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Cribroperidinium magnificum
Cribroperidinium magnificum Smith and Harding, 2004, p.367,371-373, pl.5, figs.1,4,7; pl.6, figs.4-6; text-fig.5.
Holotype: Smith and Harding, 2004
Age: Volgian.
Holotype: Slide U11/2, England Finder coordinates K27/2. Sedgwick Museum number X.39365 ( Plate II, 1,4,7). Paratype: SEM stub 11, grid square 2/IV, taken from sample U11. Sedgwick Museum number X.39389 ( Plate VI, 4,5).
Type locality: Gorodische section, Volga Basin.
Type horizon: Bed 6 mudstone, Dorsoplanites panderi Zone, Zaraiskites zarajskensis Subzone, Volgian.
Range: restricted to the panderi Zone, Zaraiskites zarajskensis Subzone at Gorodische, but extends up into the Craspedites subditus Zone at Kashpir (see Fig. 8).
Etymology: named after its magnificent sutural septa.
Diagnosis: slightly prolate ovoidal, proximate, acavate cribroperidinioid cyst with or without a short solid rod-like apical horn. Differentiated autophragm is densely pitted or spongy, and bears high erymnate to fenestrate or perforate sutural septa which may have smooth to undulose or highly irregular distal margins. Cingular septa are invariably higher than any others. Possesses a cribroperidinioid plate arrangement, with cingular, sulcal, first postcingular and posterior intercalary plates suppressed.
Description: Slightly axially elongate oval cyst, both episome and hyposome are dome to bell-shaped with rounded apices, and of approximately equal size (the cingulum descends slightly from dorsal to ventral surfaces, so that the hyposome is longer than the episome on the dorsal surface). Cyst proximate, acavate. Differentiated autophragm appears densely pitted and internally micro-vacuolate ( Plate VI, 5). The apex usually bears a horn, which is variably developed, being either a short solid conical structure or a slightly longer rod-like projection which tapers distally (Plate II, 1,6,9). Some specimens lack the horn altogether (Plate II, 2,8; Plate VI, 4). The autophragm bears erymnate to fenestrate sutural septa. The height of these septa is variable, but cingular septa are always the most prominent. Height of the pre- and post-cingular septa is greatest adjacent to the cingulum (7.8–12.0 μm) and in regions close to the apices. Sutural septa at the antapex tend to be higher (6.5–12.0 μm) and more elaborate than those at the apex. Distal margins of sutural septa tend to be smooth to undulose at the cingulum, but undulose to highly irregular elsewhere. Spine-like projections are often apparent at gonal areas, typically at junctions of the post-cingular plate homologues with plate 1⁗, and of the pre-cingular series with the apical plate homologues. These projections result from the fusion of sutural septa, the height of which may also be enlarged at such plate junctions.
Tabulation formula: 4′, 6″, 6c, xs, 5‴, 1p, 1⁗, with a cribroperidinioidean arrangement, showing dextral torsion and an L-type ventral arrangement (Fig. 5). The occurrence of a Cv or anterior intercalary (‘incidental’) plate(s) has not been proven.
The first and fourth (*1′ and *4′) apical plate homologues are narrow and elongate: *1′ is approximately parallel-sided, *4′ is parallel-sided adjacent to plate 6″, but broadens towards the apex. Apical plate homologues *2′ and *3′ are much reduced latitudinally in relation to the other apical homologues. Plates 1″ to 5″ are large, extending at least 3/4 of the distance between the cingulum and apex. Plate 6″ is of reduced size in comparison to the other precingular plates, and is trapezoidal to deltoidal in shape. The boundary of this plate with *1′ is small and indistinct. The archeopyle is formed from the complete loss of plate 3″, and is thus Type P. This plate is camerate, and is bordered at its anterior by plates 2′ and 3′.
The cingulum is narrow and helical, descends from posterior to anterior surfaces, and is offset at the sulcus by 2–4 cingular widths. Cingular plates have not been determined. The sulcal region is broader at the posterior end than at its anterior. The anterior part extends a short way apically above the cingular margin. Sulcal, first postcingular and posterior intercalary plate homologues are suppressed.
Postcingular plate homologues *2‴ and *6‴ are quadrate, taper towards the antapex, and are of reduced but approximately equal size. By contrast plates *3‴ to *5‴ are large and approximately triangular (very reduced junctions with antapical plate). *4‴ and *5‴ are the largest plates on the hyposome. The antapical plate homologue 1⁗ is displaced ventrally so that only the 4‴/1⁗ suture is level with the antapex.
Dimensions: length (antapex to base of horn): (60) 67 (73) μm; width at cingulum (44) 52 (60) μm; length of horn (0) 7 (12) μm. 21 specimens measured, from samples U3, U4 and U11.
