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Stanfordella exsanguia
Stanfordella exsanguia (Duxbury, 1977, p.35–36, pl.1, figs.6–7; text-fig.10) Helenes and Lucas-Clark, 1997, p.182. Emendation: Harding, 1990b, p.31–32, as Gonyaulacysta exsanguia.
Originally Gonyaulacysta, subsequently Millioudodinium?, thirdly (and now) Stanfordella.
Holotype: Duxbury, 1977, pl.1, fig.6; text-fig.10b; Jan du Chêne et al., 1986a, pl.40, figs.1–3.
Age: Hauterivian–Barremian.
Original diagnosis: Duxbury, 1977, p.35-36
A small species of Gonyaulacysta which is distinctly thin-walled with a finely granular body surface. A short, blunt apical horn is present. Tabulation ?4", 6", 6""", 1p, 1"""", outlined by low, denticulate sutural crests. Individual denticles fairly broad to slender, flared proximally and distally.
Observed Dimensions: Holotype 57x62 µm,. Overall 62(54)46x62(52)43 µm.
Affinities:
Duxbury, 1977, p. 36: The very thin-walled, highly transparent nature of this form, combined with the sutural crest denticulation sets it apart from all others. In the overall test form and thinness of the test walls, Gonyaulacysta exsanguia resembles Gonyaulacysta ordocava n. sp. The two species are easily distinguishable, however, due to the very distinctive, regularly perforate sutural crests of Gonyaulacysta ordocava.
Emended diagnosis: Harding, 1990, p. 31
Shape: Pentagonal ambitus, markedly angular. Apex produced into short, blunt, broad apical horn. Convex antapex. Greatest width across anterior cingular parasuture. Moderate dorso-ventral compression. Cyst extremely thin walled.
Phragma: Periphragm up to 0.3 µm thick, laevigate to very finely granulate, no intratabular tubercles.
Parasutural septa low (4-5 µm), distally variable from crenellated to bearing bifurcate spines. The characteristic feature of this species is the wide band of minute perforations along either side of each parasutural septum. These "pandasutural" bands are up to 6 µm wide, the individual perforations (effectively claustra) are < 0.1 µm in diameter. Endophragm is also very thin (0.1-0.2 µm thick), laevigate to faintly granular. Cavation is restricted to the apical horn with local suturocavation.
Paratabulation: Sexiform gonyaulacoid (S-type) formula: 2pr, 4", la, 6", 6c, 6"", 1""", lp, 5s. Inconspicuous incidental paraplate on dorsal surface; prominent porichnion on Q/lu/A triple junction; A small and bordering 6 which contacts lu.
Archaeopyle: Type P4, perioperculum and endoperculum lost as one unit, archaeopyle free.
Paracingulum: Strongly indented, laevorotatory, overhanging, displaced by 2;~2 cingulum widths.
Parasulcus: S-type, prominent, parasutures subdued. Claustrum developed in position of flagellar scar.
Remarks: This species is emended (after study of new topotype and additional material from each of the studied sections) to include full details of its paratabulation, to elucidate the variation in septal processes and to describe the diagnostic perforate "pandasutural" bands bordering the parasutural septa. This is a very thin walled species and is often found distorted, identification is however simple on the recognition of the perforate bands. No mention of this peculiar feature was made by Duxbury, 1977, as the feature is of too small a size to be resolved by LM.
This species displays a Jurassica paratabulation pattern, the apical Q/B arrangement including a single incidental paraplate. The ventral lu/li arrangement shows a contact between 6 and lu (Helenes, 1986).
Originally Gonyaulacysta, subsequently Millioudodinium?, thirdly (and now) Stanfordella.
Holotype: Duxbury, 1977, pl.1, fig.6; text-fig.10b; Jan du Chêne et al., 1986a, pl.40, figs.1–3.
Age: Hauterivian–Barremian.
Original diagnosis: Duxbury, 1977, p.35-36
A small species of Gonyaulacysta which is distinctly thin-walled with a finely granular body surface. A short, blunt apical horn is present. Tabulation ?4", 6", 6""", 1p, 1"""", outlined by low, denticulate sutural crests. Individual denticles fairly broad to slender, flared proximally and distally.
Observed Dimensions: Holotype 57x62 µm,. Overall 62(54)46x62(52)43 µm.
Affinities:
Duxbury, 1977, p. 36: The very thin-walled, highly transparent nature of this form, combined with the sutural crest denticulation sets it apart from all others. In the overall test form and thinness of the test walls, Gonyaulacysta exsanguia resembles Gonyaulacysta ordocava n. sp. The two species are easily distinguishable, however, due to the very distinctive, regularly perforate sutural crests of Gonyaulacysta ordocava.
Emended diagnosis: Harding, 1990, p. 31
Shape: Pentagonal ambitus, markedly angular. Apex produced into short, blunt, broad apical horn. Convex antapex. Greatest width across anterior cingular parasuture. Moderate dorso-ventral compression. Cyst extremely thin walled.
Phragma: Periphragm up to 0.3 µm thick, laevigate to very finely granulate, no intratabular tubercles.
Parasutural septa low (4-5 µm), distally variable from crenellated to bearing bifurcate spines. The characteristic feature of this species is the wide band of minute perforations along either side of each parasutural septum. These "pandasutural" bands are up to 6 µm wide, the individual perforations (effectively claustra) are < 0.1 µm in diameter. Endophragm is also very thin (0.1-0.2 µm thick), laevigate to faintly granular. Cavation is restricted to the apical horn with local suturocavation.
Paratabulation: Sexiform gonyaulacoid (S-type) formula: 2pr, 4", la, 6", 6c, 6"", 1""", lp, 5s. Inconspicuous incidental paraplate on dorsal surface; prominent porichnion on Q/lu/A triple junction; A small and bordering 6 which contacts lu.
Archaeopyle: Type P4, perioperculum and endoperculum lost as one unit, archaeopyle free.
Paracingulum: Strongly indented, laevorotatory, overhanging, displaced by 2;~2 cingulum widths.
Parasulcus: S-type, prominent, parasutures subdued. Claustrum developed in position of flagellar scar.
Remarks: This species is emended (after study of new topotype and additional material from each of the studied sections) to include full details of its paratabulation, to elucidate the variation in septal processes and to describe the diagnostic perforate "pandasutural" bands bordering the parasutural septa. This is a very thin walled species and is often found distorted, identification is however simple on the recognition of the perforate bands. No mention of this peculiar feature was made by Duxbury, 1977, as the feature is of too small a size to be resolved by LM.
This species displays a Jurassica paratabulation pattern, the apical Q/B arrangement including a single incidental paraplate. The ventral lu/li arrangement shows a contact between 6 and lu (Helenes, 1986).