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Cerebrocysta namocensis
Cerebrocysta? namocensis, Head et al., 1989
Head et al., 1989, questionably included this species in Cerebrocysta.
Holotype: Head et al., 1989, pl.3, figs.10-11
Locus typicus: ODP leg 105, site 646, Labrador Sea
Stratum typicum: Late Miocene
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Original description: [Head et al., 1989, p. 454]:
Diagnosis:
Cysts autophragmal, spherical, proximate, with smooth surface and a network of low sinuous ridges forming a fine reticulate pattern. Ridges apparently do not reflect paratabulation except at the apex, where they may form a small circular to subpolygonal ring.
Archeopyle Type 2P; operculum free, probably compound.
Description:
Uncompressed cysts are spherical but may be folded into a broadly elliptical outline. Ridges are about 0.5-1.0 µm high, rounded in transverse section and variably sinuous in plan view. Lacunae are irregularly polygonal and range from about 0.5 to about 3.0 µm in maximum diameter. A variably pronounced apical ring structure of slightly thicker ridges was observed in four specimens, including the holotype. The ring is subcircular to subpolygonal, of about 4.5-5.5 µm in diameter (based on five specimens); and encloses a small number of slightly thinner sinuous ridges. In two specimens there was observed within this apical ring, a concentric inner ring enclosing a central lacuna (reflecting an apical pore?) having a diameter of 1.5 µm.
Archeopyle is precingular Type 2P (recognized in all specimens found), and possibly Type 2P (3""-4"") assuming a gonyaulacacean paratabulation and based on provisional interpretation of archeopyle shape in three specimens. Accessory sutures were not observed. Separated and detached opercular paraplates found within two cysts indicate a compound operculum.
Dimensions:
Holotype: diameter, 46 µm.
Range in diameter, 36(43.7)51 µm. Wall thickness (including ridges), up to about 2 µm. Eighteen specimens were measured.
Remarks:
Many of the specimens recorded had undergone some degree of folding, and the apical ring structure observed in five specimens may have been obscured from view in other specimens. This structure possibly reflects the apical pore and/or preapical plate series of the thecate stage.
Affinities:
The genus Cerebrocysta was erected for species with "an apparently random ornament of low crests" (Bujak, in Bujak et al., 1980, p. 42) whereas in C.? namocensis, the ornament is more completely reticulated, for which reason it is provisionally assigned to this genus. Pyxidinopsis Habib, 1976 includes autophragmal species with low reticulate ornament, but this genus only accommodates species with a simple precingular archeopyle, compared to the Type 2P archeopyle of C.? namocensis. Muraticysta has radiating, thin, delicate, nontabular Imuri, which arise from a reticulate base (this chapter), compared to the low ridges of C.? namocensis.
Head et al., 1989, questionably included this species in Cerebrocysta.
Holotype: Head et al., 1989, pl.3, figs.10-11
Locus typicus: ODP leg 105, site 646, Labrador Sea
Stratum typicum: Late Miocene
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Head et al., 1989, p. 454]:
Diagnosis:
Cysts autophragmal, spherical, proximate, with smooth surface and a network of low sinuous ridges forming a fine reticulate pattern. Ridges apparently do not reflect paratabulation except at the apex, where they may form a small circular to subpolygonal ring.
Archeopyle Type 2P; operculum free, probably compound.
Description:
Uncompressed cysts are spherical but may be folded into a broadly elliptical outline. Ridges are about 0.5-1.0 µm high, rounded in transverse section and variably sinuous in plan view. Lacunae are irregularly polygonal and range from about 0.5 to about 3.0 µm in maximum diameter. A variably pronounced apical ring structure of slightly thicker ridges was observed in four specimens, including the holotype. The ring is subcircular to subpolygonal, of about 4.5-5.5 µm in diameter (based on five specimens); and encloses a small number of slightly thinner sinuous ridges. In two specimens there was observed within this apical ring, a concentric inner ring enclosing a central lacuna (reflecting an apical pore?) having a diameter of 1.5 µm.
Archeopyle is precingular Type 2P (recognized in all specimens found), and possibly Type 2P (3""-4"") assuming a gonyaulacacean paratabulation and based on provisional interpretation of archeopyle shape in three specimens. Accessory sutures were not observed. Separated and detached opercular paraplates found within two cysts indicate a compound operculum.
Dimensions:
Holotype: diameter, 46 µm.
Range in diameter, 36(43.7)51 µm. Wall thickness (including ridges), up to about 2 µm. Eighteen specimens were measured.
Remarks:
Many of the specimens recorded had undergone some degree of folding, and the apical ring structure observed in five specimens may have been obscured from view in other specimens. This structure possibly reflects the apical pore and/or preapical plate series of the thecate stage.
Affinities:
The genus Cerebrocysta was erected for species with "an apparently random ornament of low crests" (Bujak, in Bujak et al., 1980, p. 42) whereas in C.? namocensis, the ornament is more completely reticulated, for which reason it is provisionally assigned to this genus. Pyxidinopsis Habib, 1976 includes autophragmal species with low reticulate ornament, but this genus only accommodates species with a simple precingular archeopyle, compared to the Type 2P archeopyle of C.? namocensis. Muraticysta has radiating, thin, delicate, nontabular Imuri, which arise from a reticulate base (this chapter), compared to the low ridges of C.? namocensis.