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Pentadinium rugosum
Materials examined: Eleven specimens.
Etymology: The name is derived from the Latin rugosus – wrinkled, corrugated. The name is indicative of the paraplate ornamentation shaped as kinked folds, wrinkles.
Holotype: Fig. 6A, B. The Crimean Peninsula, Bakhchisarai section, the Kuma Formation, interval 4, sample 539, coll. cat. no. preparation B539-A. Middle Eocene. Dimensions: length in the apical-antapical position – 57.6 lm, total width – 64.8 lm, endocyst diameter – 54.0 lm, pericoel height – 7.2 lm.
Paratype: Fig. 6E. The Lower Volga region, Ravninnaya R-43 well, the Solonka Formation, sample 67, coll. cat. no. preparation R-43-67-A. Middle Eocene. Dimensions: length in the apical-antapical position – 55.8 lm, total width – 61.2 lm, endocyst diameter – 50.4 lm, pericoel height – 7.0 lm.
Diagnosis: Cysts proximochorate, subspherical in shape, slightly asymmetrical due to the presence of pericoel on the ventral surface. Endophragm dense, granulate or acinose. Periphragm thin, smooth, transparent, forming low parasutural folds with narrow pericoels along the paraplate outlines, making tabulation better pronounced. Periphragm forms thin cordlike folds on the paraplates surfaces, making cysts characteristically wrinkled in appearance. Periphragm makes a large pericoel on the cyst ventral surface. Archaeopyle precingular, type P (3’’). Operculum free.
Description: Cysts round, subspherical shape. Endophragm dense, granulate or acinose. Cyst tabulation accentuated with periphragm thin sutural folds with narrow pericoel in its base. Periphragm bears against the endophragm; thin cordlike wrinkles and warts on the plates, reminiscent of Arabian ornate lettering. On cyst ventral surface, the periphragm separated from the endophragm, making a clearly discernible pericoel (Fig. 6A, D, E). In cyst apical and antapical positions, a break in periphragm observed in the ventral pericoel zone (Fig. 6B, I, J). Paracingulum narrow. Archaeopyle precingular, type P (3’’), operculum free. Gonyaulacoid tabulation defined with periphragm folds and partially with the paraplate ornamentation: 4’, 6”, ? 6c, 6”’, 1p, 1””.
Dimensions: Cyst length in the apical-antapical position – 46.8–57.8 lm; pericyst diameter – 57.6–72.0 lm; endocyst diameter – 46.8–57.6 lm. 11 specimens measured.
Variability: The character and the intensity of the plate ornamentations vary.
Comparison: Pentadinium rugosum n. sp. differs from all other Pentadinium species in the presence of a well-developed (distinct) pericoel on the ventral side of the cyst and the characteristic, wrinkled texture of the periphragm. Pentadinium goniferum Gerlach also has a wide pericoel, which, unlike P. rugosum n. sp., located in the equatorial zone of the cyst. In addition, P. goniferum is ornamented with gonal protrusions, which are absent in P. rugosum n. sp. A relatively wide parasuture pericoel is observed in Pentadinium membranaceum (Eisenack), P. taeniagerum Gerlach, P. granulatum (Gocht), P. favatum Edwards, and P. alabamensis Quajtaal and Brinkhuis, but the latter differ in the texture of the endophragm — honeycomb, scabrate, or vermiculate ones and the location of the pericoel. In addition, P. alabamensis differs from P. rugosum n. sp. extremely pronounced separation of the walls and perforated structure of the periphragm. P. netangei Zhao and Morzadec–Kerfourn, P.? circumsutum (Morgenroth) have a microgranular periphragm. P.? circumsutum, P. membranaceum, and P. sabulum Fensome et al., in contrast to P. rugosum n. sp., have higher parasutural folds. Species Pentadinium lophophorum (Benedek) differs from P. rugosum n. sp. more prominent wall ornamentation in the form of well-developed tubercles, high paracingular folds of periphragm, wide cingulum, and absence of ventral pericoel. In the species Pentadinium omasum Harding, in contrast to P. rugosum n. sp., the structure of the periphragm is pseudopunctate; the cavation is limited to the dorsal surface of the cyst. Pentadinium polypodum Edwards, P. spinulum Straussand and Lund, P. galileoi Sancay et al., differ from P. rugosum n. sp. by relatively smooth endophragm and development of protrusions. Pentadinium laticinctum Gerlach, is comparable to P. rugosum n. sp. according to the degree of relief of the endophragm and the character of tabulation, but differs in the ornamentation of the periphragm and the absence of ventral separation of the walls.
The new species is comparable to Pentadinium specimens diagnosed by De Coninck as Impagidinium sp. cf. I. multiplex (Wall and Dale), consistent with its ventral pericoel and relatively low-relief tabulation (De Coninck, 1986, pl. 4, figs. 14, 15, 19, 20), but distinguished by the characteristic cord-like texture of the periphragm. Occurrence: The Crimean Peninsula, the Kuma Formation (upper part) in the section from Bakhchisarai. The Lower Volga Region near Volgograd (Ravninnaya R-43 well) and the Southern Ergeni (Keresta-1 well), the Solonka Formation. Middle Eocene.
