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Epelidosphaeridia manifesta
From Fensome et al., 2019:
Epelidosphaeridia manifesta Nøhr-Hansen et al., 2017, p.368,370, pl.1, figs.7–16. Holotype: Nøhr-Hansen et al., 2017, pl.1, fig.7.
Age: early Cenomanian.
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Original description Nøhr-Hansen et al., 2017:
Epelidosphaeridia manifesta sp. nov., figures 7–16
Derivation of name: Latin ‘manifestus’: clear, expressed.
Holotype, figure 7, GGU sample no. 487643-3 EF F52-4.
Type locality: Section HNH081410-4, East of Fosdalen, north Hold with Hope, North-East Greenland (73°52’N, 20°43’W).
Diagnosis
A cornucavate to narrowly hypocavate species of Epelidosphaeridia. Short apical and left antapical horns; right antapical horn reduced or absent. Ornament of solid, very short, rod-like processes, mainly sutural in distribution; base of the processes sometimes coalescing into very low sutural ridges. Tabulation formula of 4’, 3a, 7’’, 5c, 5’’’, 2’’’’, of which the precingular, cingular and postcingular series are clearly marked by the processes; the intercalary series is construed from a tripartite dorsal archaeopyle suture with a wider rectilinear central portion; and the apical and antapical series are inferred from the peridiniacean affinities indicated by the other features. A bipesioid configuration is indicated by the planate anterior edge of a centrally located precingular plate 4”, and the bilaterally symmetrical arrangement of dorsal plates on the episome (epicyst). Cingulum relatively wide, faintly indented, tabulated. Sulcus centrally placed, longitudinally aligned with the central cyst axis, wide but may narrow slightly anteriorly. Archaeopyle type tAtI, wide with a weakly angulose suture. Operculum simple, free or adnate.
Description
Cysts dorsoventrally compressed, with an asymmetrical peridinioid ambitus. Apical horn short, broadly triangular, distally blunt and occasionally bearing an apical pore. Left antapical horn short, acuminate. Right antapical horn usually absent but a lobe or a rod-like process may occur in its place (e.g. , figure 15). Endocyst ambitus elliptical. The pericoels are commonly restricted to the horns’ cavities, but a narrow hypocystal pericoel may occur between the antapical horns (e.g. , figure 14). Endophragm smooth. Periphragm also smooth, bearing a moderate number of solid, short processes, mainly sutural in distribution; a variable but generally small number of intratabular process may also occur. The processes are stout, rod-like and distally simple, with buccinate, oblate or occasional capitate endings. The expanded bases of the sutural processes may coalesce, forming low, partial sutural ridges (e.g., figure 7). Most of a tabulation formula of 4’, 3a, 7’’, 5c, 5’’’, 2’’’’, Xs is commonly expressed by the sutural ornament.
The cingulum is flanked by two low, continuous or broken ridges formed by the coalescing bases of the processes. It is moderately helicoid, only slightly indented and wide relative to the overall cyst diameter. The cingular surface also bears a few sutural processes or low ridges, sometimes clearly reflecting three dorsal and two ventral cingular plates. The sulcus is defined by longitudinal periphragm folds and coalescing thickenings along its margins. It is centrally located and relatively straight, shallow and wide on the hypocyst, becoming slightly narrower and deeper on the epicyst; its surface is free of ornament.
The archaeopyle, type tAtI (1’–4’ + 1a–3a), is wide with a weakly angulose dorsal suture on which the precingular edge of three anterior intercalary plates may be distinct. The operculum is simple, free or adherent.
Dimensions
Greenland specimens:
Holotype: Pericyst length 62 µm, breadth 55 µm; endocyst length 44 µm; apical horn 8 µm; antapical horns, left 7 µm, right 3 µm; processes up to 3 µm.
Range: Pericyst length 57 (65) 76 µm, breadth 49 (56) 64 µm; endocyst length 42 (46) 52 µm; apical horn 5 (7) 10 µm; antapical horns, left 4 (7) 9 µm, right 2 (3) 3 µm; processes up to 4 µm (six specimens).
Norwegian specimens:
Range: Pericyst length 64 (71) 83 µm, breadth 49 (59) 66 µm, endocyst length 48 (58) 64 µm, apical horn 4 (8) 12 µm, antapical horns, left 5 (7) 9 µm, right 0 (2) 5 µm. Ornament up to 5 µm (11 specimens).
Distribution
Epelidosphaeridia manifesta sp. nov. has only been recorded from a narrow interval in the Lower Cenomanian; it has a first stratigraphical occurrence (FO) and last stratigraphical occurrence (LO) slightly older than the FO and LO of Ovoidinun epelidosphaeroides sp. nov.
Comparison
Epelidosphaeridia manifesta sp. nov. differs from E. spinosa in being distinctly cornucavate to weakly hypocavate, and in having a smaller number of processes, most of which are sutural, and partially developed sutural ridges. Epelidosphaeridia manifesta sp. nov. resembles, and appears to grade morphologically into, Ovoidinium epelidosphaeroides sp. nov. specimens with few sutural processes (e.g., figures 13–16), from which it differs in its reduced pericoel width and more numerous processes, and in lacking a cingular flange. There appears to be a continuous morphological transition between Epelidosphaeridia sp. 1 of Nøhr-Hansen Citation1993, E. spinosa, E. manifesta sp. nov. and Ovoidinium epelidosphaeroides sp. nov.
