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Ascodinium implanum
Ascodinium implanum, (Davey, 1979), Helenes, 1983
Now Ovoidinium. Originally (and now) Ovoidinium, subsequently Ascodinium. Lentin and Williams, 1989, retained this species in Ovoidinium Davey, 1970.
Holotype: Davey, 1979, pl.5, figs.7,11
Age: Albian
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Original description as Ovoidinium implanum: [Davey, 1979]:
Diagnosis:
A subspherical to ovoid species of Ovoidinium composed of endophragm and periphragm both of moderate thickness; the apical region is broadly subconical. The periphragm is closely adpressed to the endophragm except at the antapex where a small pericoel is usually present and at the apex where occasionally an apical pericoel exists. The periphragm is strongly ornamented and all gradations exist from coarse irregularly shaped pits (fossulate-foveolate ornamentation) to a dense, fine intraperforation. A pericingulum and antapically widening perisulcus are usually noticeable.
The combination archeopyle (type 4A31) is always developed and the operculum often remains attached.
Description:
The wall layers are each of about 0.5 µm in thickness. The endophragm appears to be smooth whereas the periphragm has a characteristically strong ornamentation and, although some positive elements may occasionally be detected around the lateral margins of the cyst, it appears most probably that a negative ornamentation is typical. The antapical periphragm extension when present, may either be almost symmetrical (see holotype) or may be more strongly developed on the left side.
Dimensions:
Holotype Range Overall length (complete specimen) 54 µm 40 (49) 56 µm Overall length (operculum detached) c. 40 µm Width 46 µm 40 (44) 48 µm Height of antapical pericoel 5 µm 0-5 µm
Remarks:
The reduced pericoels and the structure of the periphragm distinguishes O. implanum sp. nov. from all previously described species. This distinctive species only occurred in Section 62-4 where it was common
Now Ovoidinium. Originally (and now) Ovoidinium, subsequently Ascodinium. Lentin and Williams, 1989, retained this species in Ovoidinium Davey, 1970.
Holotype: Davey, 1979, pl.5, figs.7,11
Age: Albian
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Original description as Ovoidinium implanum: [Davey, 1979]:
Diagnosis:
A subspherical to ovoid species of Ovoidinium composed of endophragm and periphragm both of moderate thickness; the apical region is broadly subconical. The periphragm is closely adpressed to the endophragm except at the antapex where a small pericoel is usually present and at the apex where occasionally an apical pericoel exists. The periphragm is strongly ornamented and all gradations exist from coarse irregularly shaped pits (fossulate-foveolate ornamentation) to a dense, fine intraperforation. A pericingulum and antapically widening perisulcus are usually noticeable.
The combination archeopyle (type 4A31) is always developed and the operculum often remains attached.
Description:
The wall layers are each of about 0.5 µm in thickness. The endophragm appears to be smooth whereas the periphragm has a characteristically strong ornamentation and, although some positive elements may occasionally be detected around the lateral margins of the cyst, it appears most probably that a negative ornamentation is typical. The antapical periphragm extension when present, may either be almost symmetrical (see holotype) or may be more strongly developed on the left side.
Dimensions:
Holotype Range Overall length (complete specimen) 54 µm 40 (49) 56 µm Overall length (operculum detached) c. 40 µm Width 46 µm 40 (44) 48 µm Height of antapical pericoel 5 µm 0-5 µm
Remarks:
The reduced pericoels and the structure of the periphragm distinguishes O. implanum sp. nov. from all previously described species. This distinctive species only occurred in Section 62-4 where it was common