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Alterbidinium nuculum
From Fensome et al., 2019:
Alterbidinium nuculum, Vasilyeva in Andreeva-Grigorovich et al., 2011, p.42–43, pl.11, figs.5–8,11–14; text-fig.18b ex Williams and Fensome, 2016, p.138.
Holotype: Andreeva-Grigorovich et al., 2011, pl.11, figs.5–6; text-fig.18b, designated by Williams and Fensome (2016, p.138).
This name was not validly published by Vasilyeva in Andreeva-Grigorovich et al. (2011, p.42–43) since the holotype citation (pl.11, figs.5–8,11–14 and text-fig.18b) includes more than one specimen. The holotype was clearly designated in Williams and Fensome (2016), thus validating the name Alterbidinium nuculum.
Age: Thanetian–Ypresian.
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Original description: [Vasilyeva in Andreeva-Grigorovich et al., 2011, p.42–43] (translated from Russian with Google Translate):
Alterbidinium nuculum Vassilyeva sp. nov. Plate XI, 5-8, 11-14; Fig. 18, b
Name: From Latin nucula - nut.
Diagnosis. Peridinoid oval-pentagonal wide cyst of medium size. The left antapical horn is developed, the right one is significantly reduced. The epicyst is helmet-shaped with a protruding truncated apex. The hypocyst is trapezoid, asymmetrical. The endocyst is round, round-pentagonal. The periphragm is dense, granular, tuberculate. The endophragm is thick, two-layered, coarse-grained, tuberculate. The periarchaeopyle is wide, round-pentagonal. The perioperculum is attached. The parasulcus is indicated by two folds of the periphragm on the ventral side of the hypocyst.
Diagnosis. Peridinioid, oval-pentagonal, widely ellipsoidal cyst of intermedia-te size. Left antapical horn developed. Right antapical horn considerably reduced. Epicyst helmet-shaped with a small cut off apical horn. Hipocyst trapezi-form asymmetrical. Endocyst rounded, circular-pentagonal. Periphragm dense, granular, coarse granular. Endophragm thick, bilayered, coarse granular, scabrate. Periarcheopyle wide, round-pentagonal. Perioperculum attached. Parasulcus marked by two folds of periphragm on hypocyst ventral side.
Description. The pericyst is of the peridinoid type, oval-pentagonal, with one apical and two antapical unequal horns. The epicyst is slightly larger than the hypocyst. The epicyst is helmet-shaped, dome-shaped, sometimes with pronounced shoulders and a truncated apex. The hypocyst is trapezoidal with two well-defined, short, pointed antapical horns; the right one is slightly longer than the left. The endocyst is round, sometimes slightly pentagonal. The pericoel is well defined, narrowing in the region of the cingulum. The epicoel is helmet-shaped, voluminous. The hypocoel is significantly narrower. The periphragm is transparent, slightly granular, dense, rigid, and retains its shape well. The endophragm is thick, two-layered; the outer layer is tuberculate. In plan, the endophragm is coarse-grained, with visible striation. On the surface of the endophragm there are inclusions of organic material in the form of dark round spots. Due to the structure of the endophragm, the endocyst looks like a dense nut. The paracingulum is well expressed as a groove with raised edges. The periarchaeopile is rounded-hexagonal, elongated, intercalary in position. The periarchaeopile is significantly larger than the endoarchaeopile. The operculum is attached. The paratabulation is unclear, marked by the archaeopile and cingulum. The parasulcus is unclear.
Holotype. Plate XI, 5-8, 11-14; Fig. 18, b. Prep. Persh. 116-2003, IGIG UB RAS.
Location. Pershinsky quarry, Serov suite (Sverdlovsk region, Dalmatovo village).
Dimensions (µm). Holotype: pericyst length 56.1; pericyst width 42.9; endocyst length 35.0. Other specimens (7 specimens): pericyst length - 61.1-55.0; pericyst width 44.0-41.2; endocyst length - 37.2-36.0; endocyst width 36-35.
Comparison. This species is comparable to the species Alterbidinium rugulum Iakovleva et Kulkova, 2001, but differs from the latter in its more convex, helmet-shaped form of the epicyst, antapical horns of unequal length, and thick, dense, tuberous, usually dark endophragm. Alterbidinium nuculum differs from the species Alterbidinium saltanovae by wider cyst proportions, rounded rather than elongated endocyst.
Distribution. Russia, Middle Trans-Urals, Talitskaya suite (Upper Talitskaya subsuite), Serovskaya suite. Paleocene - Lower Eocene.
