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Cyclonephelium bulbosum
Cyclonephelium bulbosum Smith and Harding, 2004, p.375-376, pl.4, figs.6-10; pl.5, figs.4-6; text-fig.7.
Questionable assignment: Smith and Harding (2004, p.375).
Holotype: Smith and Harding, 2004, pl.4, figs.6-8.
Age: Early Valanginian.
Holotype: Slide K17/0-5, England Finder coordinates K30/3. Sedgwick Museum number X.39375 ( Plate IV, 6–8). Paratype: Slide K17/0-10/2, England Finder coordinates N38. Sedgwick Museum number X.39376 ( Plate IV, 9,10). Type locality: Kashpir section, Volga Basin. Type horizon: Bed 24 (sample K17), sandstone with phosphate concretions, Lower Valanginian. Range: only recorded from the type horizon (see Fig. 8).
Etymology: named after the laterally bulbous hyposome and flattened antapical region, which is atypical of the genus.
Diagnosis: proximochorate acavate cyst with a dome-shaped apex, and usually flattened or very slightly bilobed antapex. Hyposome much longer and wider than episome. The autophragm bears short solid rod-like projections with expanded terminations, which may be discrete or branching/anastomosing/fused, and are concentrated in marginal and apical regions. The complex archeopyle involves all of the apical plate homologues as a simple polyplacoid operculum which remains adnate via plates 6″, as, and 1″, and also plate 3″ which remains adnate via its boundary with the cingulum. Archeopyle formula: (tA)aP3″a.
Description: variable shape, prominent dorso-ventral compression with the apex usually rounded and dome-shaped, the antapex occasionally rounded ( Plate V, 6), but usually flattened (Plate IV, 6,7) or bulging/laterally lobate (Plate IV, 9,10) rather than antapically lobate, and therefore somewhat atypical for the genus. The position of the cingulum is often indicated by a slight or occasionally pronounced restriction of the cyst ambitus (Plate IV, 9). Hyposome is markedly longer and wider than the episome. Cyst is proximochorate, acavate, with greatest concentration of processes in marginal and apical regions, and general absence of processes in mid-dorsal, and mid-ventral regions. Processes are short and solid with expanded terminations, and may be discrete, fused or branched distally to form process-clusters. A small but distinct tuft of slightly longer processes is usually present in the middle of the antapex, between the lobes in bilobed specimens. Autophragm is thin and smooth in mid-dorsal and mid-ventral areas. Tabulation is not expressed by sutural features on the cyst surface, and is only apparent at the archeopyle margin. However, the dome-shaped nature of the apex often precludes examination of archeopyle character in many specimens, since the operculum is adnate and remains in its original position following excystment. Neverthless, the apical series clearly forms the majority of the operculum. Both the shape of the operculum and the width of the opercular attachment on the ventral surface suggest that plate homologues *4′; *1′; and *2′ remain attached at their boundaries with plates 6″, as and 1″ respectively (Fig. 7). The morphology of the operculum would indicate that the sulcus is offset to the left. This is supported by the position and number of accessory archeopyle sutures between precingular plates. Plate 3″ is identified in a mid-dorsal position by particularly deep accessory archeopyle sutures, which appear to extend to the cingulum, and is thus a second adnate part of the operculum. The archeopyle formula is thus (tA)aP3″a, atypical for the genus.
Dimensions: antapical-apical length: (47) 59 (66) μm; maximum width: (53) 59 (69) μm. 19 specimens measured, all from sample K17.
Remarks: this species is tentatively placed in the genus Cyclonephelium due to the restriction of processes to marginal and apical regions typical of that genus. However, although the operculum may remain attached in many examples of Cyclonephelium, it is not typically adnate, and generally does not have such deep accessory sutures separating plate 3″ from its neighbours. This archeopyle type is thus considered atypical of the genus, as is the ambital outline of the hyposome, which is much more laterally lobate (more akin to the morphological end-members of the leptodinioid Sirmiodinium grossi) rather than the typical antapically directed lobes of other Cyclonephelium species. Thus the archeopyle and ambital outline serve to differentiate this new taxon from all other members of the genus, and from those superficially similar genera such as Circulodinium Alberti 1961, Batiacasphaera Drugg emend. Dörhöfer and Davies 1980, Kallosphaeridium de Coninck emend. Jan du Chêne et al., 1985a and Sentusidinium Sarjeant and Stover emend. Courtinat 1989.
