Early Archean (approximately 3.4 Ga) prokaryotic filaments from cherts of the apex basalt, Western Australia: The oldest cellularly preserved microfossils now known

In comparison with that known from later geologic time, the Archean fossil record is miniscule: although literally hundreds of Proterozoic formations, containing more that 2800 occurrences of bona fide microfossils are now known, fewer than 30 units containing some 43 categories of putative microfossils (the vast majority of which are of questionable authenticity) have been reported from the Archean. Among the oldest known fossils are Early Archean filaments reported from cherts of the Towers Formation and the Apex Basalt of the 3.3-3.6 Ga-old Warrawoona Group of Western Australia. The paleobiologic significance of the Towers Formation microstructures is open to question: thin aggregated filaments are properly regarded as dubiomicrofossils (perhaps biogenic, but perhaps not); therefore, they cannot be regarded as firm evidence of Archean life. Although authentic, filamentous microfossiles were reported from a second Towers Formation locality, because the precise layer containing the fossiliferous cherts was not relocated, this discovery can neither be reconfirmed by the original collector nor confirmed independently by other investigators. Discovery of microfossils in bedded cherts of the Apex Basalt, the stratigraphic unit immediately overlying the Towers Formation, obviates the difficulties stored above. The cellularly preserved filaments of the Apex Basalt meet all of the criteria required of a bona fide Archean microfossils. Recent studies indicate that the Apex assemblage includes at least six morphotypes of uniseriate filaments, composed of barrel-shaped, discoidal, or quadrate cells and exhibiting rounded or conical terminal cells and medial bifurcated and paired half-cells that reflect the occurrence of prokaryotic binary cell division. Interestingly, the majority of these morphotypes are morphologically more similar to extant cyanobacteria than to modern filamentous bacteria. Prokaryotes seem clearly to have been hypobradytelic, and the evidence suggests (but does not prove) that physiologically advanced oxygen-producing photosynthesizers may have been represented in the Early Archean biota

Micropaleontological studies of lunar samples. A search for biogenic structures in the Apollo 12 lunar samples

Biogeochemical and microstructural analyses on lunar rock and dust samples for biological compound

A Paleontological Study of the Gunflint Microfossil Assemblage

Precambrian microfossils discovered in nonferruginous charts of the lower algal members of the Gunflint formation of southern Ontario are of great interest in the evolutionary scheme of primitive life. The environment of deposition of the deposit, and the indigenous and biogenic nature of the microfossil assemblage are considered. A discussion of the small but diversified assemblage, including twelve micro-forms, seven of which have not previously been reported, is presented

A Paleontological Study of the Gunflint Microfossil Assemblage

Precambrian microfossils discovered in nonferruginous charts of the lower algal members of the Gunflint formation of southern Ontario are of great interest in the evolutionary scheme of primitive life. The environment of deposition of the deposit, and the indigenous and biogenic nature of the microfossil assemblage are considered. A discussion of the small but diversified assemblage, including twelve micro-forms, seven of which have not previously been reported, is presented

Controls on development and diversity of Early Archean stromatolites

The ≈3,450-million-year-old Strelley Pool Formation in Western Australia contains a reef-like assembly of laminated sedimentary accretion structures (stromatolites) that have macroscale characteristics suggestive of biological influence. However, direct microscale evidence of biology—namely, organic microbial remains or biosedimentary fabrics—has to date eluded discovery in the extensively-recrystallized rocks. Recently-identified outcrops with relatively good textural preservation record microscale evidence of primary sedimentary processes, including some that indicate probable microbial mat formation. Furthermore, we find relict fabrics and organic layers that covary with stromatolite morphology, linking morphologic diversity to changes in sedimentation, seafloor mineral precipitation, and inferred microbial mat development. Thus, the most direct and compelling signatures of life in the Strelley Pool Formation are those observed at the microscopic scale. By examining spatiotemporal changes in microscale characteristics it is possible not only to recognize the presence of probable microbial mats during stromatolite development, but also to infer aspects of the biological inputs to stromatolite morphogenesis. The persistence of an inferred biological signal through changing environmental circumstances and stromatolite types indicates that benthic microbial populations adapted to shifting environmental conditions in early oceans

Big Data and Analysis of Data Transfers for International Research Networks Using NetSage

Modern science is increasingly data-driven and collaborative in nature. Many scientific disciplines, including genomics, high-energy physics, astronomy, and atmospheric science, produce petabytes of data that must be shared with collaborators all over the world. The National Science Foundation-supported International Research Network Connection (IRNC) links have been essential to enabling this collaboration, but as data sharing has increased, so has the amount of information being collected to understand network performance. New capabilities to measure and analyze the performance of international wide-area networks are essential to ensure end-users are able to take full advantage of such infrastructure for their big data applications. NetSage is a project to develop a unified, open, privacy-aware network measurement, and visualization service to address the needs of monitoring today's high-speed international research networks. NetSage collects data on both backbone links and exchange points, which can be as much as 1Tb per month. This puts a significant strain on hardware, not only in terms storage needs to hold multi-year historical data, but also in terms of processor and memory needs to analyze the data to understand network behaviors. This paper addresses the basic NetSage architecture, its current data collection and archiving approach, and details the constraints of dealing with this big data problem of handling vast amounts of monitoring data, while providing useful, extensible visualization to end users

