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Cribroperidinium tenuitabulatum
From Fensome et al., 2019:
Cribroperidinium tenuitabulatum (Gerlach, 1961, p.159, pl.25, figs.10–11; text-figs.1–3) Helenes, 1984, p.124. Emendation: Sarjeant, 1984b, p.76, as Rhynchodiniopsis tenuitabulata. Holotype: Gerlach, 1961, pl.25, figs.10–11, lost according to Sarjeant (1984b, p.78. Lectotype: Sarjeant, 1984b, pl.2, fig.3, designated by Sarjeant (1984b, p.78) Taxonomic senior synonym: Gymnodinium (as and now Apteodinium) australiense, according to Fensome et al. (2016b, p.27). Originally Gonyaulax, subsequently Gonyaulacysta, thirdly Millioudodinium, fourthly (and subsequently) Cribroperidinium, fifthly RhynchodiniopsisAge: middle Oligocene–Middle Miocene.
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Original description Gerlach, 1961:
Holotype: Pr 1170/10 (269) Plate 25, Fig. 10 and 11
Paratypes: Pr1170/11 (283), Pr1170/12 (280)
Locus typicus: Bohrung Emsburen 7.
Stratum typicum: Mid-Oligocene
Derivation of the name: Reference to the poorly developed tabulation.
Remarks: The genus Gounyaulax has not yet been described as a representative of Tertiary sediments. This fact is surprising in itself, because these highly developed forms already occur among the first known dinoflagellates from the Middle Dogger and remain quite common in the Malmian and Cretaceous periods. They are also represented by many species in recent times. Thus, their occurrence in Tertiary strata of northwest Germany can close a gap.
Diagnosis:
Shell thin-walled, squat spheroidal, with a short, blunt apical horn. Tabulation scheme: 4', 6", 6"', 1p, 1ppl.
1'"'. Plates slanted by low, narrow ridges. Girdle furrow spiral with a displacement of approximately 1.5 furrow widths.
Membrane finely granulated.
Description:
The epitheca appears hemispherical in outline. A short, relatively broad horn protrudes at the apex, which tapers distally and is composed of four raised apical plates. Only a few specimens reveal the tabulation in detail. In order to define it clearly, the epitheca and hypotheca of various shells had to be examined. Of the apical plates, the 1' lies in the extension of the longitudinal furrow.
It is bordered laterally by the squat, trapezoidal 4'.
In the apical region of the dorsal side lie the two smaller apical plates 2' and 3'. Their outline is roughly triangular. The trapezoidal plates 2'', 3'', and 4" form the dorsal whorl, while the trapezoidal plates 1", 5", and 6" lie ventrally. The precingulates mentioned are relatively large, except for the 6", which is reduced to one-third of the other plates. Quite often, a trapezoidal pyloma is found in place of the 3".
The spiral girdle groove divides the theca into two almost equal parts. It is probably composed of six plates, which, like the others, are bordered by low, narrow hyaline ridges.
Ventrally, the ends of the girdle groove are offset by approximately 1.5 groove widths. The outer shell is slightly notched laterally in the region of the girdle groove. The longitudinal groove shows a clear division into two plates, as can be observed in most fossil Gonyaulax species. A polygonal lower plate (ppl) is separated from the relatively narrow longitudinal groove, bordered by curved sides. The almost hemispherical hypogeum consists of six postcingulates, one accessory plate (1p), and a large polygonal antapical plate. Characteristic of many Gonyaulax species is the ventrally located, strongly reduced, approximately elongated-polygonal 1"'. The elongated 1p is inserted into the acute angle it forms with the trapezoidal 2"', toward the antapex. Between 1"', 1p, and 3"' lies the 2'", which is also still fully developed, while the large, trapezoidal 3'", 4"", and 5'" form the dorsal whorl. The 6'' is located ventrally and is somewhat reduced in size. The antapex is composed of a large, polygonal and convex antapical plate.
The membrane of theca is finely granulated, very delicate, and brownish-yellow in color. The suture ridges appear somewhat lighter.
Affinities:
The present Gonyaulax species represents one of the relatively unornamented types of this genus, in which the sutures are only covered with narrow, entire ridges and not with branched protuberances or serrated crests. No analogies to any previously known form have been found.
