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Leptodinium perornatum
Leptodinium perornatum Jansonius, 1986
Holotype: Jansonius, 1986, pl.3, figs.1-3, text-fig.11
Locus typicus: Tidewater Eastend Crown, W Canada
Stratum typicum: Late Bajocian
Original description: Jansonius, 1986, p.212
(Holotype) 62 x 56 µm without sculpture, cyst broadly ovoid, apex rounded, although showing some angularity at junction of paraplates, antapex broadly rounded; archeopyle precingular, 3", operculum missing; cingulum very nearly in one (equatorial) plane; paratabulation delineated by high crests, which have the same thickness and texture as the wall forming the cyst: ca 0.4-0.5µm thick, pale yellow to hyaline, minutely shagreenate-granulose surface; crests ca 5 µm tall, but 10 µm at antapex (along 1""""), scalloped to deeply scalloped so as to form an almost denticulate to spinate distal edge, the projections slightly broadened and/or bifurcate at their distal tips; the spines are flexible and easily folded over, especially the slender spines along the cingulum.
Each paraplate has a few to several (1-10) coarse, hollow granules scattered at or near its center. The cyst wall itself may be two-layered, since the hollow granules do not appear to be in communication with the interior of the cyst. The specimen is fairly well inflated (18 µm vertical distance), but still shows several large crescentic folds that simulate an inner body; however, no separate inner body is present.
The paratabulation of the ventral and apical areas is difficult to verify because they occur on the edge and are hidden by folds and crests. However, there appear to be only S precingulars (a sixth one, if present, is not delineated by a denticulate ridge against the ventral furrow). It seems that four apicals are present (and possibly one intercalary). It is a striking feature that all the major meridional precingular and postcingular crests meet at the cingulum.
Affinities:
Jansonius, 1986, p.212-213: The present form deserves to be recognized as a distinct species. It appears to be related to the form illustrated as "Endoscrinium eisenackii (Defl.) Gocht" by Davey and Riley (1978), with a Callovian-Oxfordian range, and as "Gonyaulacysta eisenackii (Defl.) Dodekova" by Sarjeant (1975), from the early Oxfordian.
It is here assigned to Leptodinium because of overall shape, the hyaline autophragm, and the striking paratabulation, in which the major meridional plate boundaries of epicyst and hypocyst line up. However, Leptodinium generally does not have spinate sutural crests. In Rhynchodiniopsis there is an apical horn, and the periphragm has a granular texture; Gonyaulacysta is clearly bicavate.
Holotype: Jansonius, 1986, pl.3, figs.1-3, text-fig.11
Locus typicus: Tidewater Eastend Crown, W Canada
Stratum typicum: Late Bajocian
Original description: Jansonius, 1986, p.212
(Holotype) 62 x 56 µm without sculpture, cyst broadly ovoid, apex rounded, although showing some angularity at junction of paraplates, antapex broadly rounded; archeopyle precingular, 3", operculum missing; cingulum very nearly in one (equatorial) plane; paratabulation delineated by high crests, which have the same thickness and texture as the wall forming the cyst: ca 0.4-0.5µm thick, pale yellow to hyaline, minutely shagreenate-granulose surface; crests ca 5 µm tall, but 10 µm at antapex (along 1""""), scalloped to deeply scalloped so as to form an almost denticulate to spinate distal edge, the projections slightly broadened and/or bifurcate at their distal tips; the spines are flexible and easily folded over, especially the slender spines along the cingulum.
Each paraplate has a few to several (1-10) coarse, hollow granules scattered at or near its center. The cyst wall itself may be two-layered, since the hollow granules do not appear to be in communication with the interior of the cyst. The specimen is fairly well inflated (18 µm vertical distance), but still shows several large crescentic folds that simulate an inner body; however, no separate inner body is present.
The paratabulation of the ventral and apical areas is difficult to verify because they occur on the edge and are hidden by folds and crests. However, there appear to be only S precingulars (a sixth one, if present, is not delineated by a denticulate ridge against the ventral furrow). It seems that four apicals are present (and possibly one intercalary). It is a striking feature that all the major meridional precingular and postcingular crests meet at the cingulum.
Affinities:
Jansonius, 1986, p.212-213: The present form deserves to be recognized as a distinct species. It appears to be related to the form illustrated as "Endoscrinium eisenackii (Defl.) Gocht" by Davey and Riley (1978), with a Callovian-Oxfordian range, and as "Gonyaulacysta eisenackii (Defl.) Dodekova" by Sarjeant (1975), from the early Oxfordian.
It is here assigned to Leptodinium because of overall shape, the hyaline autophragm, and the striking paratabulation, in which the major meridional plate boundaries of epicyst and hypocyst line up. However, Leptodinium generally does not have spinate sutural crests. In Rhynchodiniopsis there is an apical horn, and the periphragm has a granular texture; Gonyaulacysta is clearly bicavate.