Epelidosphaeridia manifesta Nøhr-Hansen et al., 2017, p.368,370, pl.1, figs.7–16. Holotype: Nøhr-Hansen et al., 2017, pl.1, fig.7.
Age: early Cenomanian.
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Original description Nøhr-Hansen et al., 2017:
Epelidosphaeridia manifesta sp. nov., figures 7–16
Derivation of name: Latin ‘manifestus’: clear, expressed.
Holotype, figure 7, GGU sample no. 487643-3 EF F52-4.
Type locality: Section HNH081410-4, East of Fosdalen, north Hold with Hope, North-East Greenland (73°52’N, 20°43’W).
Diagnosis
A cornucavate to narrowly hypocavate species of Epelidosphaeridia. Short apical and left antapical horns; right antapical horn reduced or absent. Ornament of solid, very short, rod-like processes, mainly sutural in distribution; base of the processes sometimes coalescing into very low sutural ridges. Tabulation formula of 4’, 3a, 7’’, 5c, 5’’’, 2’’’’, of which the precingular, cingular and postcingular series are clearly marked by the processes; the intercalary series is construed from a tripartite dorsal archaeopyle suture with a wider rectilinear central portion; and the apical and antapical series are inferred from the peridiniacean affinities indicated by the other features. A bipesioid configuration is indicated by the planate anterior edge of a centrally located precingular plate 4”, and the bilaterally symmetrical arrangement of dorsal plates on the episome (epicyst). Cingulum relatively wide, faintly indented, tabulated. Sulcus centrally placed, longitudinally aligned with the central cyst axis, wide but may narrow slightly anteriorly. Archaeopyle type tAtI, wide with a weakly angulose suture. Operculum simple, free or adnate.
Description
Cysts dorsoventrally compressed, with an asymmetrical peridinioid ambitus. Apical horn short, broadly triangular, distally blunt and occasionally bearing an apical pore. Left antapical horn short, acuminate. Right antapical horn usually absent but a lobe or a rod-like process may occur in its place (e.g. , figure 15). Endocyst ambitus elliptical. The pericoels are commonly restricted to the horns’ cavities, but a narrow hypocystal pericoel may occur between the antapical horns (e.g. , figure 14). Endophragm smooth. Periphragm also smooth, bearing a moderate number of solid, short processes, mainly sutural in distribution; a variable but generally small number of intratabular process may also occur. The processes are stout, rod-like and distally simple, with buccinate, oblate or occasional capitate endings. The expanded bases of the sutural processes may coalesce, forming low, partial sutural ridges (e.g., figure 7). Most of a tabulation formula of 4’, 3a, 7’’, 5c, 5’’’, 2’’’’, Xs is commonly expressed by the sutural ornament.
The cingulum is flanked by two low, continuous or broken ridges formed by the coalescing bases of the processes. It is moderately helicoid, only slightly indented and wide relative to the overall cyst diameter. The cingular surface also bears a few sutural processes or low ridges, sometimes clearly reflecting three dorsal and two ventral cingular plates. The sulcus is defined by longitudinal periphragm folds and coalescing thickenings along its margins. It is centrally located and relatively straight, shallow and wide on the hypocyst, becoming slightly narrower and deeper on the epicyst; its surface is free of ornament.
The archaeopyle, type tAtI (1’–4’ + 1a–3a), is wide with a weakly angulose dorsal suture on which the precingular edge of three anterior intercalary plates may be distinct. The operculum is simple, free or adherent.
Dimensions
Greenland specimens:
Holotype: Pericyst length 62 µm, breadth 55 µm; endocyst length 44 µm; apical horn 8 µm; antapical horns, left 7 µm, right 3 µm; processes up to 3 µm.
Range: Pericyst length 57 (65) 76 µm, breadth 49 (56) 64 µm; endocyst length 42 (46) 52 µm; apical horn 5 (7) 10 µm; antapical horns, left 4 (7) 9 µm, right 2 (3) 3 µm; processes up to 4 µm (six specimens).
Norwegian specimens:
Range: Pericyst length 64 (71) 83 µm, breadth 49 (59) 66 µm, endocyst length 48 (58) 64 µm, apical horn 4 (8) 12 µm, antapical horns, left 5 (7) 9 µm, right 0 (2) 5 µm. Ornament up to 5 µm (11 specimens).
Distribution
Epelidosphaeridia manifesta sp. nov. has only been recorded from a narrow interval in the Lower Cenomanian; it has a first stratigraphical occurrence (FO) and last stratigraphical occurrence (LO) slightly older than the FO and LO of Ovoidinun epelidosphaeroides sp. nov.
Comparison
Epelidosphaeridia manifesta sp. nov. differs from E. spinosa in being distinctly cornucavate to weakly hypocavate, and in having a smaller number of processes, most of which are sutural, and partially developed sutural ridges. Epelidosphaeridia manifesta sp. nov. resembles, and appears to grade morphologically into, Ovoidinium epelidosphaeroides sp. nov. specimens with few sutural processes (e.g., figures 13–16), from which it differs in its reduced pericoel width and more numerous processes, and in lacking a cingular flange. There appears to be a continuous morphological transition between Epelidosphaeridia sp. 1 of Nøhr-Hansen Citation1993, E. spinosa, E. manifesta sp. nov. and Ovoidinium epelidosphaeroides sp. nov.