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Cribroperidinium ventriosum
From Fensome et al., 2019:
Cribroperidinium ventriosum (Wetzel, 1933a, p.161–162, pl.2, figs.4–6; text-figs.1,8) Lentin and Williams, 1973, p.35. Emendation: Lejeune-Carpentier and Sarjeant, 1981, p.5, as Cribroperidinium ventriosum. Holotype: Wetzel, 1933a, pl.2, fig.4; Lejeune-Carpentier, 1946, fig.2; Lejeune-Carpentier and Sarjeant, 1981, pl.1, figs.3–4; text-fig.3. Originally Peridinium (Appendix B), subsequently Palaeoperidinium (combination not validly published), thirdly (and now) Cribroperidinium. This combination was not validly published in Sarjeant (1967b, p.257) since that author did not fully reference the basionym. Age: Senonian.
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Emended description: [Lejeune-Carpentier and Sarjeant, 1981]:
Emended Diagnosis
Cyst rounded-pentagonal, almost as broad as long, with a short but strong, truncate apical horn. Epitract and hypotract of almost equal size ; epitract (as seen in lateral view) in the form of a truncated cone, hypotract more rounded. Low but well-marked crests, unornamented but distally irregular in form, outline the following paratabulation : 2pr, 4', 0a, 6", 7c, 6"', 1p, 2-?3"". Cingulum narrow, relatively weakly laevorotatory, divided by low ridges into paraplates ; sulcus narrow, without or only with weakly defined divisions. Surface of phragma irregularly granulate or punctate ; the precingular and postcingular paraplates are typically subdivided by accessory crests, which may constitute a penitabular simulation of the enclosing paraplate's shape or may be mere isolated ridges. Archaeopyle precingular, formed by loss of paraplate 3".
Description
The apical horn is broad based, narrows abruptly at about two-thirds length and is blunt-tipped. The flattened tip is occupied by preapical paraplate 1pr, the incurved dorsal portion of the horn by preapical paraplate 2pr, which separates paraplate 3' from the horn tip. Paraplate 1' is elongate, occupying the ventral face of the horn and the anterior prolongation of the sulcus : the two lateral flanks of apex and horn are occupied by paraplates 2' and 4'. Six large precingular paraplates are developed ; the boundary between 5" and 6" is, however, incompletely marked in the holotype. Paraplate 3", largest of the precingulars, is lost in archaeopyle formation. The cingulum is narrow and weakly laevorotatory, its two ends differing in anteroposterior position by its width or less. The first and seventh cingular paraplates are smaller than the others, which are of relatively constant size and shape. Postcingular paraplate 1"' is small and divided from the antapex by a somewhat larger posterior intercalary paraplate. The other paraplates of the postcingular series are all quite large. Both pre- and postcingular paraplates are in varying degree subdivided by accessory ridges, giving the impression of "plates within plates" so characteristic of this genus.
Davey, in his revision of Cribroperidinium (1969) specified " 0'"' (-?2'"') ", at the antapex ; Stover and Evitt (1978) however considered a single antapical paraplate to be developed. We must concur with Davey's judgement or differ from that of Stover and Evitt, for at least two, possibly three, small antapical paraplates are present in this species.
Remarks
Re-examination of the type material demonstrates that the earlier reassignment of this species to Cribroperidinium by one of us (Sarjeant, 1967b) was indeed correct. The diagnosis is emended to include a full specification of the paratabulation and statement of the style of archaeopyle ; noteworthy is the presence of two preapical paraplates, a feature several times noted in species of Gonyaulacysta but not hitherto recognised in Cribroperidinium.
Cribroperidinium ventriosum (Wetzel, 1933a, p.161–162, pl.2, figs.4–6; text-figs.1,8) Lentin and Williams, 1973, p.35. Emendation: Lejeune-Carpentier and Sarjeant, 1981, p.5, as Cribroperidinium ventriosum. Holotype: Wetzel, 1933a, pl.2, fig.4; Lejeune-Carpentier, 1946, fig.2; Lejeune-Carpentier and Sarjeant, 1981, pl.1, figs.3–4; text-fig.3. Originally Peridinium (Appendix B), subsequently Palaeoperidinium (combination not validly published), thirdly (and now) Cribroperidinium. This combination was not validly published in Sarjeant (1967b, p.257) since that author did not fully reference the basionym. Age: Senonian.
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Emended description: [Lejeune-Carpentier and Sarjeant, 1981]:
Emended Diagnosis
Cyst rounded-pentagonal, almost as broad as long, with a short but strong, truncate apical horn. Epitract and hypotract of almost equal size ; epitract (as seen in lateral view) in the form of a truncated cone, hypotract more rounded. Low but well-marked crests, unornamented but distally irregular in form, outline the following paratabulation : 2pr, 4', 0a, 6", 7c, 6"', 1p, 2-?3"". Cingulum narrow, relatively weakly laevorotatory, divided by low ridges into paraplates ; sulcus narrow, without or only with weakly defined divisions. Surface of phragma irregularly granulate or punctate ; the precingular and postcingular paraplates are typically subdivided by accessory crests, which may constitute a penitabular simulation of the enclosing paraplate's shape or may be mere isolated ridges. Archaeopyle precingular, formed by loss of paraplate 3".
Description
The apical horn is broad based, narrows abruptly at about two-thirds length and is blunt-tipped. The flattened tip is occupied by preapical paraplate 1pr, the incurved dorsal portion of the horn by preapical paraplate 2pr, which separates paraplate 3' from the horn tip. Paraplate 1' is elongate, occupying the ventral face of the horn and the anterior prolongation of the sulcus : the two lateral flanks of apex and horn are occupied by paraplates 2' and 4'. Six large precingular paraplates are developed ; the boundary between 5" and 6" is, however, incompletely marked in the holotype. Paraplate 3", largest of the precingulars, is lost in archaeopyle formation. The cingulum is narrow and weakly laevorotatory, its two ends differing in anteroposterior position by its width or less. The first and seventh cingular paraplates are smaller than the others, which are of relatively constant size and shape. Postcingular paraplate 1"' is small and divided from the antapex by a somewhat larger posterior intercalary paraplate. The other paraplates of the postcingular series are all quite large. Both pre- and postcingular paraplates are in varying degree subdivided by accessory ridges, giving the impression of "plates within plates" so characteristic of this genus.
Davey, in his revision of Cribroperidinium (1969) specified " 0'"' (-?2'"') ", at the antapex ; Stover and Evitt (1978) however considered a single antapical paraplate to be developed. We must concur with Davey's judgement or differ from that of Stover and Evitt, for at least two, possibly three, small antapical paraplates are present in this species.
Remarks
Re-examination of the type material demonstrates that the earlier reassignment of this species to Cribroperidinium by one of us (Sarjeant, 1967b) was indeed correct. The diagnosis is emended to include a full specification of the paratabulation and statement of the style of archaeopyle ; noteworthy is the presence of two preapical paraplates, a feature several times noted in species of Gonyaulacysta but not hitherto recognised in Cribroperidinium.