Back
Ovoidinium membranaceum
From Fensome et al., 2019:
Ovoidinium membranaceum Slimani, 1994, p.115–116, pl.18, figs.7–12. Holotype: Slimani, 1994, pl.18, figs.7–9. Age: early Campanian–late Maastrichtian.
---------------------------------------------------------------------------------------------------
Original description (Slimani, 1994):
Ovoidinium membranaceum sp. nov. (PI.18, Fig.7-12)
Name derivation: From the membranous appearance of the periphragm around the cyst.
Holotvpe: Halembaye sample 74, preparation 3, EF coord. M37/3.
Paratvpe: Halembaye sample 80, preparation 1, EF coord. F51/2 - F52/1.
Type locality: Halembaye sample 74.
Type horizon: Maastrichtier, upper (Lixhe Member 3).
Diagnosis: Proximate, cavitate, ovoidal to rarely subspheroidal cyst with a tiny apical horn of 2 to 6 µm; A thick-walled endocyst is irregularly separated from a fragile periphragm by a more or less continuous pericoel. The paratabulation is difficult to recognize, and is rarely indicated by folds, very fine, low ridges on the penphragm, and also by the main and accessory sutures of the archaeopyle. The archaeopyle is apical-inlercalar 4A31 with an attached or free operculum.
Dimensions: Holotype. Pericyst: length: 50 µm, width: 45 µm; endocyst: length: 45 µm, width: 40 µm. Variations: endocyst: length with operculum: 38-46 µm, length without operculum: 32-42 µm, width: 30-42 µm. Pericoel height: 1-10 µm. Number of specimens measured: 15.
Material: 41 specimens.
Description: The endophragm is dense, about 2 pm thick and finely spongy; the periphragm is thin, hyaline, fragile, chafed and often wrinkled. The pericoel generally keeps the same distance around the endocyst. The folds indicating paratabulation are relatively straighter than the rest of the periphragm folds; in the holotype, fine parasutural ridges are observable on the operculum. The archaeopyle is 21-30 µm wide with a hexagonal margin and a ventral sulcal-notch, the operculum often bears a tiny internal and an external apical protuberance. The periphragm and the endophragm are in contact on the edge of the archaeopyle.
Comparison: Ovoidinium membranaceum sp. nov. resembles O. diversum DAVEY (1979b) from the Aptian-Albian, especially in its pericoel, which is more or less developed over the entire cyst; but it is distinguished by: the ovoid shape of the cyst, its less thick endophragm, its more regular pericoel, and the presence of two tiny apical protuberances. A significant time lapse separates the two species. Craspedodinium indistinctum (COOKSON and ElSENACK, 1974) LENTIN and WILLIAMS (1976) from the Aptian-Albian shows similarities with O. membranaceum sp. nov., but it differs from it by its non-spongy endophragm, by the presence of thickenings supporting the periphragm, and by its archaeopyle, which is probably not typical of the genus Ovoidinium.
Stratigraphic distribution: Beutenaken: scales 3 to 10, Halembaye: scales 18 to 87; Upper Campanian - Upper Maastrichtian (B. mucronata Zone - B. junior Zone). Turnhout: -987 to -807.90 m, Lower Campanian - Upper Maastrichtian.
Ovoidinium membranaceum Slimani, 1994, p.115–116, pl.18, figs.7–12. Holotype: Slimani, 1994, pl.18, figs.7–9. Age: early Campanian–late Maastrichtian.
---------------------------------------------------------------------------------------------------
Original description (Slimani, 1994):
Ovoidinium membranaceum sp. nov. (PI.18, Fig.7-12)
Name derivation: From the membranous appearance of the periphragm around the cyst.
Holotvpe: Halembaye sample 74, preparation 3, EF coord. M37/3.
Paratvpe: Halembaye sample 80, preparation 1, EF coord. F51/2 - F52/1.
Type locality: Halembaye sample 74.
Type horizon: Maastrichtier, upper (Lixhe Member 3).
Diagnosis: Proximate, cavitate, ovoidal to rarely subspheroidal cyst with a tiny apical horn of 2 to 6 µm; A thick-walled endocyst is irregularly separated from a fragile periphragm by a more or less continuous pericoel. The paratabulation is difficult to recognize, and is rarely indicated by folds, very fine, low ridges on the penphragm, and also by the main and accessory sutures of the archaeopyle. The archaeopyle is apical-inlercalar 4A31 with an attached or free operculum.
Dimensions: Holotype. Pericyst: length: 50 µm, width: 45 µm; endocyst: length: 45 µm, width: 40 µm. Variations: endocyst: length with operculum: 38-46 µm, length without operculum: 32-42 µm, width: 30-42 µm. Pericoel height: 1-10 µm. Number of specimens measured: 15.
Material: 41 specimens.
Description: The endophragm is dense, about 2 pm thick and finely spongy; the periphragm is thin, hyaline, fragile, chafed and often wrinkled. The pericoel generally keeps the same distance around the endocyst. The folds indicating paratabulation are relatively straighter than the rest of the periphragm folds; in the holotype, fine parasutural ridges are observable on the operculum. The archaeopyle is 21-30 µm wide with a hexagonal margin and a ventral sulcal-notch, the operculum often bears a tiny internal and an external apical protuberance. The periphragm and the endophragm are in contact on the edge of the archaeopyle.
Comparison: Ovoidinium membranaceum sp. nov. resembles O. diversum DAVEY (1979b) from the Aptian-Albian, especially in its pericoel, which is more or less developed over the entire cyst; but it is distinguished by: the ovoid shape of the cyst, its less thick endophragm, its more regular pericoel, and the presence of two tiny apical protuberances. A significant time lapse separates the two species. Craspedodinium indistinctum (COOKSON and ElSENACK, 1974) LENTIN and WILLIAMS (1976) from the Aptian-Albian shows similarities with O. membranaceum sp. nov., but it differs from it by its non-spongy endophragm, by the presence of thickenings supporting the periphragm, and by its archaeopyle, which is probably not typical of the genus Ovoidinium.
Stratigraphic distribution: Beutenaken: scales 3 to 10, Halembaye: scales 18 to 87; Upper Campanian - Upper Maastrichtian (B. mucronata Zone - B. junior Zone). Turnhout: -987 to -807.90 m, Lower Campanian - Upper Maastrichtian.