum of extinct Cambrian marine invertebrates. They are particularly diverse in the Chengjiang Biota of China, but representatives have been recovered from other Fossil-Lagerstätten (Cambrian Stage 3-Drumian). These organisms are characterized by a bipartite body, which is split into an anterior section and a posterior segmented section connected by a narrow constriction.

Paleontology: Ediacaran ecology drove ocean ventilation.

Fluid dynamics modeling of an Ediacaran ecosystem illustrates an important positive feedback loop between early multicellular organisms and environmental water flow. Early communities thus helped to chemically shape new environments where oxygen-dependent organisms could thrive.

Annelids from the Cambrian (Wuliuan Stage, Miaolingian) Spence Shale Lagerstätte of northern Utah, USA.

The Spence Shale Member of the Langston Formation in northern Utah and southern Idaho preserves generally non-biomineralized fossil assemblages referred to as the Spence Shale Lagerstätte. The biota of this Lagerstätte is dominated by panarthropods, both biomineralized and soft-bodied examples, but also preserves diverse infaunal organisms, including species of scalidophorans, echinoderms, lobopodians, stalked filter feeders, and various problematic taxa. To date, however, only a single annelid fossil, originally assigned to sp.

The paleoredox context of early eukaryotic evolution: insights from the Tonian Mackenzie Mountains Supergroup, Canada.

Tonian (ca. 1000-720 Ma) marine environments are hypothesised to have experienced major redox changes coinciding with the evolution and diversification of multicellular eukaryotes. In particular, the earliest Tonian stratigraphic record features the colonisation of benthic habitats by multicellular macroscopic algae, which would have been powerful ecosystem engineers that contributed to the oxygenation of the oceans and the reorganisation of biogeochemical cycles.

A modern definition of Fossil-Lagerstätten.

Fossil-Lagerstätten are amongst the most important windows onto the paleobiology of ancient ecosystems. Inconsistencies surrounding what constitutes a Lagerstätte limits our ability to compare sites and thus their scientific potential. Here, we provide a modern and utilitarian classification scheme for Konservat-Lagerstätten, allowing for more consistent and improved scientific discourse.

Resolving taphonomic and preparation biases in silicified faunas through paired acid residues and X-ray microscopy.

Paired petrography and acid maceration has shown that preferential silicification of shelly faunas can bias recovery based on taxon and body size. Here, silicified fossils from the Upper Ordovician Edinburg Formation, Strasburg Junction, Virginia, USA, were analyzed using X-ray tomographic microscopy (μCT) in conjunction with recovered residues from acid maceration of the same materials to further examine sources of potential bias. Results reveal that very small (<~1 mm) fossils are poorly resolved in μCT when scanning at lower resolutions (~30 µm), underestimating abundance of taxa including ostracods and bryozoans.

from the Cambrian of China elucidates the dispersal and palaeogeographic distribution of early deuterostomes and the origin of the ambulacrarian larva.

The Cambrian Radiation represents one of the largest diversification events in Earth history. While the resulting taxonomic diversity is exceptional, relatively few of these novel species can be traced outside the boundaries of a single palaeocontinent. Many of those species with cosmopolitan distributions were likely active swimmers, presenting opportunity and means to conquer new areas, but this would not have been the case for sessile organisms.

Causes and consequences of end-Ediacaran extinction: An update.

Since the 1980s, the existence of one or more extinction events in the late Ediacaran has been the subject of debate. Discussion surrounding these events has intensified in the last decade, in concert with efforts to understand drivers of global change over the Ediacaran-Cambrian transition and the appearance of the more modern-looking Phanerozoic biosphere. In this paper we review the history of thought and work surrounding late Ediacaran extinctions, with a particular focus on the last 5 years of paleontological, geochemical, and geochronological research.

The role of iron in the formation of Ediacaran 'death masks'.

The Ediacara biota are an enigmatic group of Neoproterozoic soft-bodied fossils that mark the first major radiation of complex eukaryotic and macroscopic life. These fossils are thought to have been preserved via pyritic "death masks" mediated by seafloor microbial mats, though little about the chemical constraints of this preservational pathway is known, in particular surrounding the role of bioavailable iron in death mask formation and preservational fidelity. In this study, we perform decay experiments on both diploblastic and triploblastic animals under a range of simulated sedimentary iron concentrations, in order to characterize the role of iron in the preservation of Ediacaran organisms.

Paleontology: Paleogastronomy in the Ediacaran.

Preserved lipid biomarkers provide a unique window onto the biology of fossil organisms. A new study uses lipids to assess the gut contents of three fossils from the 'dawn of animals' in the Ediacaran, with implications for their feeding behaviors.

Preservation of early Tonian macroalgal fossils from the Dolores Creek Formation, Yukon.

