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Ovoidinium implanum
Ovoidinium implanum Davey, 1979
Originally (and now) Ovoidinium, subsequently Ascodinium.
Helenes, 1983, transferred this species to Ascodinium Cookson and Eisenack, 1960. Lentin and Williams, 1989, retained it in Ouoidinium.
Holotype: Davey, 1979, pl.5, figs.7,11
Age: Albian
Original description (Davey, 1979):
Ovoidinium implanum sp. nov. (Plate 5, Figures 7-9, 11, 12)
Derivation of name: Latin, implanus, uneven — with reference to the rough wall of the cyst.
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.
Holotype: MPK 1668, DSDP Leg 48, Hole 400A, Sample 62-4, 111-113 cm. Albian, northern Bay of Biscay.
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]
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.
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.
Originally (and now) Ovoidinium, subsequently Ascodinium.
Helenes, 1983, transferred this species to Ascodinium Cookson and Eisenack, 1960. Lentin and Williams, 1989, retained it in Ouoidinium.
Holotype: Davey, 1979, pl.5, figs.7,11
Age: Albian
Original description (Davey, 1979):
Ovoidinium implanum sp. nov. (Plate 5, Figures 7-9, 11, 12)
Derivation of name: Latin, implanus, uneven — with reference to the rough wall of the cyst.
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.
Holotype: MPK 1668, DSDP Leg 48, Hole 400A, Sample 62-4, 111-113 cm. Albian, northern Bay of Biscay.
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]
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.
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.