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Aptea rotundata
From Fensome et al., 2019:
Aptea rotundata, (Cookson and Eisenack, 1961a, p.72, pl.12, figs.1–5) Fensome et al., 2019a, p.17.
Holotype: Cookson and Eisenack, 1961a, pl.12, fig.1; Fensome et al., 2019a, fig.12D.
Originally Canningia, subsequently Canningia?, thirdly Batiacasphaera, fourthly (and now) Aptea.
Taxonomic junior synonyms: Cyclonephelium paucimarginatum and Circulodinium vermiculatum, both according to Fensome et al. (2019a, p.17).
Age: Senonian.
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Original description as Canningia rotunda: [Cookson and Eisenack, 1961, p. 72]:
Description:
Shell nearly spherical in outline, mostly somewhat broader than long, flat in the present state of preservation, usually with a short broadly rounded apical horn. Antapex rounded or with a slight median prominance. Wall of variable thickness, c. 2-5 µm, closely covered with a dense indistinctly vermiculate pattern.
The shell opens by the complete detachment of the apex along an approximately straight line.
Dimensions:
Type: length 87 µm, breadth 90 µm.
Range: length 87-105 µm, breadth 90-132 µm.
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Comments from Fensome et al., 2019a:
Cookson and Eisenack (Citation1961, p. 72) described this species as having a wall ‘of variable thickness, c 2–5 μ, closely covered with a dense indistinctly vermiculate pattern’. The wall is thus single layered, with ornament of linear elements, and so fits with Aptea rather than Canningia. Although the epithet implies a bowl-shaped body, the holotype is asymmetrical, attesting to its areoligeracean affinity.
In describing Cyclonephelium paucimarginatum, Cookson and Eisenack (Citation1962) noted that the cyst has
a narrow, continuous circumferential zone in which the sculptural elements, in the form of short, wavy ridges, are densely arranged and often intertwined. The general surface … is finely to coarsely granular to vermiculate, the individual elements coarser and more widely spaced on the central region of each side.
Thus, the ornament is continuous, as is clear from the illustrations of the type material. We consider Cyclonephelium paucimarginatum to belong to Aptea, as a taxonomic junior synonym of Aptea rotundata, the type material of which also has vermiculate ornamentation.
Stover and Helby (Citation1987a, p. 230) described Circulodinium vermiculatum as lenticular (although their illustrations show mainly specimens with a regularly bowl-shaped ambitus), with very irregular vermiculate ornamentation that varies considerably over the cyst. They did not compare Circulodinium vermiculatum with Aptea rotundata, although we consider the two synonymous.
Stratigraphical occurrence. Cookson and Eisenack (Citation1961) recorded Aptea (as Canningia) rotundata from the Senonian of Australia. The term ‘Senonian’ is a former term for a Late Cretaceous epoch generally considered to encompass the Coniacean to Campanian interval but sometimes defined as including the Maastrichtian – we are uncertain as to the definition applied by Cookson and Eisenack (Citation1961). Cookson and Eisenack (Citation1962) described Cyclonephelium paucimarginatum from the ?late Albian to Cenomanian of Australia. The type material of Circulodinium vermiculatum is from the late Hauterivian to Barremian of offshore Western Australia.
Aptea rotundata, (Cookson and Eisenack, 1961a, p.72, pl.12, figs.1–5) Fensome et al., 2019a, p.17.
Holotype: Cookson and Eisenack, 1961a, pl.12, fig.1; Fensome et al., 2019a, fig.12D.
Originally Canningia, subsequently Canningia?, thirdly Batiacasphaera, fourthly (and now) Aptea.
Taxonomic junior synonyms: Cyclonephelium paucimarginatum and Circulodinium vermiculatum, both according to Fensome et al. (2019a, p.17).
Age: Senonian.
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Original description as Canningia rotunda: [Cookson and Eisenack, 1961, p. 72]:
Description:
Shell nearly spherical in outline, mostly somewhat broader than long, flat in the present state of preservation, usually with a short broadly rounded apical horn. Antapex rounded or with a slight median prominance. Wall of variable thickness, c. 2-5 µm, closely covered with a dense indistinctly vermiculate pattern.
The shell opens by the complete detachment of the apex along an approximately straight line.
Dimensions:
Type: length 87 µm, breadth 90 µm.
Range: length 87-105 µm, breadth 90-132 µm.
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Comments from Fensome et al., 2019a:
Cookson and Eisenack (Citation1961, p. 72) described this species as having a wall ‘of variable thickness, c 2–5 μ, closely covered with a dense indistinctly vermiculate pattern’. The wall is thus single layered, with ornament of linear elements, and so fits with Aptea rather than Canningia. Although the epithet implies a bowl-shaped body, the holotype is asymmetrical, attesting to its areoligeracean affinity.
In describing Cyclonephelium paucimarginatum, Cookson and Eisenack (Citation1962) noted that the cyst has
a narrow, continuous circumferential zone in which the sculptural elements, in the form of short, wavy ridges, are densely arranged and often intertwined. The general surface … is finely to coarsely granular to vermiculate, the individual elements coarser and more widely spaced on the central region of each side.
Thus, the ornament is continuous, as is clear from the illustrations of the type material. We consider Cyclonephelium paucimarginatum to belong to Aptea, as a taxonomic junior synonym of Aptea rotundata, the type material of which also has vermiculate ornamentation.
Stover and Helby (Citation1987a, p. 230) described Circulodinium vermiculatum as lenticular (although their illustrations show mainly specimens with a regularly bowl-shaped ambitus), with very irregular vermiculate ornamentation that varies considerably over the cyst. They did not compare Circulodinium vermiculatum with Aptea rotundata, although we consider the two synonymous.
Stratigraphical occurrence. Cookson and Eisenack (Citation1961) recorded Aptea (as Canningia) rotundata from the Senonian of Australia. The term ‘Senonian’ is a former term for a Late Cretaceous epoch generally considered to encompass the Coniacean to Campanian interval but sometimes defined as including the Maastrichtian – we are uncertain as to the definition applied by Cookson and Eisenack (Citation1961). Cookson and Eisenack (Citation1962) described Cyclonephelium paucimarginatum from the ?late Albian to Cenomanian of Australia. The type material of Circulodinium vermiculatum is from the late Hauterivian to Barremian of offshore Western Australia.