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Rhombodinium denticulatum
Rhombodinium denticulatum He Chengquan, 1991
Holotype: He Chengquan, 1991, pl.36, fig.7
Age: Middle-late Eocene
Description from He Chengquan, 1991, translated by Suning Hou, 07-01-2019
Description: The cyst is dorsal ventral flattened, the contour is like a kite or pentagonal, each corner has a fairly developed horn, except for a small antapical horn, the size of the others are similar, the edge between horn and horn is concave, serrated Shape - smooth. An apical horn, the dome is conical - cylindrical, length 27-28μm, both lateral horns length 30μm, distally thin, the end open, notched or serrated -short rod spiny; Two antapical horns are unequal, conical, distally sharp or rod-shaped, larger one 34-40μm long, smaller one 24-25μm long. Cingulum is very clear on the lateral horns. The surface of the outer wall has sparse small blunt teeth (processes), with small toothed processes at the end of each horn (especially at the lateral horns) length up to 3 μm, locally distributing in rows, but the relationship with the plates is uncertain. The inner body is round diamond shape-circular pentagon, with a pronounced convex at the lateral horns and a nearly smooth surface, occasionally with coarse grained decorations at the lateral horns and the apex edge near the archeopyle. Archeopyle intercalary, the outline is trapezoid, length larger than width, (length 35-37.5μm, width 25-27.5μm) Operculum is completely separated and preserved in situ.
Cyst length 169 - 175μm, width 153-172. 5μm, inner body length 105-110μ.m, width 100-110μm (measured 2); Holotype length 175μm, width 172.5 μm. Τ1, inner body length 110μm, width 110μm, apical horn length 27.5μm, lateral horns length 30μm, larger antapical horn length 40μm, smaller length 25μm.
Discussion This new species may be a transitional type between Rhombodinium and Wilsonidium. As the distribution of the dentate process of the outer wall is not clear or limited locally, did not form a clear polygon range, so it is better to classify it to the former genus. It is different from Rhombodinium intermedium (Cookson & Eisenack) by fairly well developed horns.
Location and stratigraphy: Wuqia County Basebulak; Wulagen fm and Basebulak fm member two and three.
Holotype: He Chengquan, 1991, pl.36, fig.7
Age: Middle-late Eocene
Description from He Chengquan, 1991, translated by Suning Hou, 07-01-2019
Description: The cyst is dorsal ventral flattened, the contour is like a kite or pentagonal, each corner has a fairly developed horn, except for a small antapical horn, the size of the others are similar, the edge between horn and horn is concave, serrated Shape - smooth. An apical horn, the dome is conical - cylindrical, length 27-28μm, both lateral horns length 30μm, distally thin, the end open, notched or serrated -short rod spiny; Two antapical horns are unequal, conical, distally sharp or rod-shaped, larger one 34-40μm long, smaller one 24-25μm long. Cingulum is very clear on the lateral horns. The surface of the outer wall has sparse small blunt teeth (processes), with small toothed processes at the end of each horn (especially at the lateral horns) length up to 3 μm, locally distributing in rows, but the relationship with the plates is uncertain. The inner body is round diamond shape-circular pentagon, with a pronounced convex at the lateral horns and a nearly smooth surface, occasionally with coarse grained decorations at the lateral horns and the apex edge near the archeopyle. Archeopyle intercalary, the outline is trapezoid, length larger than width, (length 35-37.5μm, width 25-27.5μm) Operculum is completely separated and preserved in situ.
Cyst length 169 - 175μm, width 153-172. 5μm, inner body length 105-110μ.m, width 100-110μm (measured 2); Holotype length 175μm, width 172.5 μm. Τ1, inner body length 110μm, width 110μm, apical horn length 27.5μm, lateral horns length 30μm, larger antapical horn length 40μm, smaller length 25μm.
Discussion This new species may be a transitional type between Rhombodinium and Wilsonidium. As the distribution of the dentate process of the outer wall is not clear or limited locally, did not form a clear polygon range, so it is better to classify it to the former genus. It is different from Rhombodinium intermedium (Cookson & Eisenack) by fairly well developed horns.
Location and stratigraphy: Wuqia County Basebulak; Wulagen fm and Basebulak fm member two and three.