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Cerebrocysta irregularis
Cerebrocysta irregularis, Schreck et al., 2012, p.90–91, pl.3, figs.11–20.
Holotype: Schreck et al., 2012, pl.3, figs.11–14.
Stratigraphic occurrence: from the uppermost Langhian (13.8 Ma) to lower Tortonian (10.4 Ma); Tectatodinium sp. 4 of Manum et al. (1989), which we questionably synonymise with Corrudinium irregulare, ranges from uppermost Langhian through mid-Tortonian in the Norwegian Sea.
Age: latest Langhian–early Tortonian.
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Original description: [Schreck et al., 2012]:
Diagnosis:
A species of Cerebrocysta having an almost spherical, ovoidal shape; and surface ornamented with sinuous and discontinuous muri of irregular width (up to c. 1.5 μm) that form a surface pattern varying from microrugulate to an incomplete and irregular microreticulation; with spacing between muri up to c. 2.0 to 3.0 μm.
The archeopyle, formed by loss of plate 3″, has well-defined angles.
Description:
Proximate cyst with ovoidal shape that is close to spherical, occasionally with a low apical protuberance. Wall ornament consists of sinuous, discontinuous muri that form a surface pattern varying from microrugulate to an incomplete and irregular microreticulation. The muri are of irregular width that varies between c. 1.5 μm and b0.2 μm, this variation occurring on the same cyst. Muri often widen at intersections. Muri are up to about 1.5 μm high; but height varies, with narrower muri often lower than wider muri. Crests are flat-topped (especially at intersections) or taper distally. The lacunae between muri are usually up to about 2.0 μm diameter (on the holotype mostly 1.5 μm or less; occasionally reaching 3.0 μm in other specimens), and vary from rounded polygonal to rectangular. The underlying pedium is about 0.2–0.3 μm thick, and both pedium and overlying muri appear solid and continuous under light microscopy.
The ornament covers the entire surface of the cyst without variation, and extends to the archeopyle margins without modification.
The archeopyle is formed by loss of plate 3″, and has well-defined angles.
There is no other expression of tabulation.
Affinities/Discussion:
The holotype has a slight (0.5 μm) apical protuberance, and one specimen was found to have an unusually pronounced apical protuberance (Plate III, 16), a feature that is absent or very weakly developed in other specimens. Tectatodinium sp. 4 of Manum et al. (1989), from the Miocene of the Norwegian Sea, is questionably synonymized with Cerebrocysta irregulare on account of its similar ornament but more pronounced apical protuberance. Cerebrocysta irregulare differs from all other validly described species of the genera Cerebrocysta, Corrudinium and Pyxidinopsis by its relatively small size and irregularly-shaped muri that form an incomplete and irregular microreticulate to microrugulate pattern. “Cerebrocysta cassinascoensis” Zevenboom and Santarelli in Zevenboom, 1995 (unpublished manuscript name), from the Langhian through base Serravallian of Italy, is very similar to C. irregulare but differs in having a coarser microreticulation, and apparently larger overall size range of 40–50 μm (Zevenboom and Santarelli in Zevenboom, 1995), although the illustrations of this species somewhat contradict its description. Specimens reported rarely from the upper Langhian of Hungary as Cerebrocysta cassinascoensis” Zevenboom and Santarelli in Zevenboom, 1995 by Jiménez-Moreno et al. (2006) have slightly coarser ornament than C. irregulare but are of similar size (maximum diameter 37–39 μm based on three specimens; M.J.H., unpubl. data). Further research on these Mediterranean–Paratethyan morphotypes is needed to assess their relationship fully with C. irregulare.
Dimensions:
Holotype: length (including ornament), 39 μm; wall thickness, c. 1.4 μm.
Range: maximum diameter (including ornament), 32 (38.4) 42 μm; wall thickness, c. 0.9–1.8 μm. Eighteen specimens measured.
Holotype: Schreck et al., 2012, pl.3, figs.11–14.
Stratigraphic occurrence: from the uppermost Langhian (13.8 Ma) to lower Tortonian (10.4 Ma); Tectatodinium sp. 4 of Manum et al. (1989), which we questionably synonymise with Corrudinium irregulare, ranges from uppermost Langhian through mid-Tortonian in the Norwegian Sea.
Age: latest Langhian–early Tortonian.
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Original description: [Schreck et al., 2012]:
Diagnosis:
A species of Cerebrocysta having an almost spherical, ovoidal shape; and surface ornamented with sinuous and discontinuous muri of irregular width (up to c. 1.5 μm) that form a surface pattern varying from microrugulate to an incomplete and irregular microreticulation; with spacing between muri up to c. 2.0 to 3.0 μm.
The archeopyle, formed by loss of plate 3″, has well-defined angles.
Description:
Proximate cyst with ovoidal shape that is close to spherical, occasionally with a low apical protuberance. Wall ornament consists of sinuous, discontinuous muri that form a surface pattern varying from microrugulate to an incomplete and irregular microreticulation. The muri are of irregular width that varies between c. 1.5 μm and b0.2 μm, this variation occurring on the same cyst. Muri often widen at intersections. Muri are up to about 1.5 μm high; but height varies, with narrower muri often lower than wider muri. Crests are flat-topped (especially at intersections) or taper distally. The lacunae between muri are usually up to about 2.0 μm diameter (on the holotype mostly 1.5 μm or less; occasionally reaching 3.0 μm in other specimens), and vary from rounded polygonal to rectangular. The underlying pedium is about 0.2–0.3 μm thick, and both pedium and overlying muri appear solid and continuous under light microscopy.
The ornament covers the entire surface of the cyst without variation, and extends to the archeopyle margins without modification.
The archeopyle is formed by loss of plate 3″, and has well-defined angles.
There is no other expression of tabulation.
Affinities/Discussion:
The holotype has a slight (0.5 μm) apical protuberance, and one specimen was found to have an unusually pronounced apical protuberance (Plate III, 16), a feature that is absent or very weakly developed in other specimens. Tectatodinium sp. 4 of Manum et al. (1989), from the Miocene of the Norwegian Sea, is questionably synonymized with Cerebrocysta irregulare on account of its similar ornament but more pronounced apical protuberance. Cerebrocysta irregulare differs from all other validly described species of the genera Cerebrocysta, Corrudinium and Pyxidinopsis by its relatively small size and irregularly-shaped muri that form an incomplete and irregular microreticulate to microrugulate pattern. “Cerebrocysta cassinascoensis” Zevenboom and Santarelli in Zevenboom, 1995 (unpublished manuscript name), from the Langhian through base Serravallian of Italy, is very similar to C. irregulare but differs in having a coarser microreticulation, and apparently larger overall size range of 40–50 μm (Zevenboom and Santarelli in Zevenboom, 1995), although the illustrations of this species somewhat contradict its description. Specimens reported rarely from the upper Langhian of Hungary as Cerebrocysta cassinascoensis” Zevenboom and Santarelli in Zevenboom, 1995 by Jiménez-Moreno et al. (2006) have slightly coarser ornament than C. irregulare but are of similar size (maximum diameter 37–39 μm based on three specimens; M.J.H., unpubl. data). Further research on these Mediterranean–Paratethyan morphotypes is needed to assess their relationship fully with C. irregulare.
Dimensions:
Holotype: length (including ornament), 39 μm; wall thickness, c. 1.4 μm.
Range: maximum diameter (including ornament), 32 (38.4) 42 μm; wall thickness, c. 0.9–1.8 μm. Eighteen specimens measured.