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Dingodinium nequeas
From Fensome et al., 2019:
Dingodinium nequeas Pestchevitskaya, 2018, p.102, pl.9, figs.1–8. Holotype: Pestchevitskaya, 2018, pl.9, figs.1–6. Pestchevitskaya (2018, p.102) indicated that the epithet is a Latin adjective for smooth; as we could not trace this derivation, we retain it in its original form, although "nequeum" may be the correct spelling. Age: late Kimmeridgian.
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Original description: [Pestchevitskaya, 2018]:
Dingodinium nequeas Pestchevitskaya, sp. nov.
Plate 9, figs. 1–8
E t y m o l o g y. From the Latin nequeas (smooth), to describe the ornamentation of the endocyst.
H o l o t y p e. TsGM, preparation 327, specimen no. 327.3/11.5-100, dinoflagellate cysts; Ulyanovsk Region; Gorodishche Section, Bed 1; Upper Kimmeridgian; designated here (Pl. 9, figs. 1–6).
D i a g n o s i s. Proximate, camocavate dinocysts with combination archeopyle of composite type pr[tA1–4]a1–3. Pericyst thin, transparent, smooth; form rounded, with short, wide, conical apical horn. Endocyst thicker, shagreenate or fine-grained; form rounded. Pericoel narrow. Tabulation of cladopixiaceous type, expressed by sutural features, may be stressed by folds and very low psilate crests on pericyst, formula 1pr, 4', 3a, 7'', Xc, 6''', 1p, 1''''. Cingulum and sulcus are expressed by sutural features, may be emphasized by folds and very low psilate crests on
pericyst.
D e s c r i p t i o n. The dinocysts are proximate, camocavate, with a combination archeopyle of composite type pr[tA1–4]a1–3. The pericyst is rounded, with a length almost equaling its width, in the apical area forming a wide-conical horn. The endocyst is spherical. The pericoel is narrow, can be absent on the dorsal side and in the region of the intercalary plates. The periphragm is transparent, thin, easily folded, generally smooth, but can be finely granulate in the horn region. The endophragm is denser, shagreenate or finely granulate. The tabulation is of the cladopixiaceous type, expressed on the endocyst by sutural features, and emphasized by very low, smooth crests and folds on the pericyst. In the apical area, the septa become narrower; the tabulation is usually expressed by sutural features. The tabulation formula is 1pr, 4', 3a, 7'', Xc, 6''', 1p, 1''''. The cingulum and sulcus are expressed on the pericyst by very low crests and are usually emphasized by folds, and on the endocyst by sutural features.
Dimensions in μm. Holotype: pericyst length = 48, width = 37, endocyst length = 37, width = 35, pericoel width on the dorsal side = 4, length of the apical horn = 8, width = 9, height crests = 0.5–1. The mean values in 10 specimens: pericyst length = 32–55, width = 27–49, endocyst length = 26–45, width = 24–45, pericoel width on the dorsal side = 4–6, length of the apical horn = 5–9, width = 9–12, height of the crests = 0.5–1.
C o m p a r i s o n. This species is distinguished from the morphologically similar species D. cooksoniae, D. harsveldtii (Herngreen et al., 1984), D. albertii and D. tuberosum by the smoothened ornamentation of the endocyst. This feature in the new species makes its similar to D. europaeum, characterized by a smooth endocyst, although the pericoel in the latter species is considerably wider than in D. nequeas.
O c c u r r e n c e. See Fig. 1.
M a t e r i a l. 10 well-preserved specimens.
Dingodinium nequeas Pestchevitskaya, 2018, p.102, pl.9, figs.1–8. Holotype: Pestchevitskaya, 2018, pl.9, figs.1–6. Pestchevitskaya (2018, p.102) indicated that the epithet is a Latin adjective for smooth; as we could not trace this derivation, we retain it in its original form, although "nequeum" may be the correct spelling. Age: late Kimmeridgian.
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Original description: [Pestchevitskaya, 2018]:
Dingodinium nequeas Pestchevitskaya, sp. nov.
Plate 9, figs. 1–8
E t y m o l o g y. From the Latin nequeas (smooth), to describe the ornamentation of the endocyst.
H o l o t y p e. TsGM, preparation 327, specimen no. 327.3/11.5-100, dinoflagellate cysts; Ulyanovsk Region; Gorodishche Section, Bed 1; Upper Kimmeridgian; designated here (Pl. 9, figs. 1–6).
D i a g n o s i s. Proximate, camocavate dinocysts with combination archeopyle of composite type pr[tA1–4]a1–3. Pericyst thin, transparent, smooth; form rounded, with short, wide, conical apical horn. Endocyst thicker, shagreenate or fine-grained; form rounded. Pericoel narrow. Tabulation of cladopixiaceous type, expressed by sutural features, may be stressed by folds and very low psilate crests on pericyst, formula 1pr, 4', 3a, 7'', Xc, 6''', 1p, 1''''. Cingulum and sulcus are expressed by sutural features, may be emphasized by folds and very low psilate crests on
pericyst.
D e s c r i p t i o n. The dinocysts are proximate, camocavate, with a combination archeopyle of composite type pr[tA1–4]a1–3. The pericyst is rounded, with a length almost equaling its width, in the apical area forming a wide-conical horn. The endocyst is spherical. The pericoel is narrow, can be absent on the dorsal side and in the region of the intercalary plates. The periphragm is transparent, thin, easily folded, generally smooth, but can be finely granulate in the horn region. The endophragm is denser, shagreenate or finely granulate. The tabulation is of the cladopixiaceous type, expressed on the endocyst by sutural features, and emphasized by very low, smooth crests and folds on the pericyst. In the apical area, the septa become narrower; the tabulation is usually expressed by sutural features. The tabulation formula is 1pr, 4', 3a, 7'', Xc, 6''', 1p, 1''''. The cingulum and sulcus are expressed on the pericyst by very low crests and are usually emphasized by folds, and on the endocyst by sutural features.
Dimensions in μm. Holotype: pericyst length = 48, width = 37, endocyst length = 37, width = 35, pericoel width on the dorsal side = 4, length of the apical horn = 8, width = 9, height crests = 0.5–1. The mean values in 10 specimens: pericyst length = 32–55, width = 27–49, endocyst length = 26–45, width = 24–45, pericoel width on the dorsal side = 4–6, length of the apical horn = 5–9, width = 9–12, height of the crests = 0.5–1.
C o m p a r i s o n. This species is distinguished from the morphologically similar species D. cooksoniae, D. harsveldtii (Herngreen et al., 1984), D. albertii and D. tuberosum by the smoothened ornamentation of the endocyst. This feature in the new species makes its similar to D. europaeum, characterized by a smooth endocyst, although the pericoel in the latter species is considerably wider than in D. nequeas.
O c c u r r e n c e. See Fig. 1.
M a t e r i a l. 10 well-preserved specimens.