ABSTRACT. Aspidella terranovica Billings, 1872 was ®rst described from the late Neoproterozoic Fermeuse Formation (St. John's Group) on the Avalon Peninsula of eastern Newfoundland, approximately 1 km stratigraphically above the famous Ediacaran biota at Mistaken Point, and several kilometres below the base of the Cambrian. Aspidella has been reinterpreted perhaps more than any other Precambrian taxon, and has variously been regarded as a fossil mollusc or medusoid', a gas escape structure, a concretion, or a mechanical suction mark. Our studies indicate that Aspidella includes a wide variety of preservational morphs varying from negative hyporeliefs with a raised rim and ridges radiating from a slit (Aspidella-type preservation), to¯at discs with a central boss and sharp outer ring (Spriggia preservation), to positive hyporeliefs with concentric ornamentation (Ediacaria preservation). Specimens occur in a continuum of sizes, with preservational styles dependent on the size of the specimen and the grain size of the host lithology; the elongation of specimens is tectonic. Aspidella is con®rmed as a body fossil from observations of complex radial and concentric ornamentation, mutually deformed borders in clusters of specimens, and occurrence on the same bedding planes as certain distinctive Ediacaran taxa. Aspidella is indistinguishable from, and has priority over, several of the most common genera of late Neoproterozoic discoidal body fossils worldwide. Similar fossils from Australia are interpreted as holdfasts of frond-like organisms. The density of specimens in the Aspidella beds suggests levels of benthic biomass in the Neoproterozoic that could rival those of modern marine communities. The serial growth forms, Palaeopascichnus, Intrites, Neonereites renarius and Yelovichnus, associated with Aspidella, are interpreted as body fossils of unknown af®nities rather than trace fossils. A new, trilobed, Ediacaran body fossil, Triforillonia costellae gen. et sp. nov., is described from the Aspidella beds of the Fermeuse Formation.T H E discovery and description of Aspidella terranovica Billings, 1872 in what is now known as the Fermeuse Formation of the St. John's Group, from the Avalon Zone of eastern Newfoundland (Text-®gs 1±2), came at a time when geologists were grappling with the relatively new disciplines of stratigraphy and systematic palaeontology. The earliest references to these discoidal impressions realized their utility in establishing stratigraphical relationships on the Avalon Peninsula (Murray 1868, 1873; Billings 1872). It was another matter to explain enormous numbers of fossils of apparently soft-bodied organisms in very old strata. The fact that the Aspidella-bearing formation clearly underlay the local trilobite-bearing`Primordial' strata, with marked unconformity, added to the concern of later commentators.Despite regular reviews of the status of Aspidella (see Hofmann, 1971 and references therein, plus subsequent references by Hsu È (1972), King (1980), Landing et al. (1988), Conway Morris (19...
The Burin Peninsula exhibits an exceptionally thick and essentially continuous succession of marine strata through the Precambrian–Cambrian transition. Fossils are abundant and include trace fossils, small shelly fossils, vendotaenid algae, soft-bodied megafossils, and microfossils. The Burin Peninsula is readily accessible and has long been considered a potential area for a Precambrian–Cambrian boundary stratotype.A continuous section through the upper part of member 1 and all of member 2 of the Chapel Island Formation is exposed at Fortune Head, and this section is herein proposed as a global stratotype for the Precambrian–Cambrian boundary. The boundary horizon is located 2.4 m above the base of member 2 of the Chapel Island Formation. This horizon marks the base of the basal Cambrian Phycodes pedum (ichnofossil) Zone and immediately overlies the top of the Late Precambrian Harlaniella podolica (ichnofossil) Zone. Shelly fossils (sabelliditids) first appear a few metres below the proposed boundary. Soft-bodied megafossils, carbonaceous impressions of vendotaenid algae, and organic-walled microfossils occur both below and above this boundary and enhance global correlation with this section.Fossils of the Rusophycus avalonensis (ichnofossil) Zone first appear midway through member 2 (approximately 135 m above the proposed boundary) and occur commonly throughout the upper part of the Chapel Island Formation and the overlying Random Formation. Calcareous small shelly fossils (?Circotheca sp.) appear near the top of member 2 (approximately 400 m above the proposed boundary), and a more diverse Aldanella attleborensis small shelly fossil assemblage characterizes the uppermost strata of member 3 and all of member 4 of the Chapel Island Formation (approximately 550–650 m above the proposed boundary). The lowest trilobites, representatives of the Callavia broeggeri Zone, first appear more than 1000 m above the proposed Precambrian–Cambrian boundary.
In the Napa Valley of California, vineyards of 'Cabernet Franc' (CF) clone 214, 'Cabernet Sauvignon' clone 337, and 'Zinfandel' clone 1A (Z1A) with grapevines exhibiting foliar symptoms of red blotches, marginal reddening, and red veins that were accompanied by reduced sugar accumulation in fruit at harvest were initially suspected to be infected with leafroll-associated viruses. However, reverse-transcription polymerase chain reaction (PCR) tests were negative for all known leafroll-associated viruses, with the exception of Grapevine leafroll-associated virus 2 in Z1A. Metagenomic analysis of cDNA libraries obtained from double-stranded RNA enriched nucleic acid (NA) preparations from bark scrapings of dormant canes on an Illumina platform revealed sequences having a distant relationship with members of the family Geminiviridae. Sequencing of products obtained by PCR assays using overlapping primers and rolling circle amplification (RCA) confirmed the presence of a single circular genome of 3,206 nucleotides which was nearly identical to the genome of a recently reported Grapevine cabernet franc-associated virus found in declining grapevines in New York. We propose to call this virus "Grapevine red blotch-associated virus" (GRBaV) to describe its association with grapevine red blotch disease. Primers specific to GRBaV amplified a product of expected size (557 bp) from NA preparations obtained from petioles of several diseased source vines. Chip bud inoculations successfully transmitted GRBaV to test plants of CF, as confirmed by PCR analysis. This is the first report of a DNA virus associated with red blotch disease of grapevines in California.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.