Remarks: although this taxon differs from all species of Rhynchodiniopsis Deflandre emend. Jan du Chêne et al., 1985 in its cribroperidinioid tabulation (notably the ventral positioning of the antapical plate), it is superficially similar to many species of that genus. Cribroperidinium magnificum differs from R. fimbriata Duxbury emend. Jan du Chêne et al., 1985 in having an ellipsoidal rather than pentagonal outline, a much less strongly developed apical horn, and suppression of the posterior intercalary plate. C. magnificum differs from R. pennata Riley in Fisher and Riley, 1980 emend. Jan du Chêne et al., 1985 by having a short solid apical horn rather than a large conical one formed by the entire autophragm, and in having much higher and more elaborate sutural septa, particularly at the cingulum. R. martonense Bailey et al., 1997, differs from this new species in having a much more distinct and hollow apical horn and in the variable development of its sutural septa. C. magnificum is also superficially similar to Leptodinium deflandrei Riley in Fisher and Riley, 1980 emend. Lentin and Williams, 1981, but differs by the comparatively short apical horn, lack of apical cavation, possession of a differentiated autophragm, and by the development of much higher septa.
Cribroperidinium magnificum also differs from C.? perforans in possessing a more robust wall, higher and more acuminate sutural crest terminations and by lacking a perforate apical horn. Cribroperidinium sepimentum Neale and Sarjeant, 1962, differs from C. magnificum because of its prominent solid apical horn; C. boreas Davey emend. Helenes, 1984b develops a horn as an outgrowth of the cyst wall surmounted by a solid spine, and C. cornutum Davey, 1974 differs in that its very well developed horn is created by an extreme differentiation of the outer and inner part of the autophragm. C. murochoratum Dűrr 1987, whilst similar in having pronounced sutural septa and a reduced apical horn in many specimens, differs in having a very much less elongate episome, accessory sutures and striations perpendicular to the sutural septa. As defined by Sarjeant (1984), the lectotype of C. granulatum Klement emend. Stover and Evitt 1978, differs from the new taxon described here by possessing less perforate sutural septa and in having a wall layer that lacks prominent surficial subcircular pitting. C. granuligerum Klement emend. Stover and Evitt 1978 also lacks the high perforate sutural crests of C. magnificum. C. globatum Gitmez and Sarjeant emend. Helenes 1984b differs in being subcircular in ambital view. C. undoryensis sp. nov. differs from C. magnificum in lacking the same prominent solid apical horn and in having a more biconical, angular ambitus."
Holotype: Smith and Harding, 2004
Age: Volgian.
Holotype: Slide U11/2, England Finder coordinates K27/2. Sedgwick Museum number X.39365 ( Plate II, 1,4,7). Paratype: SEM stub 11, grid square 2/IV, taken from sample U11. Sedgwick Museum number X.39389 ( Plate VI, 4,5).
Type locality: Gorodische section, Volga Basin.
Type horizon: Bed 6 mudstone, Dorsoplanites panderi Zone, Zaraiskites zarajskensis Subzone, Volgian.
Range: restricted to the panderi Zone, Zaraiskites zarajskensis Subzone at Gorodische, but extends up into the Craspedites subditus Zone at Kashpir (see Fig. 8).
Etymology: named after its magnificent sutural septa.
Diagnosis: slightly prolate ovoidal, proximate, acavate cribroperidinioid cyst with or without a short solid rod-like apical horn. Differentiated autophragm is densely pitted or spongy, and bears high erymnate to fenestrate or perforate sutural septa which may have smooth to undulose or highly irregular distal margins. Cingular septa are invariably higher than any others. Possesses a cribroperidinioid plate arrangement, with cingular, sulcal, first postcingular and posterior intercalary plates suppressed.
Description: Slightly axially elongate oval cyst, both episome and hyposome are dome to bell-shaped with rounded apices, and of approximately equal size (the cingulum descends slightly from dorsal to ventral surfaces, so that the hyposome is longer than the episome on the dorsal surface). Cyst proximate, acavate. Differentiated autophragm appears densely pitted and internally micro-vacuolate ( Plate VI, 5). The apex usually bears a horn, which is variably developed, being either a short solid conical structure or a slightly longer rod-like projection which tapers distally (Plate II, 1,6,9). Some specimens lack the horn altogether (Plate II, 2,8; Plate VI, 4). The autophragm bears erymnate to fenestrate sutural septa. The height of these septa is variable, but cingular septa are always the most prominent. Height of the pre- and post-cingular septa is greatest adjacent to the cingulum (7.8–12.0 μm) and in regions close to the apices. Sutural septa at the antapex tend to be higher (6.5–12.0 μm) and more elaborate than those at the apex. Distal margins of sutural septa tend to be smooth to undulose at the cingulum, but undulose to highly irregular elsewhere. Spine-like projections are often apparent at gonal areas, typically at junctions of the post-cingular plate homologues with plate 1⁗, and of the pre-cingular series with the apical plate homologues. These projections result from the fusion of sutural septa, the height of which may also be enlarged at such plate junctions.
