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Circulodinium araneosum
From Fensome et al., 2019:
Circulodinium araneosum (Brideaux, 1977, p.22–23, pl.9, figs.1–3) Fauconnier in Fauconnier and Masure, 2004, p.115.
Holotype: Brideaux, 1977, pl.9, figs.1–2; Fensome et al., 2019a, figs.17O–P.
NOW Tenua? Eisenack. Originally Cleistosphaeridium, subsequently Heterosphaeridium, thirdly Circulodinium?, fourthly (and now) Tenua Eisenack.
Questionable assignment: Fauconnier in Fauconnier and Masure (2004, p.115–116).
Age: Aptian–Albian.
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Diagnosis:
Shape: Pericyst subcircular; a short asymmetrical antapical prominence occurring on a few specimens. Endocyst as above, closely appressed to the pericyst. Pericoel not developed; compression dorso-ventral.
Phragma: Periphragm less than 0.5 μm thick, forming acuminate, distally pointed or weakly bifid processes up to 8 μm long and 0.5 to .0 μm wide, or flattened processes, wider basally and tapering distally, up to 10 μm long and up to 2.0 μm wide basally; process emplacement apparently non-paratabular; processes may or may not arise from a quasi-reticulate network of very low, narrow ridges formed of the periphragm, the ridges apparently also non-paratabular, process density highly variable, in places arranged in clusters. Surface ornamentation between processes scabrate to punctate. Endophragm less than 1.0 μm thick and unornamented.
Paratabulation: Archeopyle shape denotes four apical paraplates; other evidence for para tabulation lacking.
Archeopyle/operculum: Archeopyle formed by the loss of the four apical paraplates; operculum separating as a unit, simple and free, or lying in the archeopyle.
Formula: A.
Pericingulum/perisulcus: Pericingulum position determinable by parallel rows of widely spaced acuminate processes arising from a pair of narrow, low ridges formed from the periphragm; pericingulum positioned at the mid-latitude of the pericyst; pericingulum up to 7 μm wide and offset about one half of pericingular width. Evidence for a discernible perisulcus lacking.
Dimensions:
(15 μm measured specimens)
Pericyst length, 55-6 μm; pericyst width, 48-55 μm (maximum dimensions excluding processes). Maximum diameter on all reported specimens (see Brideaux , 1971; Brideaux and Mclntyre , 1976), 37-78 μm.
Pericyst length: 51μm pericyst width, 52 μm (excluding processes).
Affinities:
Cleistosphaeridium araneosum sp. nov. is distinguished from the comparable species, Cleistosphaeridium? aciculare Davey , 1969 and Cleistosphaeridium multispinosum (Singh) Brideaux, 1971 by possession of acuminate to weakly bifid spines arising from a low quasi-reticulate meshwork on the periphragm and by the much lower density of processes arising from the periphragm. Cleistosphaeridium multifurcatum (Deflandre) Davey et al., 1969, p. 16, differs in having a preponderance of distinctly bifid spines with broad columns arising from an obvermiculate surface ornament. Baltisphaeridium sp. A of Singh, 1971, p. 397, Plate 73, figures 9, 10, appears very similar, but Singh (1971, p. 397) characterizes the processes as " . .. splitting into numerous, slender, pointed spines at their outer ends...".
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Occurrence:
Rat Pass K-35: Upper sandstone division equivalent, sidewall cores and cuttings; Aptian. Stoney Core Hole F-42: Albian shale-siltstone division, Upper sandstone division and Upper shale-siltstone division equivalents, conventional core; Hauterivian to Middle Albian . Recorded previously from Middle and Upper Albian rocks of central and west-central Alberta, Canada (Brideaux , 1971) and from Middle Albian rocks on the Anderson Plain, northern Canadian mainland (Brideaux and Mclntyre , 1976). The suggestion of synonymy with Cleistosphaeridium? aciculare Davey (in part). is withdrawn and hence there is no confirmed Cenomanian record of Cleistosphaeridium araneosum sp. nov.
