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Phthanoperidinium zosimovichi
Phthanoperidinium zosimovichi Stotland in Andreeva-Grigorovich et al., 2011, p.39–40, pl.57, figs.1–9,2a,4a,9a; pl.58, figs.1a–d,2a–d,3a–d. Holotype: Andreeva-Grigorovich et al., 2011, pl.57, figs.1–9.2a,4a,9a. Age: early Oligocene.
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Original description: [Andreeva-Grigorovich et al., 2011] (translated from Russian):
Phthanoperidinium zosimovichi Stotland sp. nov. Tables LVII, 1-9; LVIII, 1-3
Name. In honor of Vladimir Yuryevich Zosimovich, a famous paleontologist and stratigrapher of the Cenozoic of Ukraine.
Diagnosis. Round-elliptical, acavate peridiniacean cyst, dorsoventrally weak-ly compressed, paratabulation expressed by short penitabular ridges and intrata-bular fine-grained-reticulate structures of plates and pandasutural zones. Apical horn is triangular-trapeziform, antapical horns very much reduced and invisible.
Description. An aquatic cyst with peridinioid paratabulation. The outline in the dorsoventral plane is rounded-elliptical. The "compression" coefficient is 0.6-0.7. The epicysta is equal in length to the hypocyst. The apical horn is triangular (Pl. LVIII, 26, 26) or trapezoid (Pl. LVIII, 16, le). It is up to 7 μm high. Both fragments participate in its structure without the formation of a pericoel. The antapical horns are strongly reduced and practically are not expressed logically.
The periphragm is delicate, transparent, and has a distinct granular-fine mesh structure (Pl. LVIII, 26, 36). The penitabular ridges are formed by relatively large granules, and are clearly visible (Pl. LVII, 1-6; LVIII, 2a-2g) or not quite clearly (Pl. LVIII, 1a-1g, 3a-3g). The intratabular granular granules are significantly smaller than the penitabular ones, are linearly closed, and in terms of the surface form a pattern of nested concentric polyhedrons, repeating the convolutions of the paratabulation plates. The sizes of these granules vary from small, visible only at high magnification (Pl. LVIII, 1, 3), to relatively large (Pl. LVIII, 2a, plate 1'", 4a, parasulcus, 9a, plates 3", 4", 4'"). At the same time, with the increase in the size of the granules, the fine reticulation of the periphragm increases proportionally and becomes distinct (Pl. LVII, 1, 2, 8, 9). The endophragm is thicker than the periphragm, dense. The fragments are pressed against each other and participate in the formation of the apical horn, parasutural and penitabular ridges without the formation of the pericoel. The pandasutural areas are expressed both in plan (Pl. LVII, 7-9) and in section (Pl. LVIII, 28, 36), have a width of up to 4 µm. The ridges are low (up to 3 µm).
Paracingulum (up to 8 µm) helicoid, twisted to the left by a value slightly greater than the width, its ends narrowing (up to 3.5 µm), tabulation indistinct. Parasulcus narrow, widening towards the antapex at the cingulum. Archaeopile large, intercalary, combined, type 31, operculum free.
Holotype. Plate LVII, 1-9. Prep. 174-7-25 (coordinates relative to the lower left corner of the coverslip: 46.5 × 1.9). Paratypes, same preparation (Plate LVIII): first la-1g (57.5 x 5.3); second 20-22 (47.2 x 7.3); third За-3g (49.7 x 7.3).
Location. Barashivska amber-bearing zone, Viktorovskaya area, Mezhyhirya suite (Zhytomyr region, Emilchansky district).
Dimensions (µm). Holotype: pericyst length 46; pericyst width 40; apical horn height 6; paracingulum width up to 7. Other specimens (15 specimens): pericyst length 34-46; pericyst width 31-40; apical horn height 4.5-7; paracingulum width 6-8.
Comparison. Based on the nature of the structure of the peri and endophragm, as well as the sculpture of the surface of the paratabulation plates, the species can be compared with the species Ph. filigranum (Benedek) Benedek et Sarjeant, 1981. Our specimens differ from the latter in: larger size; roundness of the general outline of the cyst; almost complete reduction of the antapical horns; participation in the structure of the apical horn, singular, pandasutural and penitabular ridges of both layers of the cyst and the absence of cavity.