Etymology: The name is derived from the Latin rugosus – wrinkled, corrugated. The name is indicative of the paraplate ornamentation shaped as kinked folds, wrinkles.
Holotype: Fig. 6A, B. The Crimean Peninsula, Bakhchisarai section, the Kuma Formation, interval 4, sample 539, coll. cat. no. preparation B539-A. Middle Eocene. Dimensions: length in the apical-antapical position – 57.6 lm, total width – 64.8 lm, endocyst diameter – 54.0 lm, pericoel height – 7.2 lm.
Paratype: Fig. 6E. The Lower Volga region, Ravninnaya R-43 well, the Solonka Formation, sample 67, coll. cat. no. preparation R-43-67-A. Middle Eocene. Dimensions: length in the apical-antapical position – 55.8 lm, total width – 61.2 lm, endocyst diameter – 50.4 lm, pericoel height – 7.0 lm.
Diagnosis: Cysts proximochorate, subspherical in shape, slightly asymmetrical due to the presence of pericoel on the ventral surface. Endophragm dense, granulate or acinose. Periphragm thin, smooth, transparent, forming low parasutural folds with narrow pericoels along the paraplate outlines, making tabulation better pronounced. Periphragm forms thin cordlike folds on the paraplates surfaces, making cysts characteristically wrinkled in appearance. Periphragm makes a large pericoel on the cyst ventral surface. Archaeopyle precingular, type P (3’’). Operculum free.
Description: Cysts round, subspherical shape. Endophragm dense, granulate or acinose. Cyst tabulation accentuated with periphragm thin sutural folds with narrow pericoel in its base. Periphragm bears against the endophragm; thin cordlike wrinkles and warts on the plates, reminiscent of Arabian ornate lettering. On cyst ventral surface, the periphragm separated from the endophragm, making a clearly discernible pericoel (Fig. 6A, D, E). In cyst apical and antapical positions, a break in periphragm observed in the ventral pericoel zone (Fig. 6B, I, J). Paracingulum narrow. Archaeopyle precingular, type P (3’’), operculum free. Gonyaulacoid tabulation defined with periphragm folds and partially with the paraplate ornamentation: 4’, 6”, ? 6c, 6”’, 1p, 1””.
Dimensions: Cyst length in the apical-antapical position – 46.8–57.8 lm; pericyst diameter – 57.6–72.0 lm; endocyst diameter – 46.8–57.6 lm. 11 specimens measured.
Variability: The character and the intensity of the plate ornamentations vary.
Comparison: Pentadinium rugosum n. sp. differs from all other Pentadinium species in the presence of a well-developed (distinct) pericoel on the ventral side of the cyst and the characteristic, wrinkled texture of the periphragm. Pentadinium goniferum Gerlach also has a wide pericoel, which, unlike P. rugosum n. sp., located in the equatorial zone of the cyst. In addition, P. goniferum is ornamented with gonal protrusions, which are absent in P. rugosum n. sp. A relatively wide parasuture pericoel is observed in Pentadinium membranaceum (Eisenack), P. taeniagerum Gerlach, P. granulatum (Gocht), P. favatum Edwards, and P. alabamensis Quajtaal and Brinkhuis, but the latter differ in the texture of the endophragm — honeycomb, scabrate, or vermiculate ones and the location of the pericoel. In addition, P. alabamensis differs from P. rugosum n. sp. extremely pronounced separation of the walls and perforated structure of the periphragm. P. netangei Zhao and Morzadec–Kerfourn, P.? circumsutum (Morgenroth) have a microgranular periphragm. P.? circumsutum, P. membranaceum, and P. sabulum Fensome et al., in contrast to P. rugosum n. sp., have higher parasutural folds. Species Pentadinium lophophorum (Benedek) differs from P. rugosum n. sp. more prominent wall ornamentation in the form of well-developed tubercles, high paracingular folds of periphragm, wide cingulum, and absence of ventral pericoel. In the species Pentadinium omasum Harding, in contrast to P. rugosum n. sp., the structure of the periphragm is pseudopunctate; the cavation is limited to the dorsal surface of the cyst. Pentadinium polypodum Edwards, P. spinulum Straussand and Lund, P. galileoi Sancay et al., differ from P. rugosum n. sp. by relatively smooth endophragm and development of protrusions. Pentadinium laticinctum Gerlach, is comparable to P. rugosum n. sp. according to the degree of relief of the endophragm and the character of tabulation, but differs in the ornamentation of the periphragm and the absence of ventral separation of the walls.
The new species is comparable to Pentadinium specimens diagnosed by De Coninck as Impagidinium sp. cf. I. multiplex (Wall and Dale), consistent with its ventral pericoel and relatively low-relief tabulation (De Coninck, 1986, pl. 4, figs. 14, 15, 19, 20), but distinguished by the characteristic cord-like texture of the periphragm. Occurrence: The Crimean Peninsula, the Kuma Formation (upper part) in the section from Bakhchisarai. The Lower Volga Region near Volgograd (Ravninnaya R-43 well) and the Southern Ergeni (Keresta-1 well), the Solonka Formation. Middle Eocene.