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Cribroperidinium aparsium
Cribroperidinium aparsium Stover and Helby, 1987
Holotype: Stover and Helby, 1987, fig.6A-D
Locus typicus: Exmouth Plateau, W Australia
Stratum typicum: Hauterivian-Aptian
Original description: Stover and Helby, 1987, p. 230-234
Cysts proximate, subspherical, with a prominent, asymmetrical, fibroid apical horn
17-26 Ám long with a truncated tip. Horn merges with the relatively thick (4 to slightly more than 5 Ám) autophragm, with 2-4 short, blunt processes on shaft and base. The outer, faintly and minutely pitted autophragm surface with low, continuous or interrupted parasutural ridges and short, nontabular tubercles (2-5 Ám long). Ridge crests smooth, or denticulate, and/or spinate. Nontabular tubercles may be separated, or adjacent ones may coalesce proximally to form discontinuous, straight or curved features. Parasutural ridges indicate a paratabulation of 4" 0a, 6"", Xc, 5-6""" , 1p, 1"""", and 2-5s. Archeopyle formed by the release of 3""; operculum normally free. At least some paraplates with clear to indistinct expressions of growth features, such as short accessory ridges within paraplate boundaries more or less parallel to the parasutural ridges. Paracingulum delimited by 2 transverse, parallel ridges whose spinate crests tend to be higher than others on the cyst, but not appreciably so. Paracingulum nearly always undivided, with its ends offset by approximately two times the width of the paracingulum. A longitudinal depression extending from the adcingular margin of 1" to the ventral margin of 1"""", encompassing the first postcingular and the posterior intercalary paraplates, together with the sulcal paraplates. Within the parasulcus, the anterior and posterior sulcal paraplates usually discernible; up to 3 additional sulcal paraplates and flagellar scar evident on some specimens. In overall length specimens 100-146 Ám and in width 92-120 Ám, 10 specimens measured.
Affinities:
Stover and Helby, 1987, p. 234: Cribroperidinium aparsium differs from C. diaphane (Cookson & Eisenack) Stover & Evitt 1978 in having a much thicker autophragm, shorter and more numerous nontabular projections, and less distinct accessory ridges (growth features). In fact, the accessory ridges, although present, are commonly difficult to trace. Consequently, assignment to Cribroperidinium is with some reservation.
Holotype: Stover and Helby, 1987, fig.6A-D
Locus typicus: Exmouth Plateau, W Australia
Stratum typicum: Hauterivian-Aptian
Original description: Stover and Helby, 1987, p. 230-234
Cysts proximate, subspherical, with a prominent, asymmetrical, fibroid apical horn
17-26 Ám long with a truncated tip. Horn merges with the relatively thick (4 to slightly more than 5 Ám) autophragm, with 2-4 short, blunt processes on shaft and base. The outer, faintly and minutely pitted autophragm surface with low, continuous or interrupted parasutural ridges and short, nontabular tubercles (2-5 Ám long). Ridge crests smooth, or denticulate, and/or spinate. Nontabular tubercles may be separated, or adjacent ones may coalesce proximally to form discontinuous, straight or curved features. Parasutural ridges indicate a paratabulation of 4" 0a, 6"", Xc, 5-6""" , 1p, 1"""", and 2-5s. Archeopyle formed by the release of 3""; operculum normally free. At least some paraplates with clear to indistinct expressions of growth features, such as short accessory ridges within paraplate boundaries more or less parallel to the parasutural ridges. Paracingulum delimited by 2 transverse, parallel ridges whose spinate crests tend to be higher than others on the cyst, but not appreciably so. Paracingulum nearly always undivided, with its ends offset by approximately two times the width of the paracingulum. A longitudinal depression extending from the adcingular margin of 1" to the ventral margin of 1"""", encompassing the first postcingular and the posterior intercalary paraplates, together with the sulcal paraplates. Within the parasulcus, the anterior and posterior sulcal paraplates usually discernible; up to 3 additional sulcal paraplates and flagellar scar evident on some specimens. In overall length specimens 100-146 Ám and in width 92-120 Ám, 10 specimens measured.
Affinities:
Stover and Helby, 1987, p. 234: Cribroperidinium aparsium differs from C. diaphane (Cookson & Eisenack) Stover & Evitt 1978 in having a much thicker autophragm, shorter and more numerous nontabular projections, and less distinct accessory ridges (growth features). In fact, the accessory ridges, although present, are commonly difficult to trace. Consequently, assignment to Cribroperidinium is with some reservation.