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Gonyaulacysta orthoceras
Gonyaulacysta orthoceras (Eisenack, 1958a, p.388, pl.21, figs.3–11; pl.24, fig.1) Sarjeant, 1966b, p.121. Emendation: Sarjeant, 1985a, p.51,53, as Cribroperidinium orthoceras.
Now Cribroperidinium. Originally Gonyaulax, subsequently Gonyaulacysta, thirdly (and now) Cribroperidinium. Helenes, 1984, and Jan du Chêne et al., 1986, considered this to be a problematical species of Cribroperidinium. Lentin and Williams, 1973, retained this species in Cribroperidinium.
Taxonomic senior synonym: Gonyaulax (as Cribroperidinium) edwardsii, according to Davey and Verdier, 1971, Stover and Evitt, 1978, and Lentin and Williams, 1981. Below, 1981, Helenes, 1984, and Lentin and Williams, 1985, retained Cribroperidinium orthoceras as a separate species.
Holotype: Eisenack, 1958, pl.21, fig.5; Sarjeant, 1985, pl.1, figs.1,4, text-fig.1; Jan du Chêne et al., 1986, pl.24, figs.7-8
Locus typicus: N Germany
Stratum typicum: Aptian
Translation Eisenack, 1958: LPP
Translation Gocht, 1969: Geological Survey of Canada
Original diagnosis: Eisenack, 1958, p. 388-389: Gonyaulax orthoceras
Shell tick-walled, ovoidal with nearly hemisphaerical hypotheca with stong, thornlike apical horn of 1/4 of overall length. Girdle furrow spiral, bordered by low but thick sutures. Tabulation clearly visible; plate bounaries reflected by narrow, very low sutures which bear as the plates themselves short thorns or tubercles. Pylome trapezoidal, generally higher than wide.
Emended diagnosis: Sarjeant, 1966, p.121
A Gonyaulacysta having an ovoidal theca of moderate wall thickness, with strong, tapering apical horn accounting for about one-fifth to onequarter of overall length. Tabulation 4", 1a, 6", ?6c, 7""", 1p, 1""""; plate boundaries outlined by low crests bearing very abbreviate spinelets. Cingulum strongly spiral, of moderate breadth: sulcus broad and extending to antapex. Surface of shell granular to tuberculate.
Range of German specimens: overall length 70-105 Ám. Range of English specimens; overall length 80-115 Ám.
Emended description: Sarjeant, 1966, p. 122
Shell broadly ovoidal, with the hypotract rounded. The crests separating the four apical plates converge at the apex. Plate 1" occupies the anterior prolongation of the sulcus and is markedly elongate. Six precingular plates are present, with plate 6" very reduced to accommodate an anterior intercalary plate. Seven postcingular plates are present, plates 1""" and 2""" being reduced to accommodate a rather indistinctly demarcated posterior intercalary plate. A single polygonal plate occupies the antapex.
The cingulum forms a laevorotatory spiral such that its two ends differ in antero-posterior position by over three times its width. The number of cingular plates appears to be six, but the crests separating them are poorly marked. The sulcus is of moderate breadth and extends from mid-point on the epitract to the antapex. The shell wall is of moderate thickness and consists of two distinct layers. The apical horn is formed by the periphragm, the endophragm showing no outbulge; the horn is thus hollow and contains what is effectively an apical pericoel. The English specimens have a densely granular surface, but lack tubercles such as are present on the German specimens. A precingular archaeopyle, formed by loss of plate 3", is generally present.
Gocht, 1969, p.28:
Gonyaulacysta sp. aff. orthoceras (Eisenack, 1958)
The armor is ovoid to polygonal, with a distinctly granulate membrane of varying thickness. The cingulum is flat or only moderately indented; its boundaries and the sutures are usually accompanied by small wartlike or spinelike protuberances. The apical horn is long and straight.
This form vividly recalls G. orthoceras Eisenack from the Late Aptian, but can not be definitely identified.
Occurrence: Middle Oligocene.
Now Cribroperidinium. Originally Gonyaulax, subsequently Gonyaulacysta, thirdly (and now) Cribroperidinium. Helenes, 1984, and Jan du Chêne et al., 1986, considered this to be a problematical species of Cribroperidinium. Lentin and Williams, 1973, retained this species in Cribroperidinium.
Taxonomic senior synonym: Gonyaulax (as Cribroperidinium) edwardsii, according to Davey and Verdier, 1971, Stover and Evitt, 1978, and Lentin and Williams, 1981. Below, 1981, Helenes, 1984, and Lentin and Williams, 1985, retained Cribroperidinium orthoceras as a separate species.
Holotype: Eisenack, 1958, pl.21, fig.5; Sarjeant, 1985, pl.1, figs.1,4, text-fig.1; Jan du Chêne et al., 1986, pl.24, figs.7-8
Locus typicus: N Germany
Stratum typicum: Aptian
Translation Eisenack, 1958: LPP
Translation Gocht, 1969: Geological Survey of Canada
Original diagnosis: Eisenack, 1958, p. 388-389: Gonyaulax orthoceras
Shell tick-walled, ovoidal with nearly hemisphaerical hypotheca with stong, thornlike apical horn of 1/4 of overall length. Girdle furrow spiral, bordered by low but thick sutures. Tabulation clearly visible; plate bounaries reflected by narrow, very low sutures which bear as the plates themselves short thorns or tubercles. Pylome trapezoidal, generally higher than wide.
Emended diagnosis: Sarjeant, 1966, p.121
A Gonyaulacysta having an ovoidal theca of moderate wall thickness, with strong, tapering apical horn accounting for about one-fifth to onequarter of overall length. Tabulation 4", 1a, 6", ?6c, 7""", 1p, 1""""; plate boundaries outlined by low crests bearing very abbreviate spinelets. Cingulum strongly spiral, of moderate breadth: sulcus broad and extending to antapex. Surface of shell granular to tuberculate.
Range of German specimens: overall length 70-105 Ám. Range of English specimens; overall length 80-115 Ám.
Emended description: Sarjeant, 1966, p. 122
Shell broadly ovoidal, with the hypotract rounded. The crests separating the four apical plates converge at the apex. Plate 1" occupies the anterior prolongation of the sulcus and is markedly elongate. Six precingular plates are present, with plate 6" very reduced to accommodate an anterior intercalary plate. Seven postcingular plates are present, plates 1""" and 2""" being reduced to accommodate a rather indistinctly demarcated posterior intercalary plate. A single polygonal plate occupies the antapex.
The cingulum forms a laevorotatory spiral such that its two ends differ in antero-posterior position by over three times its width. The number of cingular plates appears to be six, but the crests separating them are poorly marked. The sulcus is of moderate breadth and extends from mid-point on the epitract to the antapex. The shell wall is of moderate thickness and consists of two distinct layers. The apical horn is formed by the periphragm, the endophragm showing no outbulge; the horn is thus hollow and contains what is effectively an apical pericoel. The English specimens have a densely granular surface, but lack tubercles such as are present on the German specimens. A precingular archaeopyle, formed by loss of plate 3", is generally present.
Gocht, 1969, p.28:
Gonyaulacysta sp. aff. orthoceras (Eisenack, 1958)
The armor is ovoid to polygonal, with a distinctly granulate membrane of varying thickness. The cingulum is flat or only moderately indented; its boundaries and the sutures are usually accompanied by small wartlike or spinelike protuberances. The apical horn is long and straight.
This form vividly recalls G. orthoceras Eisenack from the Late Aptian, but can not be definitely identified.
Occurrence: Middle Oligocene.