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Semicavidinium mitra
Semicavidinium mitra (Dürr, 1987) Dodkova 1994
Originally Meiourogonyaulax, subsequently Lithodinia, thirdly (and now) Semicavidinium.
Holotype: Dürr, 1987, fig.4, no.3; Dürr, 1988, pl.1, fig.5.
Age: middle Kimmeridgian.
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Original description: [Dürr, 1987] (translated from German):
Meiourogonyaulax mitra n. sp.
Fig. 3; Fig. 4, Fig. 3-6; Fig. 6, Fig. 1-3, 5
Holotype: Specimen GPIT 1663/3, Fig. 4, Fig. 3.
Paratypoids: Specimens GPIT 1663/4-6, 1663/13 Nos. 26 and 30; Fig. 4, Fig. 4-6; Fig. 6, Fig. 1, 2.
Stratum typicalum: Border area of the White Jurassic S,/8, (mutabilis zone), sample W-3, at borehole depth 256.3. Gray limestone marl.
Locus typicalus: Borehole KB 3 (water) of the BN-Stollen planning association between Lake Constance and the Neckar. TK 25:8020 - Meßkirch; Coordinates: r^(35)505360/h^(53)14299.
Derivatio nominis: mitra (Latin) bishop's mitre; refers to the shape of the inverted cyst.
Diagnosis: Cyst subspherical to ovoid. The paracingulum and parasulcus are clearly depressed. The paratabulation is unclear, but the following paratabulation pattern is evident: 6", 6'", 1"", 4' (?) (Fig. 3). The cyst is cavate.
Description:
The peri- and endophragm are present and connected by trabecular structures, which accounts for the foamy appearance of Meiourogonyaulax mitra under the light microscope.
The cavity is significantly larger in the hypocyst than in the epicyst. The apical calotte is usually absent. To date, only one specimen (holotype) with an operculum has been found.
Meiourogonyaulax mitra differs from Meiourogonyaulax deflandrei (SARJEANT, 1968) and Meiourogonyaulax psoros (DAVEY & VERDIER, 1974) by the presence of a cavity.
Meiourogonyaulax stoveri (MILLIOUD, 1969) has a similar vacuolar wall structure, but differs from Meiourogonyaulax mitra by its more pronounced parasutures.
Dimensions:
Holotype: Length with operculum: 87 μm
Length without operculum: 69 μm
Width: 69 μm
Range of variation (30 measured specimens):
Length without operculum: 60-75 μm,
Width: 60-75 μm.
Occurrence: Only in the White Jurassic border region, delta 1/delta 2, (mutabilis zone) of southern Germany.
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Remarks. Dodkova 1994, p. 28
Dürr (1988, p. 84) mentions the cavation of the species. This is in conflict with the generic diagnosis of "Meiourogonyalllax . With all morphological features this species reveals differences which are considered to be significant at the generic level and did not coincides with any other generic dinocyst diagnosis. That is why it was necessary to errect a new genus Semicavidinium, and being cavate Meiourogonyaulax mitra does not belong in Meiourogonyaulax and requiring generic re-attribution is accepted as type species of the same. The new combination Semicavidinium mitra (Durr, 1987) is proposed. The intraspecific variability of the species is expressed as varying in height sutural and antapical cavities. The Bulgarian specimens coincide completely with description and photos of the German specimens.
Occurrence. Borehole R-1 Junak (depth 1605 m, Tica Fm., Middle Tithonian, Chitinoidella Zone).
Originally Meiourogonyaulax, subsequently Lithodinia, thirdly (and now) Semicavidinium.
Holotype: Dürr, 1987, fig.4, no.3; Dürr, 1988, pl.1, fig.5.
Age: middle Kimmeridgian.
------------------------------------------------------------------------------------------------------------
Original description: [Dürr, 1987] (translated from German):
Meiourogonyaulax mitra n. sp.
Fig. 3; Fig. 4, Fig. 3-6; Fig. 6, Fig. 1-3, 5
Holotype: Specimen GPIT 1663/3, Fig. 4, Fig. 3.
Paratypoids: Specimens GPIT 1663/4-6, 1663/13 Nos. 26 and 30; Fig. 4, Fig. 4-6; Fig. 6, Fig. 1, 2.
Stratum typicalum: Border area of the White Jurassic S,/8, (mutabilis zone), sample W-3, at borehole depth 256.3. Gray limestone marl.
Locus typicalus: Borehole KB 3 (water) of the BN-Stollen planning association between Lake Constance and the Neckar. TK 25:8020 - Meßkirch; Coordinates: r^(35)505360/h^(53)14299.
Derivatio nominis: mitra (Latin) bishop's mitre; refers to the shape of the inverted cyst.
Diagnosis: Cyst subspherical to ovoid. The paracingulum and parasulcus are clearly depressed. The paratabulation is unclear, but the following paratabulation pattern is evident: 6", 6'", 1"", 4' (?) (Fig. 3). The cyst is cavate.
Description:
The peri- and endophragm are present and connected by trabecular structures, which accounts for the foamy appearance of Meiourogonyaulax mitra under the light microscope.
The cavity is significantly larger in the hypocyst than in the epicyst. The apical calotte is usually absent. To date, only one specimen (holotype) with an operculum has been found.
Meiourogonyaulax mitra differs from Meiourogonyaulax deflandrei (SARJEANT, 1968) and Meiourogonyaulax psoros (DAVEY & VERDIER, 1974) by the presence of a cavity.
Meiourogonyaulax stoveri (MILLIOUD, 1969) has a similar vacuolar wall structure, but differs from Meiourogonyaulax mitra by its more pronounced parasutures.
Dimensions:
Holotype: Length with operculum: 87 μm
Length without operculum: 69 μm
Width: 69 μm
Range of variation (30 measured specimens):
Length without operculum: 60-75 μm,
Width: 60-75 μm.
Occurrence: Only in the White Jurassic border region, delta 1/delta 2, (mutabilis zone) of southern Germany.
------------------------------------------------------------------------------------------------------------
Remarks. Dodkova 1994, p. 28
Dürr (1988, p. 84) mentions the cavation of the species. This is in conflict with the generic diagnosis of "Meiourogonyalllax . With all morphological features this species reveals differences which are considered to be significant at the generic level and did not coincides with any other generic dinocyst diagnosis. That is why it was necessary to errect a new genus Semicavidinium, and being cavate Meiourogonyaulax mitra does not belong in Meiourogonyaulax and requiring generic re-attribution is accepted as type species of the same. The new combination Semicavidinium mitra (Durr, 1987) is proposed. The intraspecific variability of the species is expressed as varying in height sutural and antapical cavities. The Bulgarian specimens coincide completely with description and photos of the German specimens.
Occurrence. Borehole R-1 Junak (depth 1605 m, Tica Fm., Middle Tithonian, Chitinoidella Zone).