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Charlesdowniea fusiformis
Charlesdowniea fusiformis, (Mao Shaozhi and Norris, 1988), Lentin and Williams, 1993
Originally Kisselevia, subsequently Charlesdowniea, thirdly (and now) Talladinium.
Holotype: Mao Shaozhi and Norris, 1988, pl.13, fig.3
Locus typicus: Wuluokeqiate section, China
Stratum typicum: Early Oligocene
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Original description as Kisselovia fusiformis: [Mao Shaozhi and Norris, 1988, p. 49-50]:
Diagnosis:
Cyst proximochorate, typically cornucavate, rhombic to fusiform at ambitus; with an indistinct apical, one antapical, and two cingular horns. Epitract commonly shorter than hypotract. Periphragm bearing the intratabular processes arranged in simulate complexes and also distributed haphazardly within complexes. Neighbouring processes may be connected distally by trabeculae. Process complexes masked by very thin perforate membranes from three directions. Endoblast asymmetrically rhombic, protruding more into the hypotract than the epitract.
Archeopyle intercalary, type (I)a, quadra 2a style; operculum seldom free.
Description:
Epitract triangular, with a triangular apical horn merging into the two sides imperceptibly. Hypotract also triangular, with a triangular antapical horn commonly sharper than the apical horn; sometimes the antapical horn divided distally into two small subsidiary, closely adjacent horns, the left being longer and more pointed than the right. The two cingular horns variable in length (usually 8 to 12.5 µm, up to 17 µm) and shape (from domelike to nipplelike), commonly with broad bases and rounded ends.
Both periphragm and endophragm smooth, the cornucavate pericoels connected by very narrow ambital pericoels or none at all.
Processes mainly simple and isolated, typically capitate, rarely bifurcate and aculeate distally, expanded proximally, in rare cases the two neighbouring processes connected proximally. They are usually 0.5 to 1 µm in width and 8 to 10 µm in length. Masked by very thin and perforate membranes, the simulate process complexes assume the outline of underlying plates.
However, the precise tabulation formula cannot be deciphered from them, because of the long and randomly oriented processes just within the plate boundary.
Cingulum faintly indicated by the alignment of processes along the borders and a lack of processes within the cingulum.
Archaeopyle only occasionally discernible; the operculum commonly attached anteriorly and slightly open posteriorly, the sutures often obscured by the long processes.
Dimensions:
Length 117 - 162.5 µm ( holotype 120 µm), width 90 - 125µm (holotype 95 µm).
Affinities:
Kisselovia fusiformis is distinguished by its elongate rhombic pericyst with epitract shorter than the hypotract and by its either indistinct or distally rounded horns. K. variabilis Bujak, 1980, also has a rhombic pericyst with a longer hypotract than the epitract; however, it is broader than long and has more complicated process complexes.
Originally Kisselevia, subsequently Charlesdowniea, thirdly (and now) Talladinium.
Holotype: Mao Shaozhi and Norris, 1988, pl.13, fig.3
Locus typicus: Wuluokeqiate section, China
Stratum typicum: Early Oligocene
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Original description as Kisselovia fusiformis: [Mao Shaozhi and Norris, 1988, p. 49-50]:
Diagnosis:
Cyst proximochorate, typically cornucavate, rhombic to fusiform at ambitus; with an indistinct apical, one antapical, and two cingular horns. Epitract commonly shorter than hypotract. Periphragm bearing the intratabular processes arranged in simulate complexes and also distributed haphazardly within complexes. Neighbouring processes may be connected distally by trabeculae. Process complexes masked by very thin perforate membranes from three directions. Endoblast asymmetrically rhombic, protruding more into the hypotract than the epitract.
Archeopyle intercalary, type (I)a, quadra 2a style; operculum seldom free.
Description:
Epitract triangular, with a triangular apical horn merging into the two sides imperceptibly. Hypotract also triangular, with a triangular antapical horn commonly sharper than the apical horn; sometimes the antapical horn divided distally into two small subsidiary, closely adjacent horns, the left being longer and more pointed than the right. The two cingular horns variable in length (usually 8 to 12.5 µm, up to 17 µm) and shape (from domelike to nipplelike), commonly with broad bases and rounded ends.
Both periphragm and endophragm smooth, the cornucavate pericoels connected by very narrow ambital pericoels or none at all.
Processes mainly simple and isolated, typically capitate, rarely bifurcate and aculeate distally, expanded proximally, in rare cases the two neighbouring processes connected proximally. They are usually 0.5 to 1 µm in width and 8 to 10 µm in length. Masked by very thin and perforate membranes, the simulate process complexes assume the outline of underlying plates.
However, the precise tabulation formula cannot be deciphered from them, because of the long and randomly oriented processes just within the plate boundary.
Cingulum faintly indicated by the alignment of processes along the borders and a lack of processes within the cingulum.
Archaeopyle only occasionally discernible; the operculum commonly attached anteriorly and slightly open posteriorly, the sutures often obscured by the long processes.
Dimensions:
Length 117 - 162.5 µm ( holotype 120 µm), width 90 - 125µm (holotype 95 µm).
Affinities:
Kisselovia fusiformis is distinguished by its elongate rhombic pericyst with epitract shorter than the hypotract and by its either indistinct or distally rounded horns. K. variabilis Bujak, 1980, also has a rhombic pericyst with a longer hypotract than the epitract; however, it is broader than long and has more complicated process complexes.