Distribution. Ukraine, Zhitomir region, Yemilchansky district, Barashivska amber-bearing zone, Viktorovskaya area, Mezhyhirya suite, Lower Oligocene (Oligocene).
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Original description: [Andreeva-Grigorovich et al., 2011] (translated from Russian):
Phthanoperidinium zosimovichi Stotland sp. nov. Tables LVII, 1-9; LVIII, 1-3
Name. In honor of Vladimir Yuryevich Zosimovich, a famous paleontologist and stratigrapher of the Cenozoic of Ukraine.
Diagnosis. Round-elliptical, acavate peridiniacean cyst, dorsoventrally weak-ly compressed, paratabulation expressed by short penitabular ridges and intrata-bular fine-grained-reticulate structures of plates and pandasutural zones. Apical horn is triangular-trapeziform, antapical horns very much reduced and invisible.
Description. An aquatic cyst with peridinioid paratabulation. The outline in the dorsoventral plane is rounded-elliptical. The "compression" coefficient is 0.6-0.7. The epicysta is equal in length to the hypocyst. The apical horn is triangular (Pl. LVIII, 26, 26) or trapezoid (Pl. LVIII, 16, le). It is up to 7 μm high. Both fragments participate in its structure without the formation of a pericoel. The antapical horns are strongly reduced and practically are not expressed logically.
The periphragm is delicate, transparent, and has a distinct granular-fine mesh structure (Pl. LVIII, 26, 36). The penitabular ridges are formed by relatively large granules, and are clearly visible (Pl. LVII, 1-6; LVIII, 2a-2g) or not quite clearly (Pl. LVIII, 1a-1g, 3a-3g). The intratabular granular granules are significantly smaller than the penitabular ones, are linearly closed, and in terms of the surface form a pattern of nested concentric polyhedrons, repeating the convolutions of the paratabulation plates. The sizes of these granules vary from small, visible only at high magnification (Pl. LVIII, 1, 3), to relatively large (Pl. LVIII, 2a, plate 1'", 4a, parasulcus, 9a, plates 3", 4", 4'"). At the same time, with the increase in the size of the granules, the fine reticulation of the periphragm increases proportionally and becomes distinct (Pl. LVII, 1, 2, 8, 9). The endophragm is thicker than the periphragm, dense. The fragments are pressed against each other and participate in the formation of the apical horn, parasutural and penitabular ridges without the formation of the pericoel. The pandasutural areas are expressed both in plan (Pl. LVII, 7-9) and in section (Pl. LVIII, 28, 36), have a width of up to 4 µm. The ridges are low (up to 3 µm).
Paracingulum (up to 8 µm) helicoid, twisted to the left by a value slightly greater than the width, its ends narrowing (up to 3.5 µm), tabulation indistinct. Parasulcus narrow, widening towards the antapex at the cingulum. Archaeopile large, intercalary, combined, type 31, operculum free.
Holotype. Plate LVII, 1-9. Prep. 174-7-25 (coordinates relative to the lower left corner of the coverslip: 46.5 × 1.9). Paratypes, same preparation (Plate LVIII): first la-1g (57.5 x 5.3); second 20-22 (47.2 x 7.3); third За-3g (49.7 x 7.3).
Location. Barashivska amber-bearing zone, Viktorovskaya area, Mezhyhirya suite (Zhytomyr region, Emilchansky district).
Dimensions (µm). Holotype: pericyst length 46; pericyst width 40; apical horn height 6; paracingulum width up to 7. Other specimens (15 specimens): pericyst length 34-46; pericyst width 31-40; apical horn height 4.5-7; paracingulum width 6-8.
Comparison. Based on the nature of the structure of the peri and endophragm, as well as the sculpture of the surface of the paratabulation plates, the species can be compared with the species Ph. filigranum (Benedek) Benedek et Sarjeant, 1981. Our specimens differ from the latter in: larger size; roundness of the general outline of the cyst; almost complete reduction of the antapical horns; participation in the structure of the apical horn, singular, pandasutural and penitabular ridges of both layers of the cyst and the absence of cavity.
Distribution. Ukraine, Zhitomir region, Yemilchansky district, Barashivska amber-bearing zone, Viktorovskaya area, Mezhyhirya suite, Lower Oligocene (Oligocene).