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Impagidinium tuberculatum
Original description: [Vasilyeva, 2024, p. 5, 7]:
Impagidinium tuberculatum sp. nov.
Plate 2, figures 1–12; Figure 4
2020 Impagidinium sp. 1 – Vasilyeva, p. 11, pl. II, fig. 15.
Derivation of name. Named after the Latin tuberculatus – torulose, in regard to periphragm ornamentation.
Holotype. Plate 2, figures 1, 2, slide R43/57B, coordinates 87 x 25, dorsal view, Ravninnaya R43 borehole, sample R43-57, collection number IGG-2/23-03. Specimen dimensions: total length 61 μm, total width 47 μm; central body length 48 μm, central body width 34 μm, height of septa 6 mm; apical horn length 7 μm.
Paratype. Plate 2, figure 8, slide R43/46B, coordinates 91 x 16, lateral view, Ravninnaya R43 borehole, sample R43-46, collection number IGG-2/23-04. Specimen dimensions: total length 57 μm, total width 50 μm, central body length 43 μm, central body width 34 μm, height of septa 4 mm, apical horn length 7 μm.
Type locality. The village of Ravninny in the vicinity of Volgograd, Volgograd region, Russia.
Type stratum. The Keresta Formation, Volga–Caspian subregion.
Diagnosis. Gonyaulacoid proximate cyst of oval or ovoidaloval shape, with a small apical horn. High sutural septa and relief of intratabular plate ornamentation emphasise the gonyaulacoidal tabulation. Archaeopyle is large, precingular, type P (3ʺ), free operculum. The last precingular plate (6ʺ) is triangular, has a short contact with the last apical plate 4'. Cingulum is laevorotatory.
Description. Impagidinium cysts oval in shape, with high septa and a small apical horn. The phragm is dense, twolayers. The periphragm surface is punctate and additionally ornamented with large tubercules of intratabular arrangement. The tubercules are rotund, oval or elongated, vermiform. The ornamented zones on the plates are clearly outlined, which makes them look like undulose shields (Plate 2, figures 4, 8, 12). Sutural septa are high, thin, transparent, vertically striated, occasionally grainy and perforated; the edge is firm, slightly undulating or crenulate (Plate 2, figures 2, 6). The cingulum is laevorotatory, wide, formed by hexangular plates; the surface is slightly ornamented with tubercules (Plate 2, figure 7). Divergence of the cingulum ends is larger than its width (about 8 mm). Ornamented plates and septa emphasise the gonyaulacoidal tabulation of the cyst 4', 6ʺ, 6c, 6ʺ', 1p, 1ʺʺ (Figure 4). Archaeopyle is precingular, type P (3ʺ), operculum is free. The last precingular plate 6ʺ is triangular and has a short contact with the last apical plate 4' (Plate 2, figures 5, 6). Plates 1' and 4' are narrow, elongated, indistinctly separated from each other (Plate 2, figure 9). Sulcus comparatively wide, slightly inclined, indistinctly divided into plates (Plate 2, figure 7).
Dimensions. Cyst total length 57 (60) 68 μm; cyst total width 36 (48) 50 μm; endocyst length 41 (47) 50 μm; endocyst width 34 (38) 41 μm; height of septa 4–7 mm; apical horn height 6–7 μm; cingulum width 5–7 μm. Number of specimens measured: 12.
Comparison. The new taxon differs from all other species of the genus Impagidinium in the combination of three features: oval shape, apical horn and large-tuberculate intratabular ornamentation of the periphragm. The formation of an apical horn or projection is not common in the genus Impagidinium (Stover and Evitt 1978). Impagidinium tuberculatum sp. nov. is comparable to Impagidinium aspinatum in the presence of an apical horn and oval body shape; however, it differs from the latter in having a shorter, bluntly shaped apical horn and large tuberculate, worm-like ornamentation of the plates. Impagidinium tuberculatum sp. nov. is comparable to Impagidinium maculatum in terms of the
broad-oval body shape and relief ornamentation of the periphragm, but differs in the coarse tuberculate structure of the periphragm and the presence of an apical horn. The species described here is comparable to Impagidinium cassiculus in body shape, but the latter has a large reticulated periphragm. Impagidinium dispertitum, in contrast to Impagidinium tuberculatum sp. nov., is ornamented with sparsely spaced granules and lacks an apical horn. Impagidinium tuberculatum sp. nov. is comparable to Impagidinium ‘waipanense’ in cyst shape and having a distinct apical horn; however, the latter differs in the structure of the sixth precingular plate (6ʺ or 1i) and its contact with the apical plates on the ventral surface, which served as the basis for assigning the species to the genus Ynezidinium (Lucas-Clark and Helenes 2000).
Occurrence. South of the Russian Platform, the Keresta Formation in the Ravninnayay R43 borehole, Volgograd Volga region; Keresta-1 borehole, the Yergeni Hills. Middle Eocene, Lutetian stage.
