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Rimosicysta ovata
Rimosicysta? ovata Marshall 1989
Holotype. Marshall 1989: Plate 6, figs. 14-16.
Locus typicus: Gippsland Basin, Southeastern Australia
Stratum typicum: Late Cretaceous
Description. Marshall 1989, p. 48, 50
Cysts compressed dorsoventrally; with a distinct middorsal bulge; dorsoventral outline oval. Autophragm smooth, ca. 0.4 µm thick equatorially and thins markedly towards polar areas. Autophragm may be split apart parallel to cyst outline at one end of cyst. Possible parasulcus marked on midventral surface by a shallow longitudinal groove often bordered by two thickened folds.
Size. Autocyst length 65(78)90 µm, width 52(56)63 µm; 10 specimens measured.
Comparison. Marshall 1989, p. 48, 50
This taxon resembles other species of the genus in having a middorsal bulge. Possible parasulcus, and thinning of the autophragm and associated splitting around the periphery of the cyst. It differs in having a simple oval outline. Rimosicysta?ovata sp. nov. resembles the Triassic acritarch Bartenia communis Helby 1987 in having an oval outline and a markedly thinner cyst wall in the polar areas. Bartenia communis differs from this species in being smaller, flattened at the poles, and cavate.
Occurrence. Sunfish-l. 2482.7-2483.7 m.
Holotype. Marshall 1989: Plate 6, figs. 14-16.
Locus typicus: Gippsland Basin, Southeastern Australia
Stratum typicum: Late Cretaceous
Description. Marshall 1989, p. 48, 50
Cysts compressed dorsoventrally; with a distinct middorsal bulge; dorsoventral outline oval. Autophragm smooth, ca. 0.4 µm thick equatorially and thins markedly towards polar areas. Autophragm may be split apart parallel to cyst outline at one end of cyst. Possible parasulcus marked on midventral surface by a shallow longitudinal groove often bordered by two thickened folds.
Size. Autocyst length 65(78)90 µm, width 52(56)63 µm; 10 specimens measured.
Comparison. Marshall 1989, p. 48, 50
This taxon resembles other species of the genus in having a middorsal bulge. Possible parasulcus, and thinning of the autophragm and associated splitting around the periphery of the cyst. It differs in having a simple oval outline. Rimosicysta?ovata sp. nov. resembles the Triassic acritarch Bartenia communis Helby 1987 in having an oval outline and a markedly thinner cyst wall in the polar areas. Bartenia communis differs from this species in being smaller, flattened at the poles, and cavate.
Occurrence. Sunfish-l. 2482.7-2483.7 m.