The rise of eukaryotic macroalgae in the late Mesoproterozoic to early Neoproterozoic was a critical development in Earth's history that triggered dramatic changes in biogeochemical cycles and benthic habitats, ultimately resulting in ecosystems habitable to animals. However, evidence of the diversification and expansion of macroalgae is limited by a biased fossil record. Non-mineralizing organisms are rarely preserved, occurring only in exceptional environments that favor fossilization.

Global controls on phosphatization of fossils during the toarcian oceanic anoxic event.

Konservat-Lagerstätten-deposits with exceptionally preserved fossils-vary in abundance across geographic and stratigraphic space due to paleoenvironmental heterogeneity. While oceanic anoxic events (OAEs) may have promoted preservation of marine lagerstätten, the environmental controls on their taphonomy remain unclear. Here, we provide new data on the mineralization of fossils in three Lower Jurassic Lagerstätten-Strawberry Bank (UK), Ya Ha Tinda (Canada), and Posidonia Shale (Germany) -and test the hypothesis that they were preserved under similar conditions.

Ultrastructure of Ediacaran cloudinids suggests diverse taphonomic histories and affinities with non-biomineralized annelids.

Cloudinids have long been considered the earliest biomineralizing metazoans, but their affinities have remained contentious and undetermined. Based on well-preserved ultrastructures of two taxa, we here propose new interpretations regarding both their extent of original biomineralization and their phylogenetic affinity. One of these taxa is a new cloudinid from Mongolia, Zuunia chimidtsereni gen.

Discovery of bilaterian-type through-guts in cloudinomorphs from the terminal Ediacaran Period.

The fossil record of the terminal Ediacaran Period is typified by the iconic index fossil Cloudina and its relatives. These tube-dwellers are presumed to be primitive metazoans, but resolving their phylogenetic identity has remained a point of contention. The root of the problem is a lack of diagnostic features; that is, phylogenetic interpretations have largely centered on the only available source of information-their external tubes.

Melanosome diversity and convergence in the evolution of iridescent avian feathers-Implications for paleocolor reconstruction.

Some of the most varied colors in the natural world are created by iridescent nanostructures in bird feathers, formed by layers of melanin-containing melanosomes. The morphology of melanosomes in iridescent feathers is known to vary, but the extent of this diversity, and when it evolved, is unknown. We use scanning electron microscopy to quantify the diversity of melanosome morphology in iridescent feathers from 97 extant bird species, covering 11 orders.

Decoupling biogeochemical records, extinction, and environmental change during the Cambrian SPICE event.

Several positive carbon isotope excursions in Lower Paleozoic rocks, including the prominent Upper Cambrian Steptoean Positive Carbon Isotope Excursion (SPICE), are thought to reflect intermittent perturbations in the hydrosphere-biosphere system. Models explaining these secular changes are abundant, but the synchronicity and regional variation of the isotope signals are not well understood. Examination of cores across a paleodepth gradient in the Upper Cambrian central Missouri intrashelf basin (United States) reveals a time-transgressive, facies-dependent nature of the SPICE.

Proteins from the past.

Some fragments of ancient protein are less prone to degradation because they bind strongly to the surfaces of minerals.

A unifying model for Neoproterozoic-Palaeozoic exceptional fossil preservation through pyritization and carbonaceous compression.

Soft-tissue fossils capture exquisite biological detail and provide our clearest views onto the rise of animals across the Ediacaran-Cambrian transition. The processes contributing to fossilization of soft tissues, however, have long been a subject of debate. The Ediacaran Gaojiashan biota displays soft-tissue preservational styles ranging from pervasive pyritization to carbonaceous compression, and thus provides an excellent opportunity to dissect the relationships between these taphonomic pathways.

Validation of the MR simulation approach for evaluating the effects of immersion on visual analysis of volume data.

In our research agenda to study the effects of immersion (level of fidelity) on various tasks in virtual reality (VR) systems, we have found that the most generalizable findings come not from direct comparisons of different technologies, but from controlled simulations of those technologies. We call this the mixed reality (MR) simulation approach. However, the validity of MR simulation, especially when different simulator platforms are used, can be questioned.

Comment on "Fossilized nuclei and germination structures identify Ediacaran 'animal embryos' as encysting protists".

On the basis of putative nuclei and endospores, Huldtgren et al. (Reports, 23 December 2011, p. 1696) propose that embryo-like Doushantuo microfossils are nonmetazoan holozoans akin to mesomycetozoeans.

Effects of immersion on visual analysis of volume data.

Volume visualization has been widely used for decades for analyzing datasets ranging from 3D medical images to seismic data to paleontological data. Many have proposed using immersive virtual reality (VR) systems to view volume visualizations, and there is anecdotal evidence of the benefits of VR for this purpose. However, there has been very little empirical research exploring the effects of higher levels of immersion for volume visualization, and it is not known how various components of immersion influence the effectiveness of visualization in VR.