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Alterbidinium ambiguum
From Fensome et al., 2019:
Alterbidinium ambiguum, (He Chengquan, 1991, p.72–73, pl.29, figs.1–6) Lentin and Williams, 1993, p.21.
Holotype: He Chengquan, 1991, pl.29, fig.3.
Originally Alterbia (generic name illegitimate), subsequently (and now) Alterbidinium.
Age: Cenomanian–Middle Eocene
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Original description: [He Chengquan, 1991]: (translated by Suning Hou, 07-01-2019):
Description:
The cyst is dorsal-ventral flattened, outline elongated pentagonal, divided into nearly two equal part by the cingulum.
Epicyst conical, edges straight or slightly convex, with a short apical horn, papillary, top usually concave;
Hypocyst inverted trapezoidal, two antapical horns are degenerated to varying degrees, one is more obvious, blunt conical, 3 -4.5μm long, another is convex or wide circle.
The cingulum is in the equatorial position, shallow flat, annular, width 6-7.5μm, its edges are decorated with fine ridges, often with particles on the ridges.
The sulcus limited to the hypocyst, sometimes missing.
The surface of the outer wall is granulate, some of the particles are weak, slightly shown in the contour, and on some specimen particles are developed locally, sticking out of the contour line.
The outline of the inner body is ovoid, usually blunted (due to corrosion), perhaps wrinkles; It is widely spaced from the outer wall.
When the archeopyle exists, intercalary, trapezoid, height larger than width, formed by the movement of a piece of the intercalary plate made. Operculum preserved in situ.
Dimensions:
Cyst length 56-62μm, width 45-47.5 μm, inner body length 38-42μm, width 35 μm (measured 6 specimens);
The holotype length 60μm, width 45μm, inner body length 38μm, width 35μm, cingulum width 7.5μm, a antapical horn length 4μm.
Affinities/Discussion:
The inner body is often obscure to determine its taxonomy, which may be related to the thinning and corrosion of the inner body. In the well-preserved specimens (such as the holotype), the inner body is clearer.) The new species is physically similar to Alterbia psilata (Yu et Zhang) comb. Nov. (YU Jingxian et al., 1980, page 108, plates2, figure 19), but the inner body of the latter is obviously elongated.
Alterbidinium ambiguum, (He Chengquan, 1991, p.72–73, pl.29, figs.1–6) Lentin and Williams, 1993, p.21.
Holotype: He Chengquan, 1991, pl.29, fig.3.
Originally Alterbia (generic name illegitimate), subsequently (and now) Alterbidinium.
Age: Cenomanian–Middle Eocene
---------------------------------------------------------------------------------------------------
Original description: [He Chengquan, 1991]: (translated by Suning Hou, 07-01-2019):
Description:
The cyst is dorsal-ventral flattened, outline elongated pentagonal, divided into nearly two equal part by the cingulum.
Epicyst conical, edges straight or slightly convex, with a short apical horn, papillary, top usually concave;
Hypocyst inverted trapezoidal, two antapical horns are degenerated to varying degrees, one is more obvious, blunt conical, 3 -4.5μm long, another is convex or wide circle.
The cingulum is in the equatorial position, shallow flat, annular, width 6-7.5μm, its edges are decorated with fine ridges, often with particles on the ridges.
The sulcus limited to the hypocyst, sometimes missing.
The surface of the outer wall is granulate, some of the particles are weak, slightly shown in the contour, and on some specimen particles are developed locally, sticking out of the contour line.
The outline of the inner body is ovoid, usually blunted (due to corrosion), perhaps wrinkles; It is widely spaced from the outer wall.
When the archeopyle exists, intercalary, trapezoid, height larger than width, formed by the movement of a piece of the intercalary plate made. Operculum preserved in situ.
Dimensions:
Cyst length 56-62μm, width 45-47.5 μm, inner body length 38-42μm, width 35 μm (measured 6 specimens);
The holotype length 60μm, width 45μm, inner body length 38μm, width 35μm, cingulum width 7.5μm, a antapical horn length 4μm.
Affinities/Discussion:
The inner body is often obscure to determine its taxonomy, which may be related to the thinning and corrosion of the inner body. In the well-preserved specimens (such as the holotype), the inner body is clearer.) The new species is physically similar to Alterbia psilata (Yu et Zhang) comb. Nov. (YU Jingxian et al., 1980, page 108, plates2, figure 19), but the inner body of the latter is obviously elongated.