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Alterbidinium austrinum
Alterbidinium austrinum, Roncaglia and Schiøler, 1999, p. 124-125,127-128, pl.1, figs.1-9; pl.2, figs.1-6; text-figs.3A-F.
Holotype: Roncaglia and Schiøler, 1999, pl.1, figs.1-2; text-fig.3A.
Age: mid-late Campanian.
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Original description: [Roncaglia and Schiøler, 1999]:
Diagnosis:
Large, circumcavate, dorso-ventrally compressed, peridinioid cyst, with subpentagonal outline, and two lateral and two or three antapical horns. One or two projections/horns usually occur at the apex. The pericyst is thin-walled and smooth. The endocyst is located centrally, circular to subcircular in shape, smooth, and very thin-walled. The paracingulum is partially indicated on the lateral horns by short, transverse folds in the periphragm.
The archeopyle is intercalary, type I(2a), steno- to iso-deltaform; the operculum is attached posteriorly.
The paratabulation is indicated by paracingulum and archeopyle only.
Description:
Cyst large, circumcavate, dorso-ventrally compressed, subpentagonal in outline. The epicyst and hypocyst are approximately equal in size. The pericyst is smooth and thin-walled; it bears two lateral and two or three antapical horns.
Usually, one or two apical projections occur on the pericyst. The length of the apical projections is highly variable (3–38.5 μm). When single, the apical projection consists of a long (15–38.5 μm) hollow subconical horn with rounded, truncate or involute tip ( Fig. 3A, B, E); when two apical projections are present, they consist of short solid bulges (Fig. 3C, F). A wart-like 3 μm long apical structure surrounded by concentric rings occurs centrally between the bulges, on the ventral side of the cyst (Plate II, 5). In some specimens, the apex may be truncate, and apical projections absent; however, the wart-like apical structure is still present on these specimens (Fig. 3D; Plate I, 6). The left antapical horn is well developed, subconical, with acuminate, rounded or truncate termination; the right antapical horn is usually reduced in size and has a sharp to rounded termination. A third horn may occur between the left and right antapical horns, on the dorsal side of the cyst: it is shorter than the left antapical horn, hollow and with rounded or truncate termination (Fig. 3C; Plate II, 2, 4). The periphragm bears two lateral horns; they are hollow, subconical, distally rounded to truncate. Short transverse folds in the periphragm occur distally on the lateral horns. In the holotype and in a few more specimens, the left lateral horn terminates with a hook-shaped rounded tip. Generally, the left lateral horn is longer than the right [length range of the left lateral horn: 15 (24) 38 μm; length range of the right lateral horn: 11 (19) 34 μm]. A small number of specimens with only a single left lateral and left antapical horn were encountered in the studied population (Plate I, 7; Plate II, 3, 6).
The endocyst is located centrally, and is circular to subcircular in shape; it is smooth and very thin-walled, usually barely visible (Fig. 3A–F).
The paracingulum is indicated by the transverse folds in the periphragm on the two lateral horns. Generally, the parasulcus is not expressed; however, it may be indicated by an axial invagination on the lower ventral side of the periphragm.
A steno- to iso-deltaform intercalary archeopyle, type I(2a), is usually present; archeopyle index: 0.34 (0.41) 0.46. The operculum is attached posteriorly.
The paratabulation pattern is indicated by the paracingulum and archeopyle only.
Holotype: Roncaglia and Schiøler, 1999, pl.1, figs.1-2; text-fig.3A.
Age: mid-late Campanian.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Roncaglia and Schiøler, 1999]:
Diagnosis:
Large, circumcavate, dorso-ventrally compressed, peridinioid cyst, with subpentagonal outline, and two lateral and two or three antapical horns. One or two projections/horns usually occur at the apex. The pericyst is thin-walled and smooth. The endocyst is located centrally, circular to subcircular in shape, smooth, and very thin-walled. The paracingulum is partially indicated on the lateral horns by short, transverse folds in the periphragm.
The archeopyle is intercalary, type I(2a), steno- to iso-deltaform; the operculum is attached posteriorly.
The paratabulation is indicated by paracingulum and archeopyle only.
Description:
Cyst large, circumcavate, dorso-ventrally compressed, subpentagonal in outline. The epicyst and hypocyst are approximately equal in size. The pericyst is smooth and thin-walled; it bears two lateral and two or three antapical horns.
Usually, one or two apical projections occur on the pericyst. The length of the apical projections is highly variable (3–38.5 μm). When single, the apical projection consists of a long (15–38.5 μm) hollow subconical horn with rounded, truncate or involute tip ( Fig. 3A, B, E); when two apical projections are present, they consist of short solid bulges (Fig. 3C, F). A wart-like 3 μm long apical structure surrounded by concentric rings occurs centrally between the bulges, on the ventral side of the cyst (Plate II, 5). In some specimens, the apex may be truncate, and apical projections absent; however, the wart-like apical structure is still present on these specimens (Fig. 3D; Plate I, 6). The left antapical horn is well developed, subconical, with acuminate, rounded or truncate termination; the right antapical horn is usually reduced in size and has a sharp to rounded termination. A third horn may occur between the left and right antapical horns, on the dorsal side of the cyst: it is shorter than the left antapical horn, hollow and with rounded or truncate termination (Fig. 3C; Plate II, 2, 4). The periphragm bears two lateral horns; they are hollow, subconical, distally rounded to truncate. Short transverse folds in the periphragm occur distally on the lateral horns. In the holotype and in a few more specimens, the left lateral horn terminates with a hook-shaped rounded tip. Generally, the left lateral horn is longer than the right [length range of the left lateral horn: 15 (24) 38 μm; length range of the right lateral horn: 11 (19) 34 μm]. A small number of specimens with only a single left lateral and left antapical horn were encountered in the studied population (Plate I, 7; Plate II, 3, 6).
The endocyst is located centrally, and is circular to subcircular in shape; it is smooth and very thin-walled, usually barely visible (Fig. 3A–F).
The paracingulum is indicated by the transverse folds in the periphragm on the two lateral horns. Generally, the parasulcus is not expressed; however, it may be indicated by an axial invagination on the lower ventral side of the periphragm.
A steno- to iso-deltaform intercalary archeopyle, type I(2a), is usually present; archeopyle index: 0.34 (0.41) 0.46. The operculum is attached posteriorly.
The paratabulation pattern is indicated by the paracingulum and archeopyle only.