Circulodinium araneosum (Brideaux, 1977, p.22–23, pl.9, figs.1–3) Fauconnier in Fauconnier and Masure, 2004, p.115.
Holotype: Brideaux, 1977, pl.9, figs.1–2; Fensome et al., 2019a, figs.17O–P.
NOW Tenua? Eisenack. Originally Cleistosphaeridium, subsequently Heterosphaeridium, thirdly Circulodinium?, fourthly (and now) Tenua Eisenack.
Questionable assignment: Fauconnier in Fauconnier and Masure (2004, p.115–116).
Age: Aptian–Albian.
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Diagnosis:
Shape: Pericyst subcircular; a short asymmetrical antapical prominence occurring on a few specimens. Endocyst as above, closely appressed to the pericyst. Pericoel not developed; compression dorso-ventral.
Phragma: Periphragm less than 0.5 μm thick, forming acuminate, distally pointed or weakly bifid processes up to 8 μm long and 0.5 to .0 μm wide, or flattened processes, wider basally and tapering distally, up to 10 μm long and up to 2.0 μm wide basally; process emplacement apparently non-paratabular; processes may or may not arise from a quasi-reticulate network of very low, narrow ridges formed of the periphragm, the ridges apparently also non-paratabular, process density highly variable, in places arranged in clusters. Surface ornamentation between processes scabrate to punctate. Endophragm less than 1.0 μm thick and unornamented.
Paratabulation: Archeopyle shape denotes four apical paraplates; other evidence for para tabulation lacking.
Archeopyle/operculum: Archeopyle formed by the loss of the four apical paraplates; operculum separating as a unit, simple and free, or lying in the archeopyle.
Formula: A.
Pericingulum/perisulcus: Pericingulum position determinable by parallel rows of widely spaced acuminate processes arising from a pair of narrow, low ridges formed from the periphragm; pericingulum positioned at the mid-latitude of the pericyst; pericingulum up to 7 μm wide and offset about one half of pericingular width. Evidence for a discernible perisulcus lacking.
Dimensions:
(15 μm measured specimens)
Pericyst length, 55-6 μm; pericyst width, 48-55 μm (maximum dimensions excluding processes). Maximum diameter on all reported specimens (see Brideaux , 1971; Brideaux and Mclntyre , 1976), 37-78 μm.
Pericyst length: 51μm pericyst width, 52 μm (excluding processes).
Affinities:
Cleistosphaeridium araneosum sp. nov. is distinguished from the comparable species, Cleistosphaeridium? aciculare Davey , 1969 and Cleistosphaeridium multispinosum (Singh) Brideaux, 1971 by possession of acuminate to weakly bifid spines arising from a low quasi-reticulate meshwork on the periphragm and by the much lower density of processes arising from the periphragm. Cleistosphaeridium multifurcatum (Deflandre) Davey et al., 1969, p. 16, differs in having a preponderance of distinctly bifid spines with broad columns arising from an obvermiculate surface ornament. Baltisphaeridium sp. A of Singh, 1971, p. 397, Plate 73, figures 9, 10, appears very similar, but Singh (1971, p. 397) characterizes the processes as " . .. splitting into numerous, slender, pointed spines at their outer ends...".
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Occurrence:
Rat Pass K-35: Upper sandstone division equivalent, sidewall cores and cuttings; Aptian. Stoney Core Hole F-42: Albian shale-siltstone division, Upper sandstone division and Upper shale-siltstone division equivalents, conventional core; Hauterivian to Middle Albian . Recorded previously from Middle and Upper Albian rocks of central and west-central Alberta, Canada (Brideaux , 1971) and from Middle Albian rocks on the Anderson Plain, northern Canadian mainland (Brideaux and Mclntyre , 1976). The suggestion of synonymy with Cleistosphaeridium? aciculare Davey (in part). is withdrawn and hence there is no confirmed Cenomanian record of Cleistosphaeridium araneosum sp. nov.