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Circulodinium formosum
Circulodinium formosum, Iosifova, 1992
Holotype: Iosifova, pl. IX, 3, Fig. 1; Iosifova 1996: Plate XVI, 6a,b; Fig. 5
Locus typicus: Chernaya Retchka outcrop, the Ryazan district, Russia.
Stratum typicum: Valanginian (Note: Iosifova 1996: deposits of probable Hauterivian age)
Distribution: Valanginian of Moscow syneclise.
Occurrence: Tchernaya Retchka outcrop, deposits of probable Hauterivian age.
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Original description: [Iosifova, 1992, p. 75]:
Description:
(fig.1c, d). Cyst is proximate, subspherical, dorsoventrally flattened. Two (one) small antapical horns are sometimes present. Wall is bilaminar; autophragm and periphragm are very close together.
Periphragm forms processes, which are developed only on periphery of cyst. Middle parts of ventral and dorsal sides are free of such processes. Closer toward center, processes decrease greatly in size. Processes are continuous, closed, buccinate, oblate, more rarely digitate, cylindrical of bifucate, and comprise about 1/5 width of cyst. Some processes joined in twos and threes at proximal or distal ends of membrane. Bases of processes are often perforated.
Archeopyle is apical, tA, with zig-zag margin. There are no signs of paratabulation apart from structure of archeopyle.
Dimensions in microns (without apex):
Spec. No.LWD
Holotype (4831/4196-1)99.894.119.2
4831/4196-2-17382.517.3
4831/4196-2-280.680.621.1
4831/4196-3-376.880.615.3
Affinities:
Differs from C. distinctum (Deflandre et Cookson) Jansonius in perforate bases of processes and also in that some processes may be linked together at distal or proximal ends of membrane.
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Supplemental description:
Iosifova 1996, p. 211, 213, 215
Diagnosis:
Cyst proximate, subcircular, dorsoventrally compressed. One (two) small antapical lobes occasionally present.
Periphragm forms the processes, distributed only on the marginal parts of the cyst. Processes are solid, digitate, cylindrical or bifurcate. Some processes are connected proximally by the low ridges. The bases of the processes are perforated.
Paratabulation indicated only by archeopyle suture.
Archeopyle apical, Type [tA], with zig-zag margin.
Description:
Cysts proximate, subcircular, dorsoventrally compressed. One (or two) small antapical lobes occasionally present.
Cyst wall two-layered, periphragm and endophragm are in contact everywhere. Periphragm forms the processes, distributed only on the marginal parts of the cyst. Mid-ventral and mid-dorsal parts of the cyst lack processes. The length of the processes decreases towards the center of the cyst. Processes are solid, digitate, cylindrical or bifurcate, in length about a fifth of the width of the cyst. Some processes are connected proximally by the low ridges. The bases of the processes are perforated. The perforation varies greatly. Frequently most of the processes on a given specimen are perforated, although some specimens have only a few perforated processes. When the perforation is strong, it expands onto the central body near the base of the processes. The wide processes frequently are fibrous, especially at the proximal ends. the complex processes on the antapex was found only on the holotype.
Archeopyle apical, Type [tA], with zig-zag margin.
Dimensions:
Length (without apex): holotype: 100 µm, range: 73-100 µm; width: holotype: 94 µm, range: 81-94 µm; length of the processes (max): holotype: 19 µm, range: 15-21 µm. Six specimens measured.
Affinities: This species resembles C. distinctum (Deflandre and Cookson, 1955) Jansonius, 1986, especially C. distinctum subsp. Iongispinatum Davey, 1978. but differs from it by the perforation of the bases of its processes. It is possible, that this taxon is a subspecies of C. distinctum, because of the presence of intermediate forms.
Holotype: Iosifova, pl. IX, 3, Fig. 1; Iosifova 1996: Plate XVI, 6a,b; Fig. 5
Locus typicus: Chernaya Retchka outcrop, the Ryazan district, Russia.
Stratum typicum: Valanginian (Note: Iosifova 1996: deposits of probable Hauterivian age)
Distribution: Valanginian of Moscow syneclise.
Occurrence: Tchernaya Retchka outcrop, deposits of probable Hauterivian age.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Iosifova, 1992, p. 75]:
Description:
(fig.1c, d). Cyst is proximate, subspherical, dorsoventrally flattened. Two (one) small antapical horns are sometimes present. Wall is bilaminar; autophragm and periphragm are very close together.
Periphragm forms processes, which are developed only on periphery of cyst. Middle parts of ventral and dorsal sides are free of such processes. Closer toward center, processes decrease greatly in size. Processes are continuous, closed, buccinate, oblate, more rarely digitate, cylindrical of bifucate, and comprise about 1/5 width of cyst. Some processes joined in twos and threes at proximal or distal ends of membrane. Bases of processes are often perforated.
Archeopyle is apical, tA, with zig-zag margin. There are no signs of paratabulation apart from structure of archeopyle.
Dimensions in microns (without apex):
Spec. No.LWD
Holotype (4831/4196-1)99.894.119.2
4831/4196-2-17382.517.3
4831/4196-2-280.680.621.1
4831/4196-3-376.880.615.3
Affinities:
Differs from C. distinctum (Deflandre et Cookson) Jansonius in perforate bases of processes and also in that some processes may be linked together at distal or proximal ends of membrane.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Supplemental description:
Iosifova 1996, p. 211, 213, 215
Diagnosis:
Cyst proximate, subcircular, dorsoventrally compressed. One (two) small antapical lobes occasionally present.
Periphragm forms the processes, distributed only on the marginal parts of the cyst. Processes are solid, digitate, cylindrical or bifurcate. Some processes are connected proximally by the low ridges. The bases of the processes are perforated.
Paratabulation indicated only by archeopyle suture.
Archeopyle apical, Type [tA], with zig-zag margin.
Description:
Cysts proximate, subcircular, dorsoventrally compressed. One (or two) small antapical lobes occasionally present.
Cyst wall two-layered, periphragm and endophragm are in contact everywhere. Periphragm forms the processes, distributed only on the marginal parts of the cyst. Mid-ventral and mid-dorsal parts of the cyst lack processes. The length of the processes decreases towards the center of the cyst. Processes are solid, digitate, cylindrical or bifurcate, in length about a fifth of the width of the cyst. Some processes are connected proximally by the low ridges. The bases of the processes are perforated. The perforation varies greatly. Frequently most of the processes on a given specimen are perforated, although some specimens have only a few perforated processes. When the perforation is strong, it expands onto the central body near the base of the processes. The wide processes frequently are fibrous, especially at the proximal ends. the complex processes on the antapex was found only on the holotype.
Archeopyle apical, Type [tA], with zig-zag margin.
Dimensions:
Length (without apex): holotype: 100 µm, range: 73-100 µm; width: holotype: 94 µm, range: 81-94 µm; length of the processes (max): holotype: 19 µm, range: 15-21 µm. Six specimens measured.
Affinities: This species resembles C. distinctum (Deflandre and Cookson, 1955) Jansonius, 1986, especially C. distinctum subsp. Iongispinatum Davey, 1978. but differs from it by the perforation of the bases of its processes. It is possible, that this taxon is a subspecies of C. distinctum, because of the presence of intermediate forms.