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Cleistosphaeridium araneosum
Cleistosphaeridium araneosum, Brideaux, 1977
NOW Circulodinium?. Originally Cleistosphaeridium, subsequently Heterosphaeridium, thirdly (and now) Circulodinium?.
Holotype: Brideaux, 1977, pl.9, 1-2
Locus typicus: Richardson Mountains, District of Mackenzie, Canada
Stratum typicum: Aptian-Albian
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Original description: [Brideaux, 1977, p. 22-23]:
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 1.0 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 paratabulation 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.
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:
Pericyst length, 55-63 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.
Affinities:
Cleistosphaeridium araneosum is distinguished from the comparable species Cleistosphaeridium? acilare 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 differs in having a preponderance of distinctly bifid spines with broad columns arising from an obvermiculate surface ornament. Baltisphaeridium sp. A of Singh, 1971, appears very similar, but Singh (1971, p. 397) characterizes the processes as "... splitting into numerous, slender, pointed spines at their outer ends...".
NOW Circulodinium?. Originally Cleistosphaeridium, subsequently Heterosphaeridium, thirdly (and now) Circulodinium?.
Holotype: Brideaux, 1977, pl.9, 1-2
Locus typicus: Richardson Mountains, District of Mackenzie, Canada
Stratum typicum: Aptian-Albian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Brideaux, 1977, p. 22-23]:
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 1.0 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 paratabulation 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.
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:
Pericyst length, 55-63 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.
Affinities:
Cleistosphaeridium araneosum is distinguished from the comparable species Cleistosphaeridium? acilare 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 differs in having a preponderance of distinctly bifid spines with broad columns arising from an obvermiculate surface ornament. Baltisphaeridium sp. A of Singh, 1971, appears very similar, but Singh (1971, p. 397) characterizes the processes as "... splitting into numerous, slender, pointed spines at their outer ends...".