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Heibergella balmei
Heibergella balmei Stover and Helby, 1987a, p.109–110, figs.7A–H. Emendation: Below, 1987a, p.126, as Hebecysta balmei.
Now Hebecysta. Originally Heibergella, subsequently (and now) Hebecysta.
Holotype: Stover and Helby, 1987a, figs.7A–B; Fensome et al., 1996, figs.1–2 — p.2061.
Locus typicus: Bonaparte Basin, Australia
Stratum typicum: Norian
Original description: Stover and Helby, 1987, p. 109-110
Cysts proximate, subspherical to ovate; when ovate apex more narrowly rounded than antapex. Autophragm thin, generally less than 1 Ám, and ornamented with low, more or less continuous, smooth ridges forming a relatively large mesh reticulum. Height and width of the muri essentially the same (generally 1 Ám or less over most of the cyst, and may be up to about 2 Ám at the poles); lumina polygonal, more or less equidimensional to elongate and from 2-10 Ám in maximum diameter. More elongate lumina near poles with longer sides aligned longitudinally, or nearly so. Archeopyle intercalary, and apparently formed by loss of one or more paraplates.
Paracingulum with 2 continuous, parallel transverse ridges marginal to it. Ends of paracingulum moderately offset. Parasulcus not indicated or may be delimited by a continuous loop-like, posteriorly closed ridge mainly on the hypocyst and extending a few microns onto the epicyst. Specimens 43(58)68 Ám in length, and 38(51)61 Ám in width.
Comment. The exact shape of the archeopyle has not been determined owing to compression, folding and tearing of the autophragm; however, the size of the opening on most specimens suggests that 2 or more paraplates are involved in archeopyle formation. Because the posterior archeopyle margin is within a few microns of the paracingulum, the narrow precingular band between archeopyle and paracingulum may be obscured by folding. On such specimens, the archeopyle may appear to be precingular. Reticulation varies not only among specimens but also on parts of individuals. Rare specimens appear almost smooth but are identified by the distinctive crenulation of the apexes. Muri may be slightly higher and lumina somewhat larger in the polar areas than on other parts of the cyst. Similarly, on some specimens, reticulation is evident on all of the cyst, whereas on others it is faintly developed adjacent to the paracingulum.
Affinities:
Stover and Helby, 1987, p. 110: Heibergella balmei differs from other species of Heibergella described by Bujak & Fisher (1976) in being reticulate: H. asymmetrica is smooth to scabrate, H. salebrosacea is densely granular and H. aculeata is spinate. Heibergella? kendelbachia is smooth to granulate and has a distinctive rhomboidal shape. A cavate form, closely resembling H. balmei, has been recorded in the H. balmei Zone.
Now Hebecysta. Originally Heibergella, subsequently (and now) Hebecysta.
Holotype: Stover and Helby, 1987a, figs.7A–B; Fensome et al., 1996, figs.1–2 — p.2061.
Locus typicus: Bonaparte Basin, Australia
Stratum typicum: Norian
Original description: Stover and Helby, 1987, p. 109-110
Cysts proximate, subspherical to ovate; when ovate apex more narrowly rounded than antapex. Autophragm thin, generally less than 1 Ám, and ornamented with low, more or less continuous, smooth ridges forming a relatively large mesh reticulum. Height and width of the muri essentially the same (generally 1 Ám or less over most of the cyst, and may be up to about 2 Ám at the poles); lumina polygonal, more or less equidimensional to elongate and from 2-10 Ám in maximum diameter. More elongate lumina near poles with longer sides aligned longitudinally, or nearly so. Archeopyle intercalary, and apparently formed by loss of one or more paraplates.
Paracingulum with 2 continuous, parallel transverse ridges marginal to it. Ends of paracingulum moderately offset. Parasulcus not indicated or may be delimited by a continuous loop-like, posteriorly closed ridge mainly on the hypocyst and extending a few microns onto the epicyst. Specimens 43(58)68 Ám in length, and 38(51)61 Ám in width.
Comment. The exact shape of the archeopyle has not been determined owing to compression, folding and tearing of the autophragm; however, the size of the opening on most specimens suggests that 2 or more paraplates are involved in archeopyle formation. Because the posterior archeopyle margin is within a few microns of the paracingulum, the narrow precingular band between archeopyle and paracingulum may be obscured by folding. On such specimens, the archeopyle may appear to be precingular. Reticulation varies not only among specimens but also on parts of individuals. Rare specimens appear almost smooth but are identified by the distinctive crenulation of the apexes. Muri may be slightly higher and lumina somewhat larger in the polar areas than on other parts of the cyst. Similarly, on some specimens, reticulation is evident on all of the cyst, whereas on others it is faintly developed adjacent to the paracingulum.
Affinities:
Stover and Helby, 1987, p. 110: Heibergella balmei differs from other species of Heibergella described by Bujak & Fisher (1976) in being reticulate: H. asymmetrica is smooth to scabrate, H. salebrosacea is densely granular and H. aculeata is spinate. Heibergella? kendelbachia is smooth to granulate and has a distinctive rhomboidal shape. A cavate form, closely resembling H. balmei, has been recorded in the H. balmei Zone.