<i>Velatasphaera hudsonii</i>gen. et sp. nov., an Ordovician acritarch from Hudson Strait, North West territories, Canada

Miller, Merrell A.; Williams, Graham L.

doi:10.1080/01916122.1988.9989339

Cited by 13 publications

(3 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the latter case, the apparently hollow space must originally have contained tissue, and the terms endo-, meso-and ectophragm, implying a certain analogy with the biological vocabulary, are sometimes used. The presence of tubiform processes separating the external from the internal layer is exceptionally recorded (Miller & Williams, 1988). The structure of the vesicle wall was first known from observations at a magnification of about x 1000 using the optical transmitted light microscope.…”

Section: How To Find Isolate and Recognize An Acritarch ( I ) Samplingmentioning

confidence: 99%

Acritarchsa Review

Martin

1993

Biological Reviews

100

View full text Add to dashboard Cite

Summary 1. Acritarchs are a polyphyletic group of unicellular organisms, essentially marine and fossil, with a very resistant organic membrane; the majority probably represent the cysts of microscopic, extinct eukaryote algae. This review gives a general account for the non‐specialist of their characteristics and affinities, but focuses, using selected examples, on their role as biostratigraphic tools for the specialist. 2. Invisible to the naked eye, up to several tens of thousands of acritarchs per gram of rock may be extracted and concentrated from a wide variety of sediments, especially argillaceous or even calcareous, but preferably fine‐grained, unweathered and only slightly recrystallized or metamorphosed. 3. Always hollow and without unequivocal intracellular structures, acritarchs are extremely variable inoverall size, from a few to several hundred μm, with numerous divergent morphological modifications from a basic spherical form; the type and development of ornamentation; the number of cellular walls; and the method of opening, attributed to excystment. Acritarchs are classified according to criteria that are relatively simple compared with the modern demands of phycologists. For convenience they are treated under the International Code of Botanical Nomenclature, recognizing the existence of form genera of uncertain position. The lack of a comprehensive taxonomic framework is not surprising, given the number and variety of unclassifiable microorganisms resistant to HF that may be included in the acritarchs. 4. The sporopollenin‐like wall of acritarchs, like the sporopollenin of modern plants, is chemically very inert except to oxidation, carbonization and bacterial or fungal activity. Of poorly‐known composition but very probably including highly polymerized polyterpenes, it may form an abundant component of Palaeozoic kerogen, a potential source of hydrocarbons. The codification of colour changes and preservation in selected acritarchs may enable the optical evaluation of palaeotemperatures lower than about 120–150 °C and of the degree of maturity of possible oils. 5. The first known acritarchs sensu stricto, although discovered in 1862, were designated as such in 1963, after having been given a variety of names reflecting mainly assessments of their biological affinities. In spite of some attempts to abandon it, the name acritarch is still the most correct as it is the least ambiguous for designating the great majority of examples. 6. The reclassifying of acritarchs among microorganisms of known systematic position remains speculative or tentative. It is possible that many acritarchs represent cysts of extinct dinoflagellates, without archaeopyle or indication of a stable tabulation. Laboratory culture of Pterosperma has shown that Cymatiosphaera and Pterospermella have to be considered not as acritarchs but as phycoma of prasinophytes. The ultrastructure of the wall in Tasmanites is similar to that of Pachysphaera, another recent prasinophyte. Comparisons with euglenoids or spore‐like bodies of the ...

show abstract

Section: How To Find Isolate and Recognize An Acritarch ( I ) Samplingmentioning

confidence: 99%

Acritarchsa Review

Martin

1993

Biological Reviews

100

View full text Add to dashboard Cite

show abstract

“…These form the bedrock of the innermost areas of the Baffin shelf and presumably underlie Phanerozoic rocks seaward. Middle and Upper Ordovician rocks have been identified on Akpatok Island in Ungava Bay (Workum et al, 1976), while Upper Ordovician rocks are known in Hudson Strait and Ungava Bay (Miller and Williams, 1988). Middle and Upper Ordovician rocks have been identified on Akpatok Island in Ungava Bay (Workum et al, 1976), while Upper Ordovician rocks are known in Hudson Strait and Ungava Bay (Miller and Williams, 1988).…”

Section: Regional Geologymentioning

confidence: 99%

New insights into the stratigraphy and petroleum potential of the Baffin shelf's Cretaceous rocks

MacLean¹,

Williams²,

Zhang³

2014

Bulletin of Canadian Petroleum Geology

View full text Add to dashboard Cite

“…This material, and the manner of its separation from the vesicle surface, superficially resembles the torn outer wall of a Velatasphaera hudsonii specimen figured by Miller and Williams [65] (Plate 2). However, in our specimen the torn material, where it is not ripped up, adheres to the surface of our specimen, including the spines, as is seen in Figure 11A,B, whereas in V. hudsonii the torn material represents a rugose sheet propped up on the tips of the spines [65] (Plates 2.2, 2.3, 2.4) At higher magnification, this thin surface layer in our specimen ( Figure 11A-C) is seen to contain numerous shallow, circular and ovate pits, resembling collapsed air bubbles ( Figure 11B). This is unlike the torn sheet observed in V. hudsonii, which is devoid of such pits.…”

Section: Surface Coveringmentioning

confidence: 99%

A Mineralized Alga and Acritarch Dominated Microbiota from the Tully Formation (Givetian) of Pennsylvania, USA

Chamberlain

Brown

2016

Geosciences

View full text Add to dashboard Cite

Sphaeromorphic algal cysts, most probably of the prasinophyte Tasmanites, and acanthomorphic acritarch vesicles, most probably Solisphaeridium, occur in a single 20 cm thick bed of micritic limestone in the lower part of the Middle Devonian (Givetian) Tully Formation near Lock Haven, Pennsylvania. Specimens are composed of authigenic calcite and pyrite crystals about 5-10 µm in length. Some specimens are completely calcitic; some contain both pyrite and calcite; and many are composed totally of pyrite. The microfossils are about 80 to 150 µm in diameter. Many show signs of originally containing a flexible wall composed of at least two layers. Some appear to have been enclosed in a mucilaginous sheath or membrane when alive. The acanthomorphic forms have spines that are up to 20 µm in length, expand toward the base, and are circular in cross-section. The microflora occurs with microscopic molluscs, dacryoconarids, the enigmatic Jinonicella, and the oldest zooecia of ctenostome bryozoans known from North America. The microalgal horizon lacks macrofossils although small burrows are present. Microalgae and acritarchs have been preserved via a complex preservational process involving rapid, bacterially-mediated post-mortem mineralization of dead cells. The microfossil horizon, and possibly much of the Tully Formation at Lock Haven with similar lithology, formed in a relatively deep, off-shore basin with reduced oxygen availability in the substrate.

show abstract

Velatasphaera hudsoniigen. et sp. nov., an Ordovician acritarch from Hudson Strait, North West territories, Canada

Cited by 13 publications

References 10 publications

Acritarchsa Review

Acritarchsa Review

New insights into the stratigraphy and petroleum potential of the Baffin shelf's Cretaceous rocks

A Mineralized Alga and Acritarch Dominated Microbiota from the Tully Formation (Givetian) of Pennsylvania, USA

Contact Info

Product

Resources

About