Questionable assignment: Smith and Harding (2004, p.375).
Holotype: Smith and Harding, 2004, pl.4, figs.6-8.
Age: Early Valanginian.
Holotype: Slide K17/0-5, England Finder coordinates K30/3. Sedgwick Museum number X.39375 ( Plate IV, 6–8). Paratype: Slide K17/0-10/2, England Finder coordinates N38. Sedgwick Museum number X.39376 ( Plate IV, 9,10). Type locality: Kashpir section, Volga Basin. Type horizon: Bed 24 (sample K17), sandstone with phosphate concretions, Lower Valanginian. Range: only recorded from the type horizon (see Fig. 8).
Etymology: named after the laterally bulbous hyposome and flattened antapical region, which is atypical of the genus.
Diagnosis: proximochorate acavate cyst with a dome-shaped apex, and usually flattened or very slightly bilobed antapex. Hyposome much longer and wider than episome. The autophragm bears short solid rod-like projections with expanded terminations, which may be discrete or branching/anastomosing/fused, and are concentrated in marginal and apical regions. The complex archeopyle involves all of the apical plate homologues as a simple polyplacoid operculum which remains adnate via plates 6″, as, and 1″, and also plate 3″ which remains adnate via its boundary with the cingulum. Archeopyle formula: (tA)aP3″a.
Description: variable shape, prominent dorso-ventral compression with the apex usually rounded and dome-shaped, the antapex occasionally rounded ( Plate V, 6), but usually flattened (Plate IV, 6,7) or bulging/laterally lobate (Plate IV, 9,10) rather than antapically lobate, and therefore somewhat atypical for the genus. The position of the cingulum is often indicated by a slight or occasionally pronounced restriction of the cyst ambitus (Plate IV, 9). Hyposome is markedly longer and wider than the episome. Cyst is proximochorate, acavate, with greatest concentration of processes in marginal and apical regions, and general absence of processes in mid-dorsal, and mid-ventral regions. Processes are short and solid with expanded terminations, and may be discrete, fused or branched distally to form process-clusters. A small but distinct tuft of slightly longer processes is usually present in the middle of the antapex, between the lobes in bilobed specimens. Autophragm is thin and smooth in mid-dorsal and mid-ventral areas. Tabulation is not expressed by sutural features on the cyst surface, and is only apparent at the archeopyle margin. However, the dome-shaped nature of the apex often precludes examination of archeopyle character in many specimens, since the operculum is adnate and remains in its original position following excystment. Neverthless, the apical series clearly forms the majority of the operculum. Both the shape of the operculum and the width of the opercular attachment on the ventral surface suggest that plate homologues *4′; *1′; and *2′ remain attached at their boundaries with plates 6″, as and 1″ respectively (Fig. 7). The morphology of the operculum would indicate that the sulcus is offset to the left. This is supported by the position and number of accessory archeopyle sutures between precingular plates. Plate 3″ is identified in a mid-dorsal position by particularly deep accessory archeopyle sutures, which appear to extend to the cingulum, and is thus a second adnate part of the operculum. The archeopyle formula is thus (tA)aP3″a, atypical for the genus.
Dimensions: antapical-apical length: (47) 59 (66) μm; maximum width: (53) 59 (69) μm. 19 specimens measured, all from sample K17.
Remarks: this species is tentatively placed in the genus Cyclonephelium due to the restriction of processes to marginal and apical regions typical of that genus. However, although the operculum may remain attached in many examples of Cyclonephelium, it is not typically adnate, and generally does not have such deep accessory sutures separating plate 3″ from its neighbours. This archeopyle type is thus considered atypical of the genus, as is the ambital outline of the hyposome, which is much more laterally lobate (more akin to the morphological end-members of the leptodinioid Sirmiodinium grossi) rather than the typical antapically directed lobes of other Cyclonephelium species. Thus the archeopyle and ambital outline serve to differentiate this new taxon from all other members of the genus, and from those superficially similar genera such as Circulodinium Alberti 1961, Batiacasphaera Drugg emend. Dörhöfer and Davies 1980, Kallosphaeridium de Coninck emend. Jan du Chêne et al., 1985a and Sentusidinium Sarjeant and Stover emend. Courtinat 1989.