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Dichadogonyaulax gochtii
Dichadogonyaulax gochtii Sarjeant, 1976
Now Korystocysta. Originally Dichadogonyaulax, subsequently Ctenidodinium, thirdly (and now) Korystocysta.
Taxonomic junior synonym: Dichadogonyaulax (subsequently Korystocysta) kettonensis, according to Riley and Fenton (1982, p.199), Dodekova (1990), and Herngreen et al. (2000, p.50).
Taxonomic senior synonym: Gonyaulax (now Korystocysta) pachyderma, by implication in Conway (1990, p.35), who considered Dichadogonyaulax (as Korystocysta) kettonensis to be the senior name - however, Lentin and Williams (1993, p.374) retained Dichadogonyaulax (as Korystocysta) gochtii.
Holotype: Sarjeant, 1976, pl.2, fig.1, textfigs.2A-B
Paratype: Sarjeant, 1976
Locus typicus: Ketton Grange Quarry, Ketton, Lincolnshire, England.
Stratum typicum: Bathonian
Original diagnosis: Sarjeant, 1976, p. 11
A species of Dichadogonyaulax of ovoidal to rounded-polygonal ambitus, with an abbreviate apical horn. Epitract a hemiovoid, somewhat smaller than the hypotract; hypotract also a hemiovoid, but exhibiting slight antapical flattening. Reflected tabulation 1 preapical, 4", 6", 7c, 7""", 1p, 1pv, 1""""; an anterior sulcal plate-area may be developed, but other~vise the sulcus is not clearly divided into plate-areas, Plate-areas 1""" and 2""" are separated from the antapex by an unusually elongate posterior intercalary plate-area. Plate area 7""" is also reduced, it and the sulcus being separated from the antapex by the posterior ventral plate-area. Cingulum strongly laevorotatory. The central part of the sulcus is distinctly sunken and exhibits flagellar marks.
Crests clearly marked by low ridges, irregularly crenulate or denticulate. Archaeopyle epitractal, the epitract frequently remaining attached to the hypotract ventrally; more often the hemicysts separate, the epitract sometimes losing precingular plate-areas by further schism along accessory archaeopyle sutures.
Original description: Sarjeant, 1976, p. 11-12
The apical horn is quite short, relatively blunt; the crest surroullding the pre-apical plate which forms its tip may give the horn a mammillate or even trifid appearance in some views. Four apical plate-areas are developed, plate-area 1" occupying the anterior prolongation of the sulcus. A minute anterior intercalary plate-area is present on the dorsal surface at the junction of plate-areas 2", 3", and 3"; this can be seen only in exceptionally favourable specimens. All six precingular plate-areas are quite large; plate-area 3"", occupying the dorsal surface, is the larclest of the series.
The cingulum is of moderate breadth and is markedly helicoid, its two ends differing in anteroposterior position by more than the furrow"s breadth. It is divided into seven plate-areas, the seventh being small and quadrate. The sulcus is broad but short, extending roughly from midpoint on the epitract to midpoint on the hypotract: its central portion is markedly sunken and exhibits two clear flagellar marks.
Seven postcingular plate-areas are developed. Plate-area 1""" is very small and elongate, plate-area 2""" larger and shield-shaped. Plate-areas 3""" to 6""" are all relatively large, with 4""" the largest of the series, but plate-area 7""" is again small and elongate. The posterior ventral plate-area, separating 7""" and the sulcus from the antapex, is large and almost quadrate: the posterior intercalary plate-area is elongate, with an anterior prong reaching to the mid-ventral region where it forms the posterior margin of plate-area 1""". Plate area 1"""" is polygonal and of moderate size.
The cyst wall is of moderate thickness, punctate except for the sulcus, the posterior two-thirds of which are laevigate. Its anterior third, which separates off with the epitract during excystment, is however distinctly punctate and might perhaps be appropriately distinguished as an anterior sulcal plate area. The crests are low but clear, exhibiting an irregular distal crenulation which, in some instances, approaches a low-amplitude denticulation.
Dimensions. Holotype: overall length 52 Ám, length of apical horn c. 3 Ám, overall breadth 44 Ám. Paratype (epitract): length not measurable, breadth 49 Ám.
Range: Overall length 50,5-78 Ám (mean 62 Ám), length of horn 1.5-6 Ám (mean 3 Ám), overall breadth 42-57,5 Ám (mean 51 Ám).
Affinities:
Sarjeant, 1976, p. 12: In its overall morphology, Dichadogonyaulax gochtii differs markedly from all species previously assigned to this genus. The tabulation pattern is comparable with that of Gonyaulacysta aldorfensis Gocht, 1970, but the wall structure and mode of archaeopyle formation are quite dissimilar.
