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Gonyaulacysta circumfoveolata
Gonyaulacysta circumfoveolata Prössl, 1990, p.103, pl.10, figs.6-10 ex Prössl, 1992b, p.113-115.
Holotype: Prössl, 1990, pl.10, figs.8-10. This name was not validly published in Prössl (1990, p.103), since that author did not specify the lodgment of the holotype. Questionable assignment: Prössl (1990, p.103). Age: Late Aptian
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Original description Gonyaulacysta circumfoveolata (Prossl, 1990)
Derivatio nominis: circum 一um, around; because of the foveolate paraplates of the endocyst.
Holotype: 101-91-1.
Paratype: 101-91-2.
Typical locus and typical stratum: Konrad 101 borehole, depth 473.89 m. Upper Apt (High Gargas).
Stratigraphic range: Upper Apt, PNR 91-88.
Diagnosis: Cavate cyst with a thin periphragm and a thick endophrammy. The periphragm exhibits paratabular folds or sutures. The larger paraplates of the endocyst are foveolate, and their sculpture is interrupted by a smooth "ring."
Description: The periphragm is smooth and has a short, truncated horn at the apex. The paratabulation is represented by sutures or folds and, especially at the antapex, by septa. On the endocyst, part of the paratabulation is characterized by the lack of ornamentation along the parasutures. The intratabular ornamentation of the larger plates is interrupted by a subcircular, ornament-free zone. Foveolae may also occur on the paraplate, the largest of which are usually concentrated in the center. The paratabulation appears to correspond to the following pattern: 4', 6", Xe, 6"', 1 p, 1"". The archaeopyle corresponds to plate 3" (type P).
Remarks: The thin periphragm of the cyst is usually so severely destroyed that only the endocyst remains. Of the entire sample, only the holotype with a fully preserved apical horn was found.
Dimensions: Holotype 101-91-1.
Paratype 101-91-2.
Endocyst: 50 x 43 μm.
Endocyst: 50 x 43 μm.
Epicyst: 65 x 49 μm,
Apical horn: 10 μm.
Description: Heilmann-Clausen 1995, p. 295-297
Suturocavate cyst with prominent equatorial pericoel. A hollow apical horn is formed by the periphragm. The parasutures are marked by ledges of variable height (1-7 llm). The distal margins of the ledges are faintly denticulate, or almost smooth.
A distinct ornament of rounded, different-sized holes is present. Most of the holes are situated in the periphragm. In some specimens the holes may be so closely placed that the periphragm is better characterized as a reticulum. In other specimens the holes are more widely separated. A few very large holes (up to 4 llm in diameter) occurs in the central areasof paraplates, where the phragma are in close contact. Sometimes these large holes look very much like openings in the periphragm. In other cases they appear to be vacuoles in a foamy layer between the endo- and periphragm. A precingular archaeopyle (type P) is present.
Dimensions: Total length of cyst: 49-59 µm. Total breadth of cyst: 49µm (2 specimens measured).
Discussion: Heilmann-Clausen 1995, p. 295-297
The present interpretation of the ornament differs a little from that of PROSSL (1990). However, there is no doubt that this distinct species is the same as G.? circumfoveolata. The present author agrees that the generic assignment is uncertain. There is affinity to the genera Stephodinium and Endoscrinium, but the former typically
Barremian-Aptian Dinoflagellates and Calcareous Nannofossils in the Ahlum 1 borehole lacks an apical horn and the latter is typically circumcavate. The genus Spongodinium has a foamy layer between the phragma, but differs in a number of more principal characters such as paraplate configuration and in the presence of accessory parasutures.
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Holotype: Prössl, 1990, pl.10, figs.8-10. This name was not validly published in Prössl (1990, p.103), since that author did not specify the lodgment of the holotype. Questionable assignment: Prössl (1990, p.103). Age: Late Aptian
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Original description Gonyaulacysta circumfoveolata (Prossl, 1990)
Derivatio nominis: circum 一um, around; because of the foveolate paraplates of the endocyst.
Holotype: 101-91-1.
Paratype: 101-91-2.
Typical locus and typical stratum: Konrad 101 borehole, depth 473.89 m. Upper Apt (High Gargas).
Stratigraphic range: Upper Apt, PNR 91-88.
Diagnosis: Cavate cyst with a thin periphragm and a thick endophrammy. The periphragm exhibits paratabular folds or sutures. The larger paraplates of the endocyst are foveolate, and their sculpture is interrupted by a smooth "ring."
Description: The periphragm is smooth and has a short, truncated horn at the apex. The paratabulation is represented by sutures or folds and, especially at the antapex, by septa. On the endocyst, part of the paratabulation is characterized by the lack of ornamentation along the parasutures. The intratabular ornamentation of the larger plates is interrupted by a subcircular, ornament-free zone. Foveolae may also occur on the paraplate, the largest of which are usually concentrated in the center. The paratabulation appears to correspond to the following pattern: 4', 6", Xe, 6"', 1 p, 1"". The archaeopyle corresponds to plate 3" (type P).
Remarks: The thin periphragm of the cyst is usually so severely destroyed that only the endocyst remains. Of the entire sample, only the holotype with a fully preserved apical horn was found.
Dimensions: Holotype 101-91-1.
Paratype 101-91-2.
Endocyst: 50 x 43 μm.
Endocyst: 50 x 43 μm.
Epicyst: 65 x 49 μm,
Apical horn: 10 μm.
Description: Heilmann-Clausen 1995, p. 295-297
Suturocavate cyst with prominent equatorial pericoel. A hollow apical horn is formed by the periphragm. The parasutures are marked by ledges of variable height (1-7 llm). The distal margins of the ledges are faintly denticulate, or almost smooth.
A distinct ornament of rounded, different-sized holes is present. Most of the holes are situated in the periphragm. In some specimens the holes may be so closely placed that the periphragm is better characterized as a reticulum. In other specimens the holes are more widely separated. A few very large holes (up to 4 llm in diameter) occurs in the central areasof paraplates, where the phragma are in close contact. Sometimes these large holes look very much like openings in the periphragm. In other cases they appear to be vacuoles in a foamy layer between the endo- and periphragm. A precingular archaeopyle (type P) is present.
Dimensions: Total length of cyst: 49-59 µm. Total breadth of cyst: 49µm (2 specimens measured).
Discussion: Heilmann-Clausen 1995, p. 295-297
The present interpretation of the ornament differs a little from that of PROSSL (1990). However, there is no doubt that this distinct species is the same as G.? circumfoveolata. The present author agrees that the generic assignment is uncertain. There is affinity to the genera Stephodinium and Endoscrinium, but the former typically
Barremian-Aptian Dinoflagellates and Calcareous Nannofossils in the Ahlum 1 borehole lacks an apical horn and the latter is typically circumcavate. The genus Spongodinium has a foamy layer between the phragma, but differs in a number of more principal characters such as paraplate configuration and in the presence of accessory parasutures.
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