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Gonyaulacysta fetchamensis
Gonyaulacysta fetchamensis Sarjeant, 1966
Now Cribroperidinium. Originally Gonyaulacysta, subsequently Millioudodinium, thirdly (and now) Cribroperidinium.
Holotype: Sarjeant, 1966, pl.15, figs.1-2, text-fig.33 and Jan du Chêne et al., 1986, pl.20, figs.1-4
Locus typicus: Fetcham Mill, Surrey, England
Stratum typicum: Cenomanian
Original diagnosis: Sarjeant, 1966, 128
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
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, forrning 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.
Now Cribroperidinium. Originally Gonyaulacysta, subsequently Millioudodinium, thirdly (and now) Cribroperidinium.
Holotype: Sarjeant, 1966, pl.15, figs.1-2, text-fig.33 and Jan du Chêne et al., 1986, pl.20, figs.1-4
Locus typicus: Fetcham Mill, Surrey, England
Stratum typicum: Cenomanian
Original diagnosis: Sarjeant, 1966, 128
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
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, forrning 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.