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Cribroperidinium fetchamense
From Fensome et al., 2019:
Cribroperidinium fetchamense (Sarjeant, 1966b, p.128,130, pl.15, figs.1–2; text-fig.33) Helenes, 1984, p.121. Holotype: Sarjeant, 1966b, pl.15, figs.1–2; text-fig.33; Helenes, 1984, text-figs.4A–B; Jan du Chêne et al., 1986a, pl.20, figs.1–4; Fensome et al., 1993a, figs.1–2 — p.1189. Originally Gonyaulacysta, subsequently Millioudodinium, thirdly (and now) Cribroperidinium. Age: early Cenomanian.
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Original diagnosis: Sarjeant, 1966, 128: Gonyaulacysta fetchamensis
A Gonyaulacysta having an ovoidal theca with strong, blunt apical horn formed by periphragm only. Tabulation 3-?4', 1a, 6'', 6c, 7''', 2p, 1''''; sutures in form of low but well-marked, rather fibrous crests giving rise occasionally to short, blunt spines. Cingulum narrow, strongly spiral; sulcus broad, sunken. Shell surface densely granular.
Dimensions: holotype: overall length 125 µm, breadth 108 µm; shell length 95 µm, breadth 98 µm; length of horn c.25 µm.
Original description: Sarjeant, 1966, p. 128-129: Gonyaulacysta fetchamensis
This species is extremely infrequent: of three specimens encountered, one (the holotype) is well preserved, the other two are severely damaged. The shell is broadly ovoidal, giving rise to a strong, blunt apical horn; this horn is formed by the periphragm only and constitutes what is effectively an apical pericoel. There are certainly three and possibly four apical plates, presence of a crest separating plates 3' and 4' being unconfirmed. Plate 1" is unusually large and club-shaped.
Six precingular plates are present, with plate 6" reduced to accommodate a subtriangular anterior intercalary plate. Seven postcingular plates are present.
Plates 1''' and 2''' are reduced to accommodate a large posterior intercalary plate, and plate 7''' is also reduced to accommodate a second, smaller intercalary plate. (The crest separating plates 5''' and 6''' is somewhat torn.) The antapex is occupied by a single plate of moderate size.
The cingulum is narrow, forming a laevorotatory spiral such that its two ends differ in antero-posterior position by almost three times its width. The ends of the cingulum are widely separated by a very broad sulcus, which widens further in its posterior portion. The crests are fibrous in nature, with close-set slits in places: they give rise to occasional short spines. In the holotype a broken line of "tubercles", like an embryonic crest, crosses plate 5''; this was not observed in the other specimens.
A precingular archaeopyle is formed by loss of the large plate 3''. In the holotype, the region round the archaeopyle is somewhat folded.
Cribroperidinium fetchamense (Sarjeant, 1966b, p.128,130, pl.15, figs.1–2; text-fig.33) Helenes, 1984, p.121. Holotype: Sarjeant, 1966b, pl.15, figs.1–2; text-fig.33; Helenes, 1984, text-figs.4A–B; Jan du Chêne et al., 1986a, pl.20, figs.1–4; Fensome et al., 1993a, figs.1–2 — p.1189. Originally Gonyaulacysta, subsequently Millioudodinium, thirdly (and now) Cribroperidinium. Age: early Cenomanian.
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Original diagnosis: Sarjeant, 1966, 128: Gonyaulacysta fetchamensis
A Gonyaulacysta having an ovoidal theca with strong, blunt apical horn formed by periphragm only. Tabulation 3-?4', 1a, 6'', 6c, 7''', 2p, 1''''; sutures in form of low but well-marked, rather fibrous crests giving rise occasionally to short, blunt spines. Cingulum narrow, strongly spiral; sulcus broad, sunken. Shell surface densely granular.
Dimensions: holotype: overall length 125 µm, breadth 108 µm; shell length 95 µm, breadth 98 µm; length of horn c.25 µm.
Original description: Sarjeant, 1966, p. 128-129: Gonyaulacysta fetchamensis
This species is extremely infrequent: of three specimens encountered, one (the holotype) is well preserved, the other two are severely damaged. The shell is broadly ovoidal, giving rise to a strong, blunt apical horn; this horn is formed by the periphragm only and constitutes what is effectively an apical pericoel. There are certainly three and possibly four apical plates, presence of a crest separating plates 3' and 4' being unconfirmed. Plate 1" is unusually large and club-shaped.
Six precingular plates are present, with plate 6" reduced to accommodate a subtriangular anterior intercalary plate. Seven postcingular plates are present.
Plates 1''' and 2''' are reduced to accommodate a large posterior intercalary plate, and plate 7''' is also reduced to accommodate a second, smaller intercalary plate. (The crest separating plates 5''' and 6''' is somewhat torn.) The antapex is occupied by a single plate of moderate size.
The cingulum is narrow, forming a laevorotatory spiral such that its two ends differ in antero-posterior position by almost three times its width. The ends of the cingulum are widely separated by a very broad sulcus, which widens further in its posterior portion. The crests are fibrous in nature, with close-set slits in places: they give rise to occasional short spines. In the holotype a broken line of "tubercles", like an embryonic crest, crosses plate 5''; this was not observed in the other specimens.
A precingular archaeopyle is formed by loss of the large plate 3''. In the holotype, the region round the archaeopyle is somewhat folded.