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Leptodinium simplex
From Fensome et al., 2019:
Leptodinium simplex Burger, 1980a, p.84, pl.42, figs.1–5. Holotype: Burger, 1980a, pl.42, figs.4a–b; Jan du Chêne et al., 1986a, pl.75, fig.10. Questionable assignment: Sarjeant (1982b, p.38) — however, Jan du Chêne et al. (1986a, p.210) included the species in Leptodinium without question. Age: Aptian.
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Original description: [Burger, 1980]:
Leptodinium simplex sp. nov
cf. Pl. 41, fig. 4; PI. 42, figs. 1-5
Holotype: BMR Roma 8, depth 31.1 m (102 ft 2 in); Wallumbilla Formation. Doncaster Member. Cretaceous, late Aptian (MFP 4676-2, 432/ 1027; CPC 16425. Pl. 42, fig. 4).
Description: Cyst spherical to roundly ellipsoidal, tabulated, without horns. Paracingulum and parasulcus well defined; cingulum slightly helicoid, height of paracingular plates 4-7 um; sulcal area may be composed of several paraplates. Plates bordered by thin, psilate, smoothly crested lists 4-10 um high, Archaeopyle large, triangular, with a broad or narrow base, formed by dislodgement of paraplate 3". Wall thin, psilate to punctate.
Dimensions: Overall length of 15 specimens 45-70 μm, width 44-60 μm.
Distribution: A frequently occurring species in the marine sequence of the Surat Basin. Tralau (1972) reported similar specimens as Leptodinium sp. (his fig. 7) from the Late Cretaceous of Sweden.
Comments: The species is distinguished by its spherical shape, psilate cyst wall and regular, symmetrical paratabulation. In some specimens the parasutural lists are higher in the antapical region. L. simplex sp. nov. is smaller than L. eumorphum (Cookson & Eisenack, 1960b) Eisenack, 1961, and Pterodinium cornutum Cookson & Bisenack, 1962b. It is similar to the type species L. Subtile Klement, but the paracingulum appears to divide the cyst into two more symmetrical portions. It is also close to Leptodinium modicum Brideaux & Mclntyre, 1975, from the middle Albian of Horton River, Canada, but has a less helicoidal paracingulum, higher parasutural lists, and a less a sinuous (almost straight) parasulcus. In these respects it is closer to Pterodinium sp. A (see Brideaux & McIntyre, p. 31, pl. 9, fig. 9).
The Surat Basin specimens resemble those from the upper Tertiary of Victoria which Deflandre & Cookson (1955) identified with Spiniferites cingulatus (O. Wetzel ) and described as having no processes.
Leptodinium simplex Burger, 1980a, p.84, pl.42, figs.1–5. Holotype: Burger, 1980a, pl.42, figs.4a–b; Jan du Chêne et al., 1986a, pl.75, fig.10. Questionable assignment: Sarjeant (1982b, p.38) — however, Jan du Chêne et al. (1986a, p.210) included the species in Leptodinium without question. Age: Aptian.
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Original description: [Burger, 1980]:
Leptodinium simplex sp. nov
cf. Pl. 41, fig. 4; PI. 42, figs. 1-5
Holotype: BMR Roma 8, depth 31.1 m (102 ft 2 in); Wallumbilla Formation. Doncaster Member. Cretaceous, late Aptian (MFP 4676-2, 432/ 1027; CPC 16425. Pl. 42, fig. 4).
Description: Cyst spherical to roundly ellipsoidal, tabulated, without horns. Paracingulum and parasulcus well defined; cingulum slightly helicoid, height of paracingular plates 4-7 um; sulcal area may be composed of several paraplates. Plates bordered by thin, psilate, smoothly crested lists 4-10 um high, Archaeopyle large, triangular, with a broad or narrow base, formed by dislodgement of paraplate 3". Wall thin, psilate to punctate.
Dimensions: Overall length of 15 specimens 45-70 μm, width 44-60 μm.
Distribution: A frequently occurring species in the marine sequence of the Surat Basin. Tralau (1972) reported similar specimens as Leptodinium sp. (his fig. 7) from the Late Cretaceous of Sweden.
Comments: The species is distinguished by its spherical shape, psilate cyst wall and regular, symmetrical paratabulation. In some specimens the parasutural lists are higher in the antapical region. L. simplex sp. nov. is smaller than L. eumorphum (Cookson & Eisenack, 1960b) Eisenack, 1961, and Pterodinium cornutum Cookson & Bisenack, 1962b. It is similar to the type species L. Subtile Klement, but the paracingulum appears to divide the cyst into two more symmetrical portions. It is also close to Leptodinium modicum Brideaux & Mclntyre, 1975, from the middle Albian of Horton River, Canada, but has a less helicoidal paracingulum, higher parasutural lists, and a less a sinuous (almost straight) parasulcus. In these respects it is closer to Pterodinium sp. A (see Brideaux & McIntyre, p. 31, pl. 9, fig. 9).
The Surat Basin specimens resemble those from the upper Tertiary of Victoria which Deflandre & Cookson (1955) identified with Spiniferites cingulatus (O. Wetzel ) and described as having no processes.