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Rhombodinium irtyschense
From Fensome et al., 2019:
Rhombodinium irtyschense (Alberti, 1961, p.8, pl.1, figs.11–12; pl.12, fig.8) Williams et al., 2015, p.311. Holotype: Alberti, 1961, pl.1, fig.12. Originally Wetzeliella, subsequently (and now) Rhombodinium. Age: Priabonian.
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Original description: [Alberti, 1961] (translated from German):
Wetzeliella (Wetzeliella) irtyschensis n. sp.
Plate 1, Figs. 11 and 12, Plate 12, Fig. 8
Holotype: The specimen preserved in preparation A 3 and shown on Plate 1, Fig. 12.
Type locality: Irtysh Valley (northern Kazakhstan, USSR).
Type strata: Lower Oligocene
Diagnosis: Carapace flat, its outline approximately rhombic, apical horn small and distinct. With two antapical horns of slightly different lengths. The lateral horns, only indicated, are notched at the tip. Transverse groove slightly indented, indicated only on the flanks of the carapace, on the middle of the front and back by two rows of spines. With an inner body closely adhering to the outer edge of the carapace. Carapace covered with very small spines, the lateral edges consequently slightly notched
Additional information: The membrane of the carapace and inner body is delicate and translucent. A rounded-rectangular to trapezoidal emergence hole lies close to the apex. The lateral edges of the carapace are often slightly curved. Its surface bears very small spines, which are blunt at their tips. Their length varies between 1 and 1.5 μm; they are slightly broadened at their base, creating a barely perceptible indentation in the lateral edges. The number of spines on the carapace is very sparse in some specimens, and in a few, spines are entirely absent. These resemble W. (Rhombodinium) draco GOCHT, but differ from it in the outline of the carapace; the two antapical horns are not as different in length as in W. (Rh.) draco Wetz. (W.) irtyschensis n.sp. thus represents a species intermediate between the subgenera W. (Wetzeliella) Etek and W. (Rhombodinium) Gocair. Of particular interest is the occurrence of a transverse groove, which otherwise only appears in W. (Rhombodinium) glabra Cooksos and in the forms of W. (Rhombodinium) draco Gocn, which occur in the Upper Cocinian of the pre-Aralsec area.
Dimensions of the holotype: length 145 μ, width 128 μ. In other specimens, the length varies between 120 μ and 140 μ, the width between 100 μ and 123 μ.
Material: 15 specimens.
Distribution: Lower Oligocene, Irtysh Valley (northern USSR).
Rhombodinium irtyschense (Alberti, 1961, p.8, pl.1, figs.11–12; pl.12, fig.8) Williams et al., 2015, p.311. Holotype: Alberti, 1961, pl.1, fig.12. Originally Wetzeliella, subsequently (and now) Rhombodinium. Age: Priabonian.
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Original description: [Alberti, 1961] (translated from German):
Wetzeliella (Wetzeliella) irtyschensis n. sp.
Plate 1, Figs. 11 and 12, Plate 12, Fig. 8
Holotype: The specimen preserved in preparation A 3 and shown on Plate 1, Fig. 12.
Type locality: Irtysh Valley (northern Kazakhstan, USSR).
Type strata: Lower Oligocene
Diagnosis: Carapace flat, its outline approximately rhombic, apical horn small and distinct. With two antapical horns of slightly different lengths. The lateral horns, only indicated, are notched at the tip. Transverse groove slightly indented, indicated only on the flanks of the carapace, on the middle of the front and back by two rows of spines. With an inner body closely adhering to the outer edge of the carapace. Carapace covered with very small spines, the lateral edges consequently slightly notched
Additional information: The membrane of the carapace and inner body is delicate and translucent. A rounded-rectangular to trapezoidal emergence hole lies close to the apex. The lateral edges of the carapace are often slightly curved. Its surface bears very small spines, which are blunt at their tips. Their length varies between 1 and 1.5 μm; they are slightly broadened at their base, creating a barely perceptible indentation in the lateral edges. The number of spines on the carapace is very sparse in some specimens, and in a few, spines are entirely absent. These resemble W. (Rhombodinium) draco GOCHT, but differ from it in the outline of the carapace; the two antapical horns are not as different in length as in W. (Rh.) draco Wetz. (W.) irtyschensis n.sp. thus represents a species intermediate between the subgenera W. (Wetzeliella) Etek and W. (Rhombodinium) Gocair. Of particular interest is the occurrence of a transverse groove, which otherwise only appears in W. (Rhombodinium) glabra Cooksos and in the forms of W. (Rhombodinium) draco Gocn, which occur in the Upper Cocinian of the pre-Aralsec area.
Dimensions of the holotype: length 145 μ, width 128 μ. In other specimens, the length varies between 120 μ and 140 μ, the width between 100 μ and 123 μ.
Material: 15 specimens.
Distribution: Lower Oligocene, Irtysh Valley (northern USSR).