Alterbidinium nuculum, Vasilyeva in Andreeva-Grigorovich et al., 2011, p.42–43, pl.11, figs.5–8,11–14; text-fig.18b ex Williams and Fensome, 2016, p.138.
Holotype: Andreeva-Grigorovich et al., 2011, pl.11, figs.5–6; text-fig.18b, designated by Williams and Fensome (2016, p.138).
This name was not validly published by Vasilyeva in Andreeva-Grigorovich et al. (2011, p.42–43) since the holotype citation (pl.11, figs.5–8,11–14 and text-fig.18b) includes more than one specimen. The holotype was clearly designated in Williams and Fensome (2016), thus validating the name Alterbidinium nuculum.
Age: Thanetian–Ypresian.
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Original description: [Vasilyeva in Andreeva-Grigorovich et al., 2011, p.42–43] (translated from Russian with Google Translate):
Alterbidinium nuculum Vassilyeva sp. nov. Plate XI, 5-8, 11-14; Fig. 18, b
Name: From Latin nucula - nut.
Diagnosis. Peridinoid oval-pentagonal wide cyst of medium size. The left antapical horn is developed, the right one is significantly reduced. The epicyst is helmet-shaped with a protruding truncated apex. The hypocyst is trapezoid, asymmetrical. The endocyst is round, round-pentagonal. The periphragm is dense, granular, tuberculate. The endophragm is thick, two-layered, coarse-grained, tuberculate. The periarchaeopyle is wide, round-pentagonal. The perioperculum is attached. The parasulcus is indicated by two folds of the periphragm on the ventral side of the hypocyst.
Diagnosis. Peridinioid, oval-pentagonal, widely ellipsoidal cyst of intermedia-te size. Left antapical horn developed. Right antapical horn considerably reduced. Epicyst helmet-shaped with a small cut off apical horn. Hipocyst trapezi-form asymmetrical. Endocyst rounded, circular-pentagonal. Periphragm dense, granular, coarse granular. Endophragm thick, bilayered, coarse granular, scabrate. Periarcheopyle wide, round-pentagonal. Perioperculum attached. Parasulcus marked by two folds of periphragm on hypocyst ventral side.
Description. The pericyst is of the peridinoid type, oval-pentagonal, with one apical and two antapical unequal horns. The epicyst is slightly larger than the hypocyst. The epicyst is helmet-shaped, dome-shaped, sometimes with pronounced shoulders and a truncated apex. The hypocyst is trapezoidal with two well-defined, short, pointed antapical horns; the right one is slightly longer than the left. The endocyst is round, sometimes slightly pentagonal. The pericoel is well defined, narrowing in the region of the cingulum. The epicoel is helmet-shaped, voluminous. The hypocoel is significantly narrower. The periphragm is transparent, slightly granular, dense, rigid, and retains its shape well. The endophragm is thick, two-layered; the outer layer is tuberculate. In plan, the endophragm is coarse-grained, with visible striation. On the surface of the endophragm there are inclusions of organic material in the form of dark round spots. Due to the structure of the endophragm, the endocyst looks like a dense nut. The paracingulum is well expressed as a groove with raised edges. The periarchaeopile is rounded-hexagonal, elongated, intercalary in position. The periarchaeopile is significantly larger than the endoarchaeopile. The operculum is attached. The paratabulation is unclear, marked by the archaeopile and cingulum. The parasulcus is unclear.
Holotype. Plate XI, 5-8, 11-14; Fig. 18, b. Prep. Persh. 116-2003, IGIG UB RAS.
Location. Pershinsky quarry, Serov suite (Sverdlovsk region, Dalmatovo village).
Dimensions (µm). Holotype: pericyst length 56.1; pericyst width 42.9; endocyst length 35.0. Other specimens (7 specimens): pericyst length - 61.1-55.0; pericyst width 44.0-41.2; endocyst length - 37.2-36.0; endocyst width 36-35.
Comparison. This species is comparable to the species Alterbidinium rugulum Iakovleva et Kulkova, 2001, but differs from the latter in its more convex, helmet-shaped form of the epicyst, antapical horns of unequal length, and thick, dense, tuberous, usually dark endophragm. Alterbidinium nuculum differs from the species Alterbidinium saltanovae by wider cyst proportions, rounded rather than elongated endocyst.
Distribution. Russia, Middle Trans-Urals, Talitskaya suite (Upper Talitskaya subsuite), Serovskaya suite. Paleocene - Lower Eocene.