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Dissiliodinium minimum
Dissiliodinium minimum Feist-Burkhardt and Monteil, 2001, p.71-72, fig.3, nos.1-2; fig.6b; fig.11, nos.1-9; fig.12, nos.1-4; fig.19, no.1; table 2 (part).
Holotype: Feist-Burkhardt and Monteil, 2001, fig.3, no.1; fig.11, nos.1-3.
Age: Late Bajocian-Early Bathonian.
Original description (Feist-Burkhardt and Monteil, 2001)
Derivation of name: The specific epithet, minimum, is derived from the Latin minimus (=very small) referring to the very small size of the cyst,
Description: Cyst proximate, subspherical with a small apical bulge. Autophragm thin, densely ornamented bylichen-like anastomosing elements, orgianised in fine meshes (SEM). Many specimens show groth patterns (Fig. 1, 2, 3) Archeopyle precingular, compound, variable, formed by the loss of up t 5 precingular paraplates (1’’-5’’), opercular pieces free, adherent partially detached or adherent in place. Paratabulation appearing in transmitted light microcopy (TLM) indicated by archeopyle and by a faint parasulcal depression only, but completely indicated by penitabular ornamentation in SEM. Apical cap remains generally attached to the hypocyst by an isthmus consisting of the pparaplates 6’’, as, and sometimes, 1’’. Paraplates of the apical cap not differentiated in TLM, but completely marked in SEM. Apical cap outline indicates the presence of four apical and two dorsal anterior intercalary paraplates. Paratabulation gonyaulacaean, formula: ?pr, 4’, 2a, 6’’, 6c, 1p, 1’’’’, as + xs. Precingular paraplate of subequal size and stalked, except for 3’’; paraplate 3’’ distinctly showing the 1a notch (Fig. 1, 2, 3). Torsion neutral. Paracingulum laevorotatory, clearly subdivided in SEM. Parasulcal area indicated by a faint depression and the reduction of ornamentation. L-type ventral organization.
Dimensions: Holotype: 36 µm in diameter at paracingulum (not compressed specimen in glycerine jelly slide); range in glycerine jelly slides 34-40 µm in diameter at paracingulum (not compressed specimens), in SEM: 27-32 µm.
Comparison: D. minimum n.sp. differs from all other described Dissiliodinium species by its small size and its particular ornamentation. D. fragile (Kunz 1990) comb. nov. has no dorsal anterior intercalary paraplates (see Tab. 2)
Stratigraphical and geographical occurrence: Feist-Burkhardt & Monteil (1998): Normandy, NW-France, Upper Bajocian, top Parkinsoni Zone, Bomfordi Subzone to Early Bathonian, Tenuiplicatus Zone
Holotype: Feist-Burkhardt and Monteil, 2001, fig.3, no.1; fig.11, nos.1-3.
Age: Late Bajocian-Early Bathonian.
Original description (Feist-Burkhardt and Monteil, 2001)
Derivation of name: The specific epithet, minimum, is derived from the Latin minimus (=very small) referring to the very small size of the cyst,
Description: Cyst proximate, subspherical with a small apical bulge. Autophragm thin, densely ornamented bylichen-like anastomosing elements, orgianised in fine meshes (SEM). Many specimens show groth patterns (Fig. 1, 2, 3) Archeopyle precingular, compound, variable, formed by the loss of up t 5 precingular paraplates (1’’-5’’), opercular pieces free, adherent partially detached or adherent in place. Paratabulation appearing in transmitted light microcopy (TLM) indicated by archeopyle and by a faint parasulcal depression only, but completely indicated by penitabular ornamentation in SEM. Apical cap remains generally attached to the hypocyst by an isthmus consisting of the pparaplates 6’’, as, and sometimes, 1’’. Paraplates of the apical cap not differentiated in TLM, but completely marked in SEM. Apical cap outline indicates the presence of four apical and two dorsal anterior intercalary paraplates. Paratabulation gonyaulacaean, formula: ?pr, 4’, 2a, 6’’, 6c, 1p, 1’’’’, as + xs. Precingular paraplate of subequal size and stalked, except for 3’’; paraplate 3’’ distinctly showing the 1a notch (Fig. 1, 2, 3). Torsion neutral. Paracingulum laevorotatory, clearly subdivided in SEM. Parasulcal area indicated by a faint depression and the reduction of ornamentation. L-type ventral organization.
Dimensions: Holotype: 36 µm in diameter at paracingulum (not compressed specimen in glycerine jelly slide); range in glycerine jelly slides 34-40 µm in diameter at paracingulum (not compressed specimens), in SEM: 27-32 µm.
Comparison: D. minimum n.sp. differs from all other described Dissiliodinium species by its small size and its particular ornamentation. D. fragile (Kunz 1990) comb. nov. has no dorsal anterior intercalary paraplates (see Tab. 2)
Stratigraphical and geographical occurrence: Feist-Burkhardt & Monteil (1998): Normandy, NW-France, Upper Bajocian, top Parkinsoni Zone, Bomfordi Subzone to Early Bathonian, Tenuiplicatus Zone