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Cerebrocysta poulsenii
Cerebrocysta poulsenii, de Verteuil and Norris, 1996
Holotype: Plate 12, figs. 9-14
Locus typicus: BG&E Site North Section, Chesapeake Bay, Calvert County, Maryland.
Stratum typicum: Upper middle Miocene Conoy Member of the Choptank Formation
Occurrence: Lower through upper Miocene in the Salisbury Embayment (DN3 - DN8).
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Original description as Cerebrocysta poulsenii: [de Verteuil and Norris, 1996, p. 148-150]:
Diagnosis:
Small ovoidal cyst characterized by a thin, evenly granulate autoblast with discontinuous, even septa that suggest but do not delimit tabulation. The archeopyle is simple Type P.
Description:
Cysts small, ovoidal and proximate to marginally proximochorate.
The wall is simple, comprising thin homogeneous pedium, granulate prismatic luxuriae and septate proximate luxuriae. Pedium is ca. 0.2 µm thick and supports very densely packed pila, 1.0-1.3 µm long, without a tegillum. The wall surface is finely and evenly granulate with granules up to 0.4 µm wide. Total wall thickness excluding septa is up to 1.5 µm. The scabrate septa are solid, uniformly 0.5 to 1.0 µm thick and only slightly wider at the base; they appear to be fused with the pedium directly without intermediary pila. Some alveoles 0.2 to 0.5 µm across may be internally present at the bases of septa but pericoels are not developed.
The septa themselves are quite variable in length and density with respect to spacing. Some specimens have essentially non-tabular, short septa, 3.0 to 8.0 µm long, that are straight, or have one bend and show little connectivity. Others have longer septa with several bends and greater connectivity forming fence-like patterns. These patterns do not delimit tabulation but are suggestive of it in that the septa are more complex and closely spaced in areas where smaller fields converge as at the apex and sulcus; the cingulum is incompletely delimited by linear septa. The septa have straight tops and terminate abruptly but their height among specimens is variable, from 1.0 to 4.0 µm; on individual specimens the height is relatively constant. The mid-dorsal precingular archeopyle is quite large and suggestive of standard gonyaulacalean 3"; its geometry is theta-form to slightly deltaform and iso-planate, or camerate if the anterior margin is weakly geniculate. There are often two small notches ca. 1.5 µm deep on the posterior margin of the archeopyle, each ca. 3 or 4 µm in from the two basal corners.
The archeopyle margin is even or uneven and its angles may be rounded or sharp.
There are no depressions on the cyst to indicate cingulum or sulcus and no apical pore structure.
Dimensions:
Length, excluding processes, 25(34)41 µm; holotype 37 µm. Width, excluding septa, 24(26.1)28 µm; holotype 27 µm. Eleven specimens measured.
Remarks:
Cerebrocysta poulsenii is never common in the shallow to marginal marine deposits of the Choptank and Saint Marys formations in their type areas. This species seems to have an outer neritic environmental preference. The lowest and highest occurrences of Cerebrocysta poulsenii are useful biostratigraphic horizons.
Affinities/Comparison:
As a result of its discontinuous, nontabular septa Cerebrocysta poulsenii is a very distinctive species. Only when the septa are poorly developed, as isolated blade-like structures, is it possible to confuse Cerebrocysta poulsenii with species such as Operculodinium piaseckii and Operculodinim janduchenei. Similarly, Cerebrocysta poulsenii is quite unlike Cerebrocysta satchelliae and other species of this genus discussed below in that is has narrow, relatively high septa, rather than low ridges; also, the archeopyle is monoplacoid.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Cerebrocysta poulsenii de Verteuil and Norris, 1996. According to de Verteuil and Norris (1996, p.149), this is a small ovoidal cyst characterized by a thin, evenly granulate autoblast with discontinuous, even septa that suggest but do not delimit tabulation. The archeopyle is simple Type P. Pedium supports densely packed pila, ca 1-1.3 µm long, without a tegillum. Wall thickness excluding septa is about 1.5 µm. The scabrate septa are solid, uniformly 0.5 to 1.0 µm thick and may be straight or form several curves. Cingulum incompletely delimited. Height of septa is 1 to 4 µm. Size: length excluding processes 25-41 µm, width, excluding septa 24-28 µm.
