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Alterbidinium biaperturum
From Fensome et al., 2019:
Alterbidinium biaperturum, (McIntyre, 1975, p.66, pl.3, figs.5–8) Fensome et al., 2016b, p.25.
Holotype: McIntyre, 1975, pl.3, figs.5–6.
Originally Deflandrea, subsequently Chatangiella?, thirdly (and now) Alterbidinium.
Age: Campanian–Maastrichtian.
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Original description as Deflandrea biapertura: [McIntyre, 1975, p. 66]:
Deflandrea biapertura sp. nov.
Plate 3, figures 5-8
Holotype: Plate 3, fig. 5, 6, G.S.C. No. 38020, Slide 12652/5, coordinates 114 x 1175.
Holotype locality and stratum: Horton River, N.W.T., Section CR16B, 180-190 feet from base of section, "Pale shale zone," Maastrichtian, (lat. 69°28' N, long. 126°58 W).
Description: Cyst cavate, dorsoventrally flattened, more or less spherical in dorsoventral view except for apical and antapical horns, and is divided into equal epitract and hypotract by a simple cingulum. Apical horn 10-30 μm long and usually rounded at the end. Left antapical horn 15-30 μm long, narrow, and pointed; right antapical horn normally appears only as an angular bulge. Cingulum about 7 μm wide and bordered on both edges by slightly raised irregular ridges. A large wide sulcus is present on the ventral surface. The large intercalary (2a) archeopyle is rounded hexagonal and the operculum is often attached at the posterior margin. There is no sign of an archeopyle in the endoblast. A large
circular opening (antapical archeopyle?) is usually present in the periblast between the antapical horns (PI. 3, fig. 5, 6). Endoblast large, spherical, normally not folded, and usually closely appressed to periblast laterally, especially in hypotract. Apical and antapical pericoels are present. Endophragm about 1 μm thick and finely scabrate to finely granulate, especially on anterior and posterior ends. Periphragm less than 1 μm thick and smooth to finely scabrate. It is often wrinkled and has a somewhat striate appearance (PI. 3, fig. 7).
Size: Holotype, 136 μm long, 78 μm wide; endoblast, 60 μm long; range, 94-145 μm long, 60-92 μm wide; endoblast 41-78 μm long.
Name derivation: The name refers to the 2 openings -- the intercalary archeopyle and the opening at the antapex.
Remarks: D. biapertura is abundant in Division H3 in Section CR16B and is recorded as D. sp. 5 in Mclntyre (1974). A similar form was illustrated by Wilson (1971) as Deflandrea aff. sverdrupiana. D. biapertura is similar to D. sverdrupiana in shape and also possesses a relatively large endoblast, but it is larger and lacks the tabulation features of D. sverdrupiana. D. magna Davey (1970) has a tapering epitract and less well-developed apical and antapical horns. Apparently it also has a smooth endoblast, and the cyst is smaller than that of D. biapertura. There appear to be no other species of Deflandrea known that have the antapical opening typical of D. biapertura. An antapical opening with an attached operculum has been noted in Ovoidinium ostium by Davey (1970).
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Remarks by Fensome et al., 2016b (transfer to Alterbidinium):
Remarks. This species is distinguished by an opening in the pericyst between the antapical horns. From the illustrations of the holotype in McIntyre (1975, plate 3, figs5, 6), Alterbidinium (as Chatangiella?) biaperturum appears to possess a cingulum delineated by continuous ridges; the periarchaeopyle is extremely unusual, being distinctly deltaform on one lateral margin but, as M. Pearce (personal communication 2015) has noted, possibly thetaform on the other lateral margin. Whether such asymmetry occurs in other specimens of this species is unknown. But regardless, the species is thus not assignable to Chatangiella. Lentin & Williams (1976) were aware of these differences when provisionally including this taxon in Chatangiella, but did not consider assigning it to Alterbidinium. We herein transfer the species to Alterbidinium to more accurately reflect its morphology.
