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Cassidium
From Fensome et al., 2019:
"Cassidium", Drugg, 1967, p.22.
Taxonomic senior synonym: Aptea, according to Fensome et al., 2019a, p.11.
Type: Harris, 1965, pl.27, fig.5, as Ovoidites fragilis.
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Original description: [Drugg, 1967]:
Description:
Test crudely circular in outline. Wall thick, rugulate to imperfectly reticulate. Tabulation present, consisting of apical and antapical plates. No girdle or longitudinal furrow present. The test opens by means of an apical archeopyle, the line of separation being zigzag.
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Modified description:
Stover and Evitt, 1978, p. 26:
Synopsis:
Cysts proximate, subspherical, gonyaulacacean; paratabulation indicated by parasutural grooves, surface rugulate to imperfectly reticulate; archeopyle apical, Type tA.
Description:
Shape: Subspherical.
Wall relationships: Autophragm only, relatively thick and rarely folded.
Wall features: Parasutural features may be any of the following: (1) narrow grooves, (2) depressed areas with ornamentation smaller than adjacent areas, or (3) narrow, unornamented areas. Autophragm with rugulate to imperfectly reticulate ornamentation.
Paratabulation: Indicated by parasutural features; gonyaulacacean, formula: 4`, 6", 5-6c, 5-6```, 0-1p, 1````.
Archeopyle: Apical, Type tA; principal archeopyle suture zigzag; operculum free; positions and shapes of apical paraplates indicated by notches along operculum margin and by distribution of ornamentation.
Paracingulum: Expressed moderately well on the dorsal surface by parasutural features; commonly not discernible ventrally.
Parasulcus: Not indicated, or only vaguely so, by poorly delimited area with subdued ornamentation.
Size: Intermediate.
Affinities:
Cassidium differs from Eisenackia in having a rugulate to imperfectly reticulate surface and generally less well-defined, shallower parasutural features. Anterior and posterior paraplates occur consistently in the parasulcus of Eisenackia, whereas these paraplates are not expressed on Cassidium.
"Cassidium", Drugg, 1967, p.22.
Taxonomic senior synonym: Aptea, according to Fensome et al., 2019a, p.11.
Type: Harris, 1965, pl.27, fig.5, as Ovoidites fragilis.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Drugg, 1967]:
Description:
Test crudely circular in outline. Wall thick, rugulate to imperfectly reticulate. Tabulation present, consisting of apical and antapical plates. No girdle or longitudinal furrow present. The test opens by means of an apical archeopyle, the line of separation being zigzag.
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Modified description:
Stover and Evitt, 1978, p. 26:
Synopsis:
Cysts proximate, subspherical, gonyaulacacean; paratabulation indicated by parasutural grooves, surface rugulate to imperfectly reticulate; archeopyle apical, Type tA.
Description:
Shape: Subspherical.
Wall relationships: Autophragm only, relatively thick and rarely folded.
Wall features: Parasutural features may be any of the following: (1) narrow grooves, (2) depressed areas with ornamentation smaller than adjacent areas, or (3) narrow, unornamented areas. Autophragm with rugulate to imperfectly reticulate ornamentation.
Paratabulation: Indicated by parasutural features; gonyaulacacean, formula: 4`, 6", 5-6c, 5-6```, 0-1p, 1````.
Archeopyle: Apical, Type tA; principal archeopyle suture zigzag; operculum free; positions and shapes of apical paraplates indicated by notches along operculum margin and by distribution of ornamentation.
Paracingulum: Expressed moderately well on the dorsal surface by parasutural features; commonly not discernible ventrally.
Parasulcus: Not indicated, or only vaguely so, by poorly delimited area with subdued ornamentation.
Size: Intermediate.
Affinities:
Cassidium differs from Eisenackia in having a rugulate to imperfectly reticulate surface and generally less well-defined, shallower parasutural features. Anterior and posterior paraplates occur consistently in the parasulcus of Eisenackia, whereas these paraplates are not expressed on Cassidium.