Dimensions:
Number of specimens: about 30
Holotype: 84:74.5
Paratypes: 88:79.7, 84:77.8,
Maximum: 93:95.1
Minimum: 84:74.5
Average: 88:81.5 (10 specimens)
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Emended description Sarjeant, 1984c
Cribroperidinium tenuitabulatum (Gerlach, 1961, p.159, pl.25, figs.10–11; text-figs.1–3) Helenes, 1984, p.124. Emendation: Sarjeant, 1984b, p.76, as Rhynchodiniopsis tenuitabulata. Holotype: Gerlach, 1961, pl.25, figs.10–11, lost according to Sarjeant (1984b, p.78. Lectotype: Sarjeant, 1984b, pl.2, fig.3, designated by Sarjeant (1984b, p.78) Taxonomic senior synonym: Gymnodinium (as and now Apteodinium) australiense, according to Fensome et al. (2016b, p.27). Originally Gonyaulax, subsequently Gonyaulacysta, thirdly Millioudodinium, fourthly (and subsequently) Cribroperidinium, fifthly RhynchodiniopsisAge: middle Oligocene–Middle Miocene.
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Original description Gerlach, 1961:
Holotype: Pr 1170/10 (269) Plate 25, Fig. 10 and 11
Paratypes: Pr1170/11 (283), Pr1170/12 (280)
Locus typicus: Bohrung Emsburen 7.
Stratum typicum: Mid-Oligocene
Derivation of the name: Reference to the poorly developed tabulation.
Remarks: The genus Gounyaulax has not yet been described as a representative of Tertiary sediments. This fact is surprising in itself, because these highly developed forms already occur among the first known dinoflagellates from the Middle Dogger and remain quite common in the Malmian and Cretaceous periods. They are also represented by many species in recent times. Thus, their occurrence in Tertiary strata of northwest Germany can close a gap.
Diagnosis:
Shell thin-walled, squat spheroidal, with a short, blunt apical horn. Tabulation scheme: 4', 6", 6"', 1p, 1ppl.
1'"'. Plates slanted by low, narrow ridges. Girdle furrow spiral with a displacement of approximately 1.5 furrow widths.
Membrane finely granulated.
Description:
The epitheca appears hemispherical in outline. A short, relatively broad horn protrudes at the apex, which tapers distally and is composed of four raised apical plates. Only a few specimens reveal the tabulation in detail. In order to define it clearly, the epitheca and hypotheca of various shells had to be examined. Of the apical plates, the 1' lies in the extension of the longitudinal furrow.
It is bordered laterally by the squat, trapezoidal 4'.
In the apical region of the dorsal side lie the two smaller apical plates 2' and 3'. Their outline is roughly triangular. The trapezoidal plates 2'', 3'', and 4" form the dorsal whorl, while the trapezoidal plates 1", 5", and 6" lie ventrally. The precingulates mentioned are relatively large, except for the 6", which is reduced to one-third of the other plates. Quite often, a trapezoidal pyloma is found in place of the 3".
The spiral girdle groove divides the theca into two almost equal parts. It is probably composed of six plates, which, like the others, are bordered by low, narrow hyaline ridges.
Ventrally, the ends of the girdle groove are offset by approximately 1.5 groove widths. The outer shell is slightly notched laterally in the region of the girdle groove. The longitudinal groove shows a clear division into two plates, as can be observed in most fossil Gonyaulax species. A polygonal lower plate (ppl) is separated from the relatively narrow longitudinal groove, bordered by curved sides. The almost hemispherical hypogeum consists of six postcingulates, one accessory plate (1p), and a large polygonal antapical plate. Characteristic of many Gonyaulax species is the ventrally located, strongly reduced, approximately elongated-polygonal 1"'. The elongated 1p is inserted into the acute angle it forms with the trapezoidal 2"', toward the antapex. Between 1"', 1p, and 3"' lies the 2'", which is also still fully developed, while the large, trapezoidal 3'", 4"", and 5'" form the dorsal whorl. The 6'' is located ventrally and is somewhat reduced in size. The antapex is composed of a large, polygonal and convex antapical plate.
The membrane of theca is finely granulated, very delicate, and brownish-yellow in color. The suture ridges appear somewhat lighter.
Affinities:
The present Gonyaulax species represents one of the relatively unornamented types of this genus, in which the sutures are only covered with narrow, entire ridges and not with branched protuberances or serrated crests. No analogies to any previously known form have been found.
Dimensions:
Number of specimens: about 30
Holotype: 84:74.5
Paratypes: 88:79.7, 84:77.8,
Maximum: 93:95.1
Minimum: 84:74.5
Average: 88:81.5 (10 specimens)
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Emended description Sarjeant, 1984c