Now Korystocysta. Originally Dichadogonyaulax, subsequently Ctenidodinium, thirdly (and now) Korystocysta.
Taxonomic junior synonym: Dichadogonyaulax (subsequently Korystocysta) kettonensis, according to Riley and Fenton (1982, p.199), Dodekova (1990), and Herngreen et al. (2000, p.50).
Taxonomic senior synonym: Gonyaulax (now Korystocysta) pachyderma, by implication in Conway (1990, p.35), who considered Dichadogonyaulax (as Korystocysta) kettonensis to be the senior name - however, Lentin and Williams (1993, p.374) retained Dichadogonyaulax (as Korystocysta) gochtii.
Holotype: Sarjeant, 1976, pl.2, fig.1, textfigs.2A-B
Paratype: Sarjeant, 1976
Locus typicus: Ketton Grange Quarry, Ketton, Lincolnshire, England.
Stratum typicum: Bathonian
Original diagnosis: Sarjeant, 1976, p. 11
A species of Dichadogonyaulax of ovoidal to rounded-polygonal ambitus, with an abbreviate apical horn. Epitract a hemiovoid, somewhat smaller than the hypotract; hypotract also a hemiovoid, but exhibiting slight antapical flattening. Reflected tabulation 1 preapical, 4", 6", 7c, 7""", 1p, 1pv, 1""""; an anterior sulcal plate-area may be developed, but other~vise the sulcus is not clearly divided into plate-areas, Plate-areas 1""" and 2""" are separated from the antapex by an unusually elongate posterior intercalary plate-area. Plate area 7""" is also reduced, it and the sulcus being separated from the antapex by the posterior ventral plate-area. Cingulum strongly laevorotatory. The central part of the sulcus is distinctly sunken and exhibits flagellar marks.
Crests clearly marked by low ridges, irregularly crenulate or denticulate. Archaeopyle epitractal, the epitract frequently remaining attached to the hypotract ventrally; more often the hemicysts separate, the epitract sometimes losing precingular plate-areas by further schism along accessory archaeopyle sutures.
Original description: Sarjeant, 1976, p. 11-12
The apical horn is quite short, relatively blunt; the crest surroullding the pre-apical plate which forms its tip may give the horn a mammillate or even trifid appearance in some views. Four apical plate-areas are developed, plate-area 1" occupying the anterior prolongation of the sulcus. A minute anterior intercalary plate-area is present on the dorsal surface at the junction of plate-areas 2", 3", and 3"; this can be seen only in exceptionally favourable specimens. All six precingular plate-areas are quite large; plate-area 3"", occupying the dorsal surface, is the larclest of the series.
The cingulum is of moderate breadth and is markedly helicoid, its two ends differing in anteroposterior position by more than the furrow"s breadth. It is divided into seven plate-areas, the seventh being small and quadrate. The sulcus is broad but short, extending roughly from midpoint on the epitract to midpoint on the hypotract: its central portion is markedly sunken and exhibits two clear flagellar marks.
Seven postcingular plate-areas are developed. Plate-area 1""" is very small and elongate, plate-area 2""" larger and shield-shaped. Plate-areas 3""" to 6""" are all relatively large, with 4""" the largest of the series, but plate-area 7""" is again small and elongate. The posterior ventral plate-area, separating 7""" and the sulcus from the antapex, is large and almost quadrate: the posterior intercalary plate-area is elongate, with an anterior prong reaching to the mid-ventral region where it forms the posterior margin of plate-area 1""". Plate area 1"""" is polygonal and of moderate size.
The cyst wall is of moderate thickness, punctate except for the sulcus, the posterior two-thirds of which are laevigate. Its anterior third, which separates off with the epitract during excystment, is however distinctly punctate and might perhaps be appropriately distinguished as an anterior sulcal plate area. The crests are low but clear, exhibiting an irregular distal crenulation which, in some instances, approaches a low-amplitude denticulation.
Dimensions. Holotype: overall length 52 Ám, length of apical horn c. 3 Ám, overall breadth 44 Ám. Paratype (epitract): length not measurable, breadth 49 Ám.
Range: Overall length 50,5-78 Ám (mean 62 Ám), length of horn 1.5-6 Ám (mean 3 Ám), overall breadth 42-57,5 Ám (mean 51 Ám).
Affinities:
Sarjeant, 1976, p. 12: In its overall morphology, Dichadogonyaulax gochtii differs markedly from all species previously assigned to this genus. The tabulation pattern is comparable with that of Gonyaulacysta aldorfensis Gocht, 1970, but the wall structure and mode of archaeopyle formation are quite dissimilar.