Holotype: Plate 12, figs. 9-14
Locus typicus: BG&E Site North Section, Chesapeake Bay, Calvert County, Maryland.
Stratum typicum: Upper middle Miocene Conoy Member of the Choptank Formation
Occurrence: Lower through upper Miocene in the Salisbury Embayment (DN3 - DN8).
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Cerebrocysta poulsenii: [de Verteuil and Norris, 1996, p. 148-150]:
Diagnosis:
Small ovoidal cyst characterized by a thin, evenly granulate autoblast with discontinuous, even septa that suggest but do not delimit tabulation. The archeopyle is simple Type P.
Description:
Cysts small, ovoidal and proximate to marginally proximochorate.
The wall is simple, comprising thin homogeneous pedium, granulate prismatic luxuriae and septate proximate luxuriae. Pedium is ca. 0.2 µm thick and supports very densely packed pila, 1.0-1.3 µm long, without a tegillum. The wall surface is finely and evenly granulate with granules up to 0.4 µm wide. Total wall thickness excluding septa is up to 1.5 µm. The scabrate septa are solid, uniformly 0.5 to 1.0 µm thick and only slightly wider at the base; they appear to be fused with the pedium directly without intermediary pila. Some alveoles 0.2 to 0.5 µm across may be internally present at the bases of septa but pericoels are not developed.
The septa themselves are quite variable in length and density with respect to spacing. Some specimens have essentially non-tabular, short septa, 3.0 to 8.0 µm long, that are straight, or have one bend and show little connectivity. Others have longer septa with several bends and greater connectivity forming fence-like patterns. These patterns do not delimit tabulation but are suggestive of it in that the septa are more complex and closely spaced in areas where smaller fields converge as at the apex and sulcus; the cingulum is incompletely delimited by linear septa. The septa have straight tops and terminate abruptly but their height among specimens is variable, from 1.0 to 4.0 µm; on individual specimens the height is relatively constant. The mid-dorsal precingular archeopyle is quite large and suggestive of standard gonyaulacalean 3"; its geometry is theta-form to slightly deltaform and iso-planate, or camerate if the anterior margin is weakly geniculate. There are often two small notches ca. 1.5 µm deep on the posterior margin of the archeopyle, each ca. 3 or 4 µm in from the two basal corners.
The archeopyle margin is even or uneven and its angles may be rounded or sharp.
There are no depressions on the cyst to indicate cingulum or sulcus and no apical pore structure.
Dimensions:
Length, excluding processes, 25(34)41 µm; holotype 37 µm. Width, excluding septa, 24(26.1)28 µm; holotype 27 µm. Eleven specimens measured.
Remarks:
Cerebrocysta poulsenii is never common in the shallow to marginal marine deposits of the Choptank and Saint Marys formations in their type areas. This species seems to have an outer neritic environmental preference. The lowest and highest occurrences of Cerebrocysta poulsenii are useful biostratigraphic horizons.
Affinities/Comparison:
As a result of its discontinuous, nontabular septa Cerebrocysta poulsenii is a very distinctive species. Only when the septa are poorly developed, as isolated blade-like structures, is it possible to confuse Cerebrocysta poulsenii with species such as Operculodinium piaseckii and Operculodinim janduchenei. Similarly, Cerebrocysta poulsenii is quite unlike Cerebrocysta satchelliae and other species of this genus discussed below in that is has narrow, relatively high septa, rather than low ridges; also, the archeopyle is monoplacoid.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Cerebrocysta poulsenii de Verteuil and Norris, 1996. According to de Verteuil and Norris (1996, p.149), this is a small ovoidal cyst characterized by a thin, evenly granulate autoblast with discontinuous, even septa that suggest but do not delimit tabulation. The archeopyle is simple Type P. Pedium supports densely packed pila, ca 1-1.3 µm long, without a tegillum. Wall thickness excluding septa is about 1.5 µm. The scabrate septa are solid, uniformly 0.5 to 1.0 µm thick and may be straight or form several curves. Cingulum incompletely delimited. Height of septa is 1 to 4 µm. Size: length excluding processes 25-41 µm, width, excluding septa 24-28 µm.