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Ctenidodinium kettonense
Ctenidodinium kettonensis (Sarjeant, 1976) Stover and Evitt, 1978
Now Korystocysta. Originally Dichadogonyaulax, subsequently Ctenidodinium, thirdly (and now) Korystocysta.
Taxonomic senior synonym: Dichadogonyaulax (now Korystocysta) gochtii, according to Riley and Fenton (1982, p.199) and Herngreen et al. (2000, p.50).
Taxonomic senior synonyms: Gonyaulax (now Korystocysta) pachyderma and Leptodinium (subsequently Korystocysta) norrisii, 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 Korystocysta kettonensis.
Holotype: Sarjeant, 1976, pl.1, fig.1-2
Locys typicus: Great oolite limestone, Lincolnshire, England
Stratum typicum: Bathonian
Original description: Sarjeant, 1976, p. 13-15: Dichadogonyaulax kettonensis
Diagnosis: A species of Dichadogonyaulax of broadly ovoidal to rounded-polygonal
amibitus, with a short, blunt, mamelon-like apical horn. Epitract hemi-ovoidal to rounded-conical, smaller than the hypotract; hypotract hemi-ovoidal, somewhat flattened at the antapex. Reflected tabulation: 1 pre-apical, 4", 1a, 6"", 6c, 7""", 1p, 1pv, 1"""": sulcus divided into at least 3 plates (as, ms, ps) and having a central depression exhibiting flagellar marks. Plate-areas 6c and 1""" both impinge markedly upon the sulcus; plate-areas 1""" and 2""" are separated from the antapex by the large posterior intercalary plate-area, being both reduced (1""" markedly so) in consequence. Plate-area 7""" and the posterior sulcal plate-area are of closely similar size and shape, both being separated from the antapex by the posterior ventral plate-area. Crests low fairly thick, giving rise to blunt spinelets. Plate-area 4""", and perhaps other plate-areas, may exhibit intratabular crests paralleling those bounding the plate-area. Cingulum moderately broad, strongly laevorotatory, Archaeopyle epitractal, the epitract frequently remaining attached to the hypotract ventrally: more often, though, the hemicysts separate, the epitract sometimes losing precingular plate-areas by further schism along accessory archaeopyle sutures.
Dimensions: Holotype: overall length 50 Ám, length of apical horn c. 3 Ám, overall breadth 45 Ám.
Description (annotated): A minute anterior intercalary plate-area is present on the dorsal surface, at the junction of plate-areas 2" and 3" with plate-area 3"". All six precingular plate-areas are quite large, plate-area 3"" (on the dorsal surface) being the largest of the series. The relatively broad cingulum is strongly helicoid, its two ends differing in anteroposterior position by more than the furrow"s breadth. It is divided into six plate-areas; the last of these, 6c, is almost quadrate, its left hand section protruding into the sulcus. The epitractal portion of the sulcus (the anterior sulcal plate-area) is polygonal, broadest at the cyst equator. The sulcus narrows abruptly at midpoint, being constricted by plate-areas 6c and 1""", and is here sunken, usually exhibiting clear flagellar marks. .... The hypotractal portion of the sulcus is narrower than the epitractal portion, consisting of a single (posterior sulcal) plate-area. Of the seven postcingular plate-areas, 3""" to 5""" are quite large, 4""" being the indeed the largest of all the plate-areas. ...The cyst wall is of moderate thickness (up to 2 Ám) and bears a dense overall ornament of granules and punctae, giving the periphragm an almost shagreen-like appearance. The crest are well-marked and bear very short, closely to widely spaced spinelets.
Affinities:
Sarjeant, 1976, p. 15: Dichadogonyaulax kettonensis
Of the described species of this genus, Dichadogonyaulax kettonensis is comparable in morphology only to D. gochtii sp. nov. It differs from that species in its greater proportionate breadth and coarser ornament, the presence of ornament over the whole sulcal surface, and the detail of the ventral tabulation (in particular the shape and position of plate-areas 7""" and ps). Specimens of D. kettonensis seen in dorsal orientation may be perhaps distinguished by the development of intratabular crests, but I consider this an unsafe criterion and would stress that identification should be always confirmed by careful examination of the ventral tabulation.
