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Circulodinium vermiculatum
Circulodinium vermiculatum, Stover and Helby, 1987
Holotype: Stover and Helby, 1987c, figs.4C-D; Fensome et al., 1996, figs.2-3 - p.2427.
Locus typicus: Exmouth Plateau, W Australia
Stratum typicum: Late Hauterivian-Barremian
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Original description: [Stover and Helby, 1987, p. 230]:
Description:
Cysts proximate and lenticular, with outline in dorsal view subcircular, an occasional specimen having a slight bulge on the left side of the antapical margin (Fig.4I,J).
Autophragm 2.5-4 µm thick, and unevenly thick on individual specimens. Ornamentation vermiculate, very irregular, thinner (incised) parts generally comprising less of the surface area (Fig.4E,G,L). However, because the vermiculation varies considerably, the reverse may be true, at least locally.
Archeopyle apical, type [tA], with a zigzag principal suture and a parasulcal notch usually offset (Fig.4A,D,J). Accessory archeopyle sutures short where present. Operculum usually free, infrequently adherent, constituent paraplates not differentiated.
Paratabulation indicated almost exclusively by the archeopyle margin along the anterior borders of the six precingular paraplates. No expression of a paracingulum observed. On occasional specimens, a midventral, somewhat less sculptured, depression on the hypocyst interpreted as representing the posterior part of the parasulcus (Fig.4C,E,l,J,).
Parasulcus usually indicated only by the sulcal notch.
Dimensions:
Specimens 110-140 µm in width, 95-130 µm (without opercula) and 128-142 µm (with opercula) in length, 12 specimens measured.
Affinities:
The vermiculate ornamentation characterizes C. vermiculatum and distinguishes it within the genus. Of species attributed to Circulodinium by Helby (1987), C. colliveri (Cookson & Eisenack 1960) is granular, C. asperum (Singh 1971) and C. hirtellum Alberti 1961 are sparsely spinate, and C. attadalicum (Cookson & Eisenack 1962) and C. deflandrei Alberti 1961 are densely spinate.
Holotype: Stover and Helby, 1987c, figs.4C-D; Fensome et al., 1996, figs.2-3 - p.2427.
Locus typicus: Exmouth Plateau, W Australia
Stratum typicum: Late Hauterivian-Barremian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Stover and Helby, 1987, p. 230]:
Description:
Cysts proximate and lenticular, with outline in dorsal view subcircular, an occasional specimen having a slight bulge on the left side of the antapical margin (Fig.4I,J).
Autophragm 2.5-4 µm thick, and unevenly thick on individual specimens. Ornamentation vermiculate, very irregular, thinner (incised) parts generally comprising less of the surface area (Fig.4E,G,L). However, because the vermiculation varies considerably, the reverse may be true, at least locally.
Archeopyle apical, type [tA], with a zigzag principal suture and a parasulcal notch usually offset (Fig.4A,D,J). Accessory archeopyle sutures short where present. Operculum usually free, infrequently adherent, constituent paraplates not differentiated.
Paratabulation indicated almost exclusively by the archeopyle margin along the anterior borders of the six precingular paraplates. No expression of a paracingulum observed. On occasional specimens, a midventral, somewhat less sculptured, depression on the hypocyst interpreted as representing the posterior part of the parasulcus (Fig.4C,E,l,J,).
Parasulcus usually indicated only by the sulcal notch.
Dimensions:
Specimens 110-140 µm in width, 95-130 µm (without opercula) and 128-142 µm (with opercula) in length, 12 specimens measured.
Affinities:
The vermiculate ornamentation characterizes C. vermiculatum and distinguishes it within the genus. Of species attributed to Circulodinium by Helby (1987), C. colliveri (Cookson & Eisenack 1960) is granular, C. asperum (Singh 1971) and C. hirtellum Alberti 1961 are sparsely spinate, and C. attadalicum (Cookson & Eisenack 1962) and C. deflandrei Alberti 1961 are densely spinate.