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Glomodinium granulatum
Glomodinium granulatum (Pocock, 1972) Arhus et al., 1989
Now Evansia. Originally (and now) Evansia, subsequently Glomodinium. Lentin and Williams, 1993, retained this species in Evansia Pocock, 1972, since in they treated Glomodinium as a tax. jr. synonym of Evansia.
Holotype: Pocock, 1972, pl.24, fig.7; Jansonius, 1986, pl.5, figs.1-3, text-figs.10a-b
Locus typicus: Imperial Tidewater Wapella, Western Canada
Stratum typicum: Late Bajocian
Original description: Pocock, 1972, p.95: Evansia granulata
Vesicle dorso-ventrally flattened; outline oval with short projecting apical horn; archeopyle intercalary with simple free operculum; no plating visible; transverse and longitudinal furrows not detectable; theca two-layered comprising an inner smoothly rounded capsule about 0.5 µm thick overlain by a tightly enveloping outer granulose layer 1.0-1.5 µm thick; finely and closely granulose, giving the surface a spongy appearance; apical horn solid; about 10.0 Ám Iong; antapically a small process about 2.0 µm long formed by thickening of the outer layer; colourless; theca 58.3x40.7 µm; capsule 44.0x37.4 µm.
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Arhus et al., 1989, p. 45:
Remarks: Pocock (1972) stated that his holotype of Evansia granulata has an intercalary archeopyle with simple free operculum. Jansonius
(1986) re-examined this holotype, differentiated the angled anterior margins of 1a and 3a and concluded that three intercalary hexagonal paraplates are lost individually from the archeopyle. The present authors have observed the same intraspecific variation as Wiggins (1975), Fensome (1979) and Davies (1983) with respect to overall form, size, apicular structure and ornament in a material of more than one hundred well-preserved specimens from the Callovian cores offshore Helgeland, Norway and in Callovian out-crop samples from Kong Karls Land and Franz Josef Land and East Greenland. Coarsely sculptured forms with the shape of Jansonius's lectotype of E. evittii are fairly common particularly in Kong Karls Land.
The ornament is sometimes reduced in the cingular and sulcal regions and extensively developed in the antapical area. The overall sizes of 10
specimens fromn a sample at 14.0 m in core 3 are as follows (measurements in μm): 92 x 56, 91 x 59, 90 x 56, 89 × 57, 89 × 54, 86 x 48, 84 x 60, 83 x 51, 78 x 61, 68 x 47, respectively.
Jansonius (1986), on the basis of a small material, maintained Pocock's two pareodiniacean species as Evansia granulata and E. evittii on the grounds of a different overall habitus and a finer and more uniform ornament in E. granulata. The variation in shape and sculpture, that accord-
ing to Jansonius is interspecific variation falls within the continuous variability in our material. We therefore regard E. (G.) evittii as synonymous
with G. granulatum.
Now Evansia. Originally (and now) Evansia, subsequently Glomodinium. Lentin and Williams, 1993, retained this species in Evansia Pocock, 1972, since in they treated Glomodinium as a tax. jr. synonym of Evansia.
Holotype: Pocock, 1972, pl.24, fig.7; Jansonius, 1986, pl.5, figs.1-3, text-figs.10a-b
Locus typicus: Imperial Tidewater Wapella, Western Canada
Stratum typicum: Late Bajocian
Original description: Pocock, 1972, p.95: Evansia granulata
Vesicle dorso-ventrally flattened; outline oval with short projecting apical horn; archeopyle intercalary with simple free operculum; no plating visible; transverse and longitudinal furrows not detectable; theca two-layered comprising an inner smoothly rounded capsule about 0.5 µm thick overlain by a tightly enveloping outer granulose layer 1.0-1.5 µm thick; finely and closely granulose, giving the surface a spongy appearance; apical horn solid; about 10.0 Ám Iong; antapically a small process about 2.0 µm long formed by thickening of the outer layer; colourless; theca 58.3x40.7 µm; capsule 44.0x37.4 µm.
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Arhus et al., 1989, p. 45:
Remarks: Pocock (1972) stated that his holotype of Evansia granulata has an intercalary archeopyle with simple free operculum. Jansonius
(1986) re-examined this holotype, differentiated the angled anterior margins of 1a and 3a and concluded that three intercalary hexagonal paraplates are lost individually from the archeopyle. The present authors have observed the same intraspecific variation as Wiggins (1975), Fensome (1979) and Davies (1983) with respect to overall form, size, apicular structure and ornament in a material of more than one hundred well-preserved specimens from the Callovian cores offshore Helgeland, Norway and in Callovian out-crop samples from Kong Karls Land and Franz Josef Land and East Greenland. Coarsely sculptured forms with the shape of Jansonius's lectotype of E. evittii are fairly common particularly in Kong Karls Land.
The ornament is sometimes reduced in the cingular and sulcal regions and extensively developed in the antapical area. The overall sizes of 10
specimens fromn a sample at 14.0 m in core 3 are as follows (measurements in μm): 92 x 56, 91 x 59, 90 x 56, 89 × 57, 89 × 54, 86 x 48, 84 x 60, 83 x 51, 78 x 61, 68 x 47, respectively.
Jansonius (1986), on the basis of a small material, maintained Pocock's two pareodiniacean species as Evansia granulata and E. evittii on the grounds of a different overall habitus and a finer and more uniform ornament in E. granulata. The variation in shape and sculpture, that accord-
ing to Jansonius is interspecific variation falls within the continuous variability in our material. We therefore regard E. (G.) evittii as synonymous
with G. granulatum.