Impagidinium tuberculatum sp. nov.
Plate 2, figures 1–12; Figure 4
2020 Impagidinium sp. 1 – Vasilyeva, p. 11, pl. II, fig. 15.
Derivation of name. Named after the Latin tuberculatus – torulose, in regard to periphragm ornamentation.
Holotype. Plate 2, figures 1, 2, slide R43/57B, coordinates 87 x 25, dorsal view, Ravninnaya R43 borehole, sample R43-57, collection number IGG-2/23-03. Specimen dimensions: total length 61 μm, total width 47 μm; central body length 48 μm, central body width 34 μm, height of septa 6 mm; apical horn length 7 μm.
Paratype. Plate 2, figure 8, slide R43/46B, coordinates 91 x 16, lateral view, Ravninnaya R43 borehole, sample R43-46, collection number IGG-2/23-04. Specimen dimensions: total length 57 μm, total width 50 μm, central body length 43 μm, central body width 34 μm, height of septa 4 mm, apical horn length 7 μm.
Type locality. The village of Ravninny in the vicinity of Volgograd, Volgograd region, Russia.
Type stratum. The Keresta Formation, Volga–Caspian subregion.
Diagnosis. Gonyaulacoid proximate cyst of oval or ovoidaloval shape, with a small apical horn. High sutural septa and relief of intratabular plate ornamentation emphasise the gonyaulacoidal tabulation. Archaeopyle is large, precingular, type P (3ʺ), free operculum. The last precingular plate (6ʺ) is triangular, has a short contact with the last apical plate 4'. Cingulum is laevorotatory.
Description. Impagidinium cysts oval in shape, with high septa and a small apical horn. The phragm is dense, twolayers. The periphragm surface is punctate and additionally ornamented with large tubercules of intratabular arrangement. The tubercules are rotund, oval or elongated, vermiform. The ornamented zones on the plates are clearly outlined, which makes them look like undulose shields (Plate 2, figures 4, 8, 12). Sutural septa are high, thin, transparent, vertically striated, occasionally grainy and perforated; the edge is firm, slightly undulating or crenulate (Plate 2, figures 2, 6). The cingulum is laevorotatory, wide, formed by hexangular plates; the surface is slightly ornamented with tubercules (Plate 2, figure 7). Divergence of the cingulum ends is larger than its width (about 8 mm). Ornamented plates and septa emphasise the gonyaulacoidal tabulation of the cyst 4', 6ʺ, 6c, 6ʺ', 1p, 1ʺʺ (Figure 4). Archaeopyle is precingular, type P (3ʺ), operculum is free. The last precingular plate 6ʺ is triangular and has a short contact with the last apical plate 4' (Plate 2, figures 5, 6). Plates 1' and 4' are narrow, elongated, indistinctly separated from each other (Plate 2, figure 9). Sulcus comparatively wide, slightly inclined, indistinctly divided into plates (Plate 2, figure 7).
Dimensions. Cyst total length 57 (60) 68 μm; cyst total width 36 (48) 50 μm; endocyst length 41 (47) 50 μm; endocyst width 34 (38) 41 μm; height of septa 4–7 mm; apical horn height 6–7 μm; cingulum width 5–7 μm. Number of specimens measured: 12.
Comparison. The new taxon differs from all other species of the genus Impagidinium in the combination of three features: oval shape, apical horn and large-tuberculate intratabular ornamentation of the periphragm. The formation of an apical horn or projection is not common in the genus Impagidinium (Stover and Evitt 1978). Impagidinium tuberculatum sp. nov. is comparable to Impagidinium aspinatum in the presence of an apical horn and oval body shape; however, it differs from the latter in having a shorter, bluntly shaped apical horn and large tuberculate, worm-like ornamentation of the plates. Impagidinium tuberculatum sp. nov. is comparable to Impagidinium maculatum in terms of the
broad-oval body shape and relief ornamentation of the periphragm, but differs in the coarse tuberculate structure of the periphragm and the presence of an apical horn. The species described here is comparable to Impagidinium cassiculus in body shape, but the latter has a large reticulated periphragm. Impagidinium dispertitum, in contrast to Impagidinium tuberculatum sp. nov., is ornamented with sparsely spaced granules and lacks an apical horn. Impagidinium tuberculatum sp. nov. is comparable to Impagidinium ‘waipanense’ in cyst shape and having a distinct apical horn; however, the latter differs in the structure of the sixth precingular plate (6ʺ or 1i) and its contact with the apical plates on the ventral surface, which served as the basis for assigning the species to the genus Ynezidinium (Lucas-Clark and Helenes 2000).
Occurrence. South of the Russian Platform, the Keresta Formation in the Ravninnayay R43 borehole, Volgograd Volga region; Keresta-1 borehole, the Yergeni Hills. Middle Eocene, Lutetian stage.