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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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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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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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