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Canningia dicrypta
From Fensome et al., 2019:
Canningia? dicrypta (Gitmez and Sarjeant, 1972, p.225–226, pl.7, fig.6; text-fig.22) Below, 1981a, p.31. Holotype: Gitmez and Sarjeant, 1972, pl.7, fig.6; text-fig.22. Originally Meiourogonyaulax, subsequently Lithodinia, thirdly Meiourogonyaulax?, fourthly Canningia?, fifthly Escharisphaeridia. Questionable assignment: Below (1981a, p.31). Taxonomic senior synonym: Sentusidinium ringnesiorum, according to Wood et al. (2016, p.86–87). Age: early–late Kimmeridgian.
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Diagnosis:
Cyst subspherical to spherical, with the tabulation 4’, 6’’, 6c, 7’’’, 1p, 1’’’’, poorly marked by low ridges.
Cingulum more or less equatorial and cingular. Sulcus deep, short, confined to the hypotract, broadening towards the antapex.
Cyst wall thick and composed of two layers; thick endophragm and thin periphragm. The periphragm bulges out on the apex to form a blunt apical horn, a cavity being developed between two layers. Surface of the cyst is densely granular.
Apical archeopyle always present; sometimes the operculum remains attached to the shell, ventrally.
Dimensions:
Holotype – length (apex lacking) 40 μm, breadth 52 μm.
Range – overall length 70-90 μm, breadth 52-88 μm, length (apex lacking) 40-64 μm. Measured specimens 8 in number.
Description:
The spherical to subspherical cyst is divided into two equal parts by the moderately narrow cingulum. Both epitract and hypotract are dome-shaped; the epitract bears a small, blunt, hollow apical horn. Four apical and six precingular plates makeup the epitract; plate 1’ is elongate, the other apical plates are broader. Plates 1’’ and 6’’ are somewhat reduced and plates 2’’ and 5’’ are the largest of the precingular plates. Seven postcingular plates are present on the hypotract. Plates 1’’’ and 2’’’ are reduced because of the presence of a large intercalary plate (1p). Plates 3’’’,4’’’,5’’’ and 6’’’ are relatively large; plate 7’’’ is reduced. The single antapical plate (1’’’’) is quite large and convex.
The cingulum is poorly indicated, formed by six plates of variable size. The sulcus is deep, and its posterior portion, very wide.
An apical archaeopyle forms by loss of the apical plates.
Remarks:
Eight specimens (one from France, seven from England) were recorded. These specimens differ from other species of the genus in the character of their tabulation and possession of a hollow apical horn. In the presence of a seventh postcingular plate, this new species differs from the typical Meiourogonyaulax tabulation: however, it corresponds on all other respects.
Canningia? dicrypta (Gitmez and Sarjeant, 1972, p.225–226, pl.7, fig.6; text-fig.22) Below, 1981a, p.31. Holotype: Gitmez and Sarjeant, 1972, pl.7, fig.6; text-fig.22. Originally Meiourogonyaulax, subsequently Lithodinia, thirdly Meiourogonyaulax?, fourthly Canningia?, fifthly Escharisphaeridia. Questionable assignment: Below (1981a, p.31). Taxonomic senior synonym: Sentusidinium ringnesiorum, according to Wood et al. (2016, p.86–87). Age: early–late Kimmeridgian.
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Diagnosis:
Cyst subspherical to spherical, with the tabulation 4’, 6’’, 6c, 7’’’, 1p, 1’’’’, poorly marked by low ridges.
Cingulum more or less equatorial and cingular. Sulcus deep, short, confined to the hypotract, broadening towards the antapex.
Cyst wall thick and composed of two layers; thick endophragm and thin periphragm. The periphragm bulges out on the apex to form a blunt apical horn, a cavity being developed between two layers. Surface of the cyst is densely granular.
Apical archeopyle always present; sometimes the operculum remains attached to the shell, ventrally.
Dimensions:
Holotype – length (apex lacking) 40 μm, breadth 52 μm.
Range – overall length 70-90 μm, breadth 52-88 μm, length (apex lacking) 40-64 μm. Measured specimens 8 in number.
Description:
The spherical to subspherical cyst is divided into two equal parts by the moderately narrow cingulum. Both epitract and hypotract are dome-shaped; the epitract bears a small, blunt, hollow apical horn. Four apical and six precingular plates makeup the epitract; plate 1’ is elongate, the other apical plates are broader. Plates 1’’ and 6’’ are somewhat reduced and plates 2’’ and 5’’ are the largest of the precingular plates. Seven postcingular plates are present on the hypotract. Plates 1’’’ and 2’’’ are reduced because of the presence of a large intercalary plate (1p). Plates 3’’’,4’’’,5’’’ and 6’’’ are relatively large; plate 7’’’ is reduced. The single antapical plate (1’’’’) is quite large and convex.
The cingulum is poorly indicated, formed by six plates of variable size. The sulcus is deep, and its posterior portion, very wide.
An apical archaeopyle forms by loss of the apical plates.
Remarks:
Eight specimens (one from France, seven from England) were recorded. These specimens differ from other species of the genus in the character of their tabulation and possession of a hollow apical horn. In the presence of a seventh postcingular plate, this new species differs from the typical Meiourogonyaulax tabulation: however, it corresponds on all other respects.