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Egmontodinium
From Williams et al., 2017:
[Egmontodinium, Gitmez and Sarjeant, 1972, p. 228-229
Type species: Egmontodinium polyplacophorum, Gitmez and Sarjeant, 1972 (pl.8, figs.1–2; pl.11, figs.5–6; text-figs.24A–B)]
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Original description: [Gitmez and Sarjeant, 1972]:
Description:
Proximate cyst, spherical to ovoidal.
Tabulation typically 4`, 5 or 6 ac., 6``, 6c, 6```, op, 2pv, 6pc, 1````; additional, very small platelets may be developed at crest nodes and the posterior tabulation is subject to some variation. No apical or other horns are developed. Crests or spinelets may arise from the sutures and spines may also be present, singly or in rows, on some plates.
Archaeopyle apical, formed by schism along the anterior circle; the operculum frequently remains attached.
Affinities:
Egmontodinium is distinguished from all other genera yet described in its tabulation. The plates surrounding the apex might be termed anterior intercalaries: the authors, however, feel that this would be inappropriate, since they are not merely interposed between existing reflected plate series but constitute an additional series. The new name "anterior circle plate" is thus coined for them. The plates surrounding the antapex are similarly designated "posterior circle plates", following the precedent of another Jurassic genus, Pluriarvalium.
The most comparable genus is Ellipsoidictyum Klement, 1960, whose complex tabulation was described in detail by Gocht, 1970 (p. 150-152): however, the tabulation of the epitract of this genus is markedly dissimilar and a close affinity cannot be considered probable.
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Modified description:
Stover and Evitt, 1978, p. 41-42:
Synopsis:
Cyst proximochorate, elongate ellipsoidal; paratabulation indicated by parasutural ridges; anterior and posterior circle paraplates present; archeopyle at apical end, normally attached ventrally, type uncertain.
Description:
Shape: Elongate ellipsoidal.
Wall relationships: Autophragm only.
Wall features: Parasutural ridges low to moderately high; smooth, or with short crestal features. Surface between ridges smooth or faintly ornamented.
Paratabulation: Indicated by parasutural features; formula: 4`, 5-6ac, 6``, 6c, 6```, 6pc, 1p,1````, 1s. Paraplates in anterior and posterior "circle" series are generally smaller than those in adjacent series.
Archeopyle: At apical end, type uncertain; principal archeopyle suture interpreted as transverse and dividing apical "circle" paraplates into approximately equal parts; operculum normally attached ventrally.
Paracingulum: Indicated by six transversely elongate rectangular paraplates.
Parasulcus: Narrow elongate area bounded by parasutural ridges; posterior sulcal paraplate delimited to the right of posterior intercalary paraplate.
Size: Intermediate.
Affinities:
Egmontodinium differs from all similarly shaped cysts in having "circle" paraplates.
[Egmontodinium, Gitmez and Sarjeant, 1972, p. 228-229
Type species: Egmontodinium polyplacophorum, Gitmez and Sarjeant, 1972 (pl.8, figs.1–2; pl.11, figs.5–6; text-figs.24A–B)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Gitmez and Sarjeant, 1972]:
Description:
Proximate cyst, spherical to ovoidal.
Tabulation typically 4`, 5 or 6 ac., 6``, 6c, 6```, op, 2pv, 6pc, 1````; additional, very small platelets may be developed at crest nodes and the posterior tabulation is subject to some variation. No apical or other horns are developed. Crests or spinelets may arise from the sutures and spines may also be present, singly or in rows, on some plates.
Archaeopyle apical, formed by schism along the anterior circle; the operculum frequently remains attached.
Affinities:
Egmontodinium is distinguished from all other genera yet described in its tabulation. The plates surrounding the apex might be termed anterior intercalaries: the authors, however, feel that this would be inappropriate, since they are not merely interposed between existing reflected plate series but constitute an additional series. The new name "anterior circle plate" is thus coined for them. The plates surrounding the antapex are similarly designated "posterior circle plates", following the precedent of another Jurassic genus, Pluriarvalium.
The most comparable genus is Ellipsoidictyum Klement, 1960, whose complex tabulation was described in detail by Gocht, 1970 (p. 150-152): however, the tabulation of the epitract of this genus is markedly dissimilar and a close affinity cannot be considered probable.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Evitt, 1978, p. 41-42:
Synopsis:
Cyst proximochorate, elongate ellipsoidal; paratabulation indicated by parasutural ridges; anterior and posterior circle paraplates present; archeopyle at apical end, normally attached ventrally, type uncertain.
Description:
Shape: Elongate ellipsoidal.
Wall relationships: Autophragm only.
Wall features: Parasutural ridges low to moderately high; smooth, or with short crestal features. Surface between ridges smooth or faintly ornamented.
Paratabulation: Indicated by parasutural features; formula: 4`, 5-6ac, 6``, 6c, 6```, 6pc, 1p,1````, 1s. Paraplates in anterior and posterior "circle" series are generally smaller than those in adjacent series.
Archeopyle: At apical end, type uncertain; principal archeopyle suture interpreted as transverse and dividing apical "circle" paraplates into approximately equal parts; operculum normally attached ventrally.
Paracingulum: Indicated by six transversely elongate rectangular paraplates.
Parasulcus: Narrow elongate area bounded by parasutural ridges; posterior sulcal paraplate delimited to the right of posterior intercalary paraplate.
Size: Intermediate.
Affinities:
Egmontodinium differs from all similarly shaped cysts in having "circle" paraplates.