The paleobiological record of photosynthesis

Fossil evidence of photosynthesis, documented in Precambrian sediments by microbially laminated stromatolites, cyanobacterial microscopic fossils, and carbon isotopic data consistent with the presence of Rubisco-mediated CO2-fixation, extends from the present to ~3,500 million years ago. Such data, however, do not resolve time of origin of O2-producing photoautotrophy from its anoxygenic, bacterial, evolutionary precursor. Though it is well established that Earth’s ecosystem has been based on autotrophy since its very early stages, the time of origin of oxygenic photosynthesis, more than 2,450 million years ago, has yet to be established

Abstractions, accounts and grid usability

The vision of the Grid is one of seamless, virtual and constantly changing resources where users need not concern themselves about details, such as exactly where an application is running or where their data is being stored. However, seamless and virtual often imply a lack of control that users may be wary of, or even opposed to. Drawing upon our studies of HCI and of collaborative work, this paper examines whether the Grid development community should be taking this vision literally and argues for the need for accountability of systems ‘in interaction’. We give examples of an alternative approach that seeks to provide ways in which administrators, technical support and user communities can make sense of the behaviour of the complex socio-technical ensembles that are the reality of Grids

Ectoproct and entoproct type material: Reexamination of species from New England and Bermuda named by A. E. Verrill, J. W. Dawson and E. Desor

A. E. Verrill, J. W. Dawson, and E. Desor named 23 species of North American east coast ectoprocts and entoprocts prior to 1902. Chiefly from lack of illustration, the majority of these have been misunderstood in the literature. We have found material leading to a better understanding of 15 of these species in collections of the Peabody Museum of Natural History, Yale University, the U.S. National Museum, and the American Museum of Natural History. The following ectoproct species are described (original names): Amathia goodei Verrill, Bugula cucullata Verrill, Bugula decorata Verrill, Bugula flexilis Verrill, Bugula (Caulibugula) armata Verrill, Bugulella fragilis Verrill, Cellularia turrita Desor, Discopora nitida Verrill, Escharina porosa Verrill, Gemellaria willisii Dawson, Hippoporina verrilli Maturo and Schopf, Hippothoa expansa Dawson, Lepralia americana Verrill, Lepralia plana Dawson, Porellina stellata Verrill. One entoproct, Barentsia timida Verrill, is described. The coefficient of variation was determined for standard dimensional features. Data collected support Cheetham\u27s statistical verification that the most useful dimensional features for taxonomic purposes are ovicell length and width, zooid length, and primary orifice length and width. Length of adventitous avicularia and zooid width are the most variable of the traits measured, particularly in encrusting forms which also have extensive secondary calcification

Ritmo e modo da evolução microbiana pré-cambriana

Over the past quarter-century, detailed genus - and species-level similarities in cellular morphology between described taxa of Precambrian microfossils have been noted and regarded as biologically and taxonomically significant by numerous workers worldwide. Such similarities are particularly well-documented for members of the Oscillatoriaceae and Chroococcaceae, the two most abundant and widespread Precambrian cyanobacterial families.For species of two additional families, the Entophysalidaceae and Pleurocapsaceae, species-level morphologic similarities are supported by in-depth fossil-modern comparisons of environment, taphonomy, development, and behavior. Morphologically and probably physiologically as well, such cyanobacterial living fossils have exhibited an extraordinarily slow (hypobradytelic) rate of evolutionary change, evidently a result of the broad ecologic tolerance characteristic of many members of the group (and a striking example of Simpson's "rule of the survival of the relatively unspecialized"). In both tempo and mode of evolution, much of the Precambrian history of life - that dominated by microscopic cyanobacteria and related prokaryotes - appears to have differed markedly from the more recent Phanerozoic evolution of megascopic, horotelic, adaptationally specialized eukaryotes.No decorrer do último quarto de século, semelhanças detalhadas, em níveis de gênero e espécie, entre microfósseis pré-cambrianos e cianobactérias atuais, têm sido repetidamente anotadas e consideradas significativas biológica e taxonómicamente por grande número de pesquisadores espalhados pelo mundo. Estas semelhanças são particularmente bem-documentadas em membros das Oscillatoriaceae e Chroococcaceae, as duas famílias cianobacterianas pré-cambrianas mais amplamente distribuídas e abundantes. Em espécies de duas outras famílias, as Entophysalidaceae e Pleurocapsaceae, semelhanças morfológicas, em nível de espécie, entre fósseis e formas modernas apoiam-se em comparações profundas, abrangendo ambiente, tafonomia, desenvolvimento e comportamento. Morfológica e, provavelmente, fisiológicamente, tais fósseis vivos cianobacterianos evidenciam uma taxa de mudança evolutiva extraordinariamente lenta (hipobraditélica), evidentemente em conseqüência da larga tolerância ecológica característica de muitos membros do grupo, constituindo, assim, notável exemplo da "regra de sobrevivência dos relativamente pouco especializados", elaborada por Simpson. Tanto no ritmo quanto no modo de evolução, muito da história pré-cambriana da vida - aquela parte que foi dominada pelas microscópicas cianobactérias e outros procariotos - parece ter sido marcadamente diferente da evolução mais recente, fanerozóica, dos organismos eucarióticos, megascópicos, especializados e horotélicos