Back
Epelidinium leptotoichum
Epelidinium leptotoichum Iakovleva, 2016, p.8–9 (on PDF initially published online), pl.4, figs.1–6,10–12; pl.5, figs.7–9,13; pl.5, figs.1–6,11–13; pl.6, figs.9–12; text-fig.4a (part).
Holotype: Iakovleva, 2016, pl.4, figs.1–6.
Age: earliest Eocene.
Original description (Iakovleva, 2016):
Epelidinium leptotoichum sp. nov. Plate 4, figures 1 6, 10 12; Plate 5, figures 1 6, 11 13; Plate 6, figures 9 12; Figure 4a
Synonymy. Wilsonidium? sp. A and Wilsonidium? sp. B in Iakovleva et al., 2001, pl. II, fig. 1 6; pl. III, fig. 5 8.
Holotype. Plate 4, figures 1 6; slide Sokolvsky-25-1; England Finder reference M23.
Paratype 1. Plate 5, figures 1, 2, 4, 5; slide Sokolovsky-25-1; England Finder reference O23/2.
Paratype 2. Plate 6, figures 9 12; slide Sokolovsky-25-1; England Finder reference M26/3.
Type stratum and locality. Polosataya Formation, Sokolovsky Quarry, northern Kazakhstan, sample 25; earliest Eocene.
Diagnosis. A circumcavate species of Epelidinium with a rhombic or rhombic-pentagonal outline, minimal sutural ornamentation, occasional peripheral protrusions on the periphragm and apical protrusions.
Description. A thin-walled cyst with a rhombic or rhombicpentagonal pericyst. Base of apical horn extended into a wavelike protrusion of periphragm resembling a small collar. Lateral horns are of medium size; the antapical horns are poorly developed, with the left being longer. Periphragm thin and often smooth, but sometimes slightly granulate and with occasional conical protrusions that are visible on the periphery. Endocyst is extremely thin and not always visible. Archaeopyle equiepeliform, rarely transitional to hyperepeliform (Paratype 1); operculum in place, partially attached or free.
Dimensions. Holotype: pericyst length 130 µm; pericyst width 127 µm; endocyst length 91 µm; endocyst width 101 µm. Paratype 1: pericyst length 166 µm; pericyst width 160 µm; endocyst length 108 µm; endocyst width 113 µm. Paratype 2: pericyst length 119 µm; pericyst width 116 µm. Dimensions of measured specimens: pericyst length 92-166 µm (mean value 116 µm); pericyst width 90-160 µm (mean value 113 µm); endocyst length 78-108 µm (mean value 91 µm); endocyst width 82-113 µm (mean value 92 µm). Fourteen specimens measured.
Comparison. Epelidinium leptotoichum differs from Epelidinium pechoricum, the type of the genus, in the left antapical horn being the longer and in the ornamentation. Epelidinium pechoricum has thread-like spines defining the sutures, whereas the sparse conical protrusions of Epelidinium leptotoichum only occasionally and weakly suggest sutures.
Stratigraphical range. Earliest Eocene.
Derivation of name. From the Greek leptos (thin) and to ıchos (wall) meaning the thin periphragm and endophragm.
Holotype: Iakovleva, 2016, pl.4, figs.1–6.
Age: earliest Eocene.
Original description (Iakovleva, 2016):
Epelidinium leptotoichum sp. nov. Plate 4, figures 1 6, 10 12; Plate 5, figures 1 6, 11 13; Plate 6, figures 9 12; Figure 4a
Synonymy. Wilsonidium? sp. A and Wilsonidium? sp. B in Iakovleva et al., 2001, pl. II, fig. 1 6; pl. III, fig. 5 8.
Holotype. Plate 4, figures 1 6; slide Sokolvsky-25-1; England Finder reference M23.
Paratype 1. Plate 5, figures 1, 2, 4, 5; slide Sokolovsky-25-1; England Finder reference O23/2.
Paratype 2. Plate 6, figures 9 12; slide Sokolovsky-25-1; England Finder reference M26/3.
Type stratum and locality. Polosataya Formation, Sokolovsky Quarry, northern Kazakhstan, sample 25; earliest Eocene.
Diagnosis. A circumcavate species of Epelidinium with a rhombic or rhombic-pentagonal outline, minimal sutural ornamentation, occasional peripheral protrusions on the periphragm and apical protrusions.
Description. A thin-walled cyst with a rhombic or rhombicpentagonal pericyst. Base of apical horn extended into a wavelike protrusion of periphragm resembling a small collar. Lateral horns are of medium size; the antapical horns are poorly developed, with the left being longer. Periphragm thin and often smooth, but sometimes slightly granulate and with occasional conical protrusions that are visible on the periphery. Endocyst is extremely thin and not always visible. Archaeopyle equiepeliform, rarely transitional to hyperepeliform (Paratype 1); operculum in place, partially attached or free.
Dimensions. Holotype: pericyst length 130 µm; pericyst width 127 µm; endocyst length 91 µm; endocyst width 101 µm. Paratype 1: pericyst length 166 µm; pericyst width 160 µm; endocyst length 108 µm; endocyst width 113 µm. Paratype 2: pericyst length 119 µm; pericyst width 116 µm. Dimensions of measured specimens: pericyst length 92-166 µm (mean value 116 µm); pericyst width 90-160 µm (mean value 113 µm); endocyst length 78-108 µm (mean value 91 µm); endocyst width 82-113 µm (mean value 92 µm). Fourteen specimens measured.
Comparison. Epelidinium leptotoichum differs from Epelidinium pechoricum, the type of the genus, in the left antapical horn being the longer and in the ornamentation. Epelidinium pechoricum has thread-like spines defining the sutures, whereas the sparse conical protrusions of Epelidinium leptotoichum only occasionally and weakly suggest sutures.
Stratigraphical range. Earliest Eocene.
Derivation of name. From the Greek leptos (thin) and to ıchos (wall) meaning the thin periphragm and endophragm.