Now Korystocysta. Originally Dichadogonyaulax, subsequently Ctenidodinium, thirdly (and now) Korystocysta.
Taxonomic senior synonym: Dichadogonyaulax (now Korystocysta) gochtii, according to Riley and Fenton (1982, p.199) and Herngreen et al. (2000, p.50).
Taxonomic senior synonyms: Gonyaulax (now Korystocysta) pachyderma and Leptodinium (subsequently Korystocysta) norrisii, 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 Korystocysta kettonensis.
Holotype: Sarjeant, 1976, pl.1, fig.1-2
Locys typicus: Great oolite limestone, Lincolnshire, England
Stratum typicum: Bathonian
Original description: Sarjeant, 1976, p. 13-15: Dichadogonyaulax kettonensis
Diagnosis: A species of Dichadogonyaulax of broadly ovoidal to rounded-polygonal
amibitus, with a short, blunt, mamelon-like apical horn. Epitract hemi-ovoidal to rounded-conical, smaller than the hypotract; hypotract hemi-ovoidal, somewhat flattened at the antapex. Reflected tabulation: 1 pre-apical, 4", 1a, 6"", 6c, 7""", 1p, 1pv, 1"""": sulcus divided into at least 3 plates (as, ms, ps) and having a central depression exhibiting flagellar marks. Plate-areas 6c and 1""" both impinge markedly upon the sulcus; plate-areas 1""" and 2""" are separated from the antapex by the large posterior intercalary plate-area, being both reduced (1""" markedly so) in consequence. Plate-area 7""" and the posterior sulcal plate-area are of closely similar size and shape, both being separated from the antapex by the posterior ventral plate-area. Crests low fairly thick, giving rise to blunt spinelets. Plate-area 4""", and perhaps other plate-areas, may exhibit intratabular crests paralleling those bounding the plate-area. Cingulum moderately broad, strongly laevorotatory, Archaeopyle epitractal, the epitract frequently remaining attached to the hypotract ventrally: more often, though, the hemicysts separate, the epitract sometimes losing precingular plate-areas by further schism along accessory archaeopyle sutures.
Dimensions: Holotype: overall length 50 Ám, length of apical horn c. 3 Ám, overall breadth 45 Ám.
Description (annotated): A minute anterior intercalary plate-area is present on the dorsal surface, at the junction of plate-areas 2" and 3" with plate-area 3"". All six precingular plate-areas are quite large, plate-area 3"" (on the dorsal surface) being the largest of the series. The relatively broad cingulum is strongly helicoid, its two ends differing in anteroposterior position by more than the furrow"s breadth. It is divided into six plate-areas; the last of these, 6c, is almost quadrate, its left hand section protruding into the sulcus. The epitractal portion of the sulcus (the anterior sulcal plate-area) is polygonal, broadest at the cyst equator. The sulcus narrows abruptly at midpoint, being constricted by plate-areas 6c and 1""", and is here sunken, usually exhibiting clear flagellar marks. .... The hypotractal portion of the sulcus is narrower than the epitractal portion, consisting of a single (posterior sulcal) plate-area. Of the seven postcingular plate-areas, 3""" to 5""" are quite large, 4""" being the indeed the largest of all the plate-areas. ...The cyst wall is of moderate thickness (up to 2 Ám) and bears a dense overall ornament of granules and punctae, giving the periphragm an almost shagreen-like appearance. The crest are well-marked and bear very short, closely to widely spaced spinelets.
Affinities:
Sarjeant, 1976, p. 15: Dichadogonyaulax kettonensis
Of the described species of this genus, Dichadogonyaulax kettonensis is comparable in morphology only to D. gochtii sp. nov. It differs from that species in its greater proportionate breadth and coarser ornament, the presence of ornament over the whole sulcal surface, and the detail of the ventral tabulation (in particular the shape and position of plate-areas 7""" and ps). Specimens of D. kettonensis seen in dorsal orientation may be perhaps distinguished by the development of intratabular crests, but I consider this an unsafe criterion and would stress that identification should be always confirmed by careful examination of the ventral tabulation.