Tabulation formula: 4′, 6″, 6c, xs, 5‴, 1p, 1⁗, with a cribroperidinioidean arrangement, showing dextral torsion and an L-type ventral arrangement (Fig. 5). The occurrence of a Cv or anterior intercalary (‘incidental’) plate(s) has not been proven.
The first and fourth (*1′ and *4′) apical plate homologues are narrow and elongate: *1′ is approximately parallel-sided, *4′ is parallel-sided adjacent to plate 6″, but broadens towards the apex. Apical plate homologues *2′ and *3′ are much reduced latitudinally in relation to the other apical homologues. Plates 1″ to 5″ are large, extending at least 3/4 of the distance between the cingulum and apex. Plate 6″ is of reduced size in comparison to the other precingular plates, and is trapezoidal to deltoidal in shape. The boundary of this plate with *1′ is small and indistinct. The archeopyle is formed from the complete loss of plate 3″, and is thus Type P. This plate is camerate, and is bordered at its anterior by plates 2′ and 3′.
The cingulum is narrow and helical, descends from posterior to anterior surfaces, and is offset at the sulcus by 2–4 cingular widths. Cingular plates have not been determined. The sulcal region is broader at the posterior end than at its anterior. The anterior part extends a short way apically above the cingular margin. Sulcal, first postcingular and posterior intercalary plate homologues are suppressed.
Postcingular plate homologues *2‴ and *6‴ are quadrate, taper towards the antapex, and are of reduced but approximately equal size. By contrast plates *3‴ to *5‴ are large and approximately triangular (very reduced junctions with antapical plate). *4‴ and *5‴ are the largest plates on the hyposome. The antapical plate homologue 1⁗ is displaced ventrally so that only the 4‴/1⁗ suture is level with the antapex.
Dimensions: length (antapex to base of horn): (60) 67 (73) μm; width at cingulum (44) 52 (60) μm; length of horn (0) 7 (12) μm. 21 specimens measured, from samples U3, U4 and U11.
Remarks: although this taxon differs from all species of Rhynchodiniopsis Deflandre emend. Jan du Chêne et al., 1985 in its cribroperidinioid tabulation (notably the ventral positioning of the antapical plate), it is superficially similar to many species of that genus. Cribroperidinium magnificum differs from R. fimbriata Duxbury emend. Jan du Chêne et al., 1985 in having an ellipsoidal rather than pentagonal outline, a much less strongly developed apical horn, and suppression of the posterior intercalary plate. C. magnificum differs from R. pennata Riley in Fisher and Riley, 1980 emend. Jan du Chêne et al., 1985 by having a short solid apical horn rather than a large conical one formed by the entire autophragm, and in having much higher and more elaborate sutural septa, particularly at the cingulum. R. martonense Bailey et al., 1997, differs from this new species in having a much more distinct and hollow apical horn and in the variable development of its sutural septa. C. magnificum is also superficially similar to Leptodinium deflandrei Riley in Fisher and Riley, 1980 emend. Lentin and Williams, 1981, but differs by the comparatively short apical horn, lack of apical cavation, possession of a differentiated autophragm, and by the development of much higher septa.
Cribroperidinium magnificum also differs from C.? perforans in possessing a more robust wall, higher and more acuminate sutural crest terminations and by lacking a perforate apical horn. Cribroperidinium sepimentum Neale and Sarjeant, 1962, differs from C. magnificum because of its prominent solid apical horn; C. boreas Davey emend. Helenes, 1984b develops a horn as an outgrowth of the cyst wall surmounted by a solid spine, and C. cornutum Davey, 1974 differs in that its very well developed horn is created by an extreme differentiation of the outer and inner part of the autophragm. C. murochoratum Dűrr 1987, whilst similar in having pronounced sutural septa and a reduced apical horn in many specimens, differs in having a very much less elongate episome, accessory sutures and striations perpendicular to the sutural septa. As defined by Sarjeant (1984), the lectotype of C. granulatum Klement emend. Stover and Evitt 1978, differs from the new taxon described here by possessing less perforate sutural septa and in having a wall layer that lacks prominent surficial subcircular pitting. C. granuligerum Klement emend. Stover and Evitt 1978 also lacks the high perforate sutural crests of C. magnificum. C. globatum Gitmez and Sarjeant emend. Helenes 1984b differs in being subcircular in ambital view. C. undoryensis sp. nov. differs from C. magnificum in lacking the same prominent solid apical horn and in having a more biconical, angular ambitus."