Alterbidinium biaperturum, (McIntyre, 1975, p.66, pl.3, figs.5–8) Fensome et al., 2016b, p.25.
Holotype: McIntyre, 1975, pl.3, figs.5–6.
Originally Deflandrea, subsequently Chatangiella?, thirdly (and now) Alterbidinium.
Age: Campanian–Maastrichtian.
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Original description as Deflandrea biapertura: [McIntyre, 1975, p. 66]:
Deflandrea biapertura sp. nov.
Plate 3, figures 5-8
Holotype: Plate 3, fig. 5, 6, G.S.C. No. 38020, Slide 12652/5, coordinates 114 x 1175.
Holotype locality and stratum: Horton River, N.W.T., Section CR16B, 180-190 feet from base of section, "Pale shale zone," Maastrichtian, (lat. 69°28' N, long. 126°58 W).
Description: Cyst cavate, dorsoventrally flattened, more or less spherical in dorsoventral view except for apical and antapical horns, and is divided into equal epitract and hypotract by a simple cingulum. Apical horn 10-30 μm long and usually rounded at the end. Left antapical horn 15-30 μm long, narrow, and pointed; right antapical horn normally appears only as an angular bulge. Cingulum about 7 μm wide and bordered on both edges by slightly raised irregular ridges. A large wide sulcus is present on the ventral surface. The large intercalary (2a) archeopyle is rounded hexagonal and the operculum is often attached at the posterior margin. There is no sign of an archeopyle in the endoblast. A large
circular opening (antapical archeopyle?) is usually present in the periblast between the antapical horns (PI. 3, fig. 5, 6). Endoblast large, spherical, normally not folded, and usually closely appressed to periblast laterally, especially in hypotract. Apical and antapical pericoels are present. Endophragm about 1 μm thick and finely scabrate to finely granulate, especially on anterior and posterior ends. Periphragm less than 1 μm thick and smooth to finely scabrate. It is often wrinkled and has a somewhat striate appearance (PI. 3, fig. 7).
Size: Holotype, 136 μm long, 78 μm wide; endoblast, 60 μm long; range, 94-145 μm long, 60-92 μm wide; endoblast 41-78 μm long.
Name derivation: The name refers to the 2 openings -- the intercalary archeopyle and the opening at the antapex.
Remarks: D. biapertura is abundant in Division H3 in Section CR16B and is recorded as D. sp. 5 in Mclntyre (1974). A similar form was illustrated by Wilson (1971) as Deflandrea aff. sverdrupiana. D. biapertura is similar to D. sverdrupiana in shape and also possesses a relatively large endoblast, but it is larger and lacks the tabulation features of D. sverdrupiana. D. magna Davey (1970) has a tapering epitract and less well-developed apical and antapical horns. Apparently it also has a smooth endoblast, and the cyst is smaller than that of D. biapertura. There appear to be no other species of Deflandrea known that have the antapical opening typical of D. biapertura. An antapical opening with an attached operculum has been noted in Ovoidinium ostium by Davey (1970).
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Remarks by Fensome et al., 2016b (transfer to Alterbidinium):
Remarks. This species is distinguished by an opening in the pericyst between the antapical horns. From the illustrations of the holotype in McIntyre (1975, plate 3, figs5, 6), Alterbidinium (as Chatangiella?) biaperturum appears to possess a cingulum delineated by continuous ridges; the periarchaeopyle is extremely unusual, being distinctly deltaform on one lateral margin but, as M. Pearce (personal communication 2015) has noted, possibly thetaform on the other lateral margin. Whether such asymmetry occurs in other specimens of this species is unknown. But regardless, the species is thus not assignable to Chatangiella. Lentin & Williams (1976) were aware of these differences when provisionally including this taxon in Chatangiella, but did not consider assigning it to Alterbidinium. We herein transfer the species to Alterbidinium to more accurately reflect its morphology.