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Microdinium pauciscabrosum
From Fensome et al., 2019:
Microdinium pauciscabrosum Slimani, 1994, p.39–41, pl.4, figs.28–29; pl.6, figs.9–10,26–27. Holotype: Slimani, 1994, pl.6,
figs.9–10,26–27. Age: late Campanian–late Maastrichtian.
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Original description (Slimani 1994):
Microdinium pauciscabrosum sp. nov. (P1.4, Fig. 28, 29; PI. 6, Fig. 9, 10, 26, 27)
Name derivation: Latin: pauci, small number; scabrosus, scabrous; reference to the slightly scabrous cyst.
Holotvpc: Turnhout -874 m, preparation 6, EF coord. T34/4.
Paratvpe: Turnhout -815.89 m, preparation 2, EF coord. Z45/2.
Type locality: Turnhout -874 m.
Horizon type: Lower Maastrichtian
Diagnosis: Small ellipsoidal to ovoid cyst with an epicyst smaller than the hypocyst. It bears thin, rigid, suturocavate ridges that delimit smooth to slightly scabrous intratabular areas. The paratabulation is gonyaulacoid and corresponds to the formula: lpr,4',4a,7",7c,6"', lp, 1"", 3-5s. The archaeopyle is apical and intercalary, type (tAtl)a, with an operculum attached to its ventral edge.
Dimensions: Holotype: length: 25 µm, width: 20 µm. Variations: length: 22-28 µm, width: 20-22 µm.
Number of specimens measured: 15.
Material: 20 specimens.
Description: The cyst is smooth to slightly scabrous over the entire intratabular surface or its central region. The endophragm (1 µm thick) and the very thin periphragm are adjacent throughout the cyst except at the parasutures, where the periphragm forms cava-like ridges. The ridges are glabrous, low (1 to 2 µm), and distally acute. The 7" paraplate is very reduced. The paracingulum (3 to 4 µm wide) is very slightly laevorotatory or non-spiral; 7c is smaller than the other cingulate paraplates. The parasulcus consists of 4 small paraplates (as, fm, rs, is) and ps which is wide and omegaform; rs and is are sometimes indistinguishable. The hypocystal configuration is partiform. The operculum is composed of 9 small apical paraplates: 1 preapical, 4 apical and 4 anterior intercalary.
Comparison: This type of cyst has topological characteristics comparable to those of Fibradinium? squamosum (BELOW, 1987b) LENTIN and WILLIAMS (1989) found in the lower Oligocene of Germany; but it differs mainly in its smaller size and in its smooth endophragm instead of a spongy one, which is the most probable character on which Lentin and Williams based their provisional assignment to the genus Fibradinium. Since these two types of cysts are observed with different means, the comparison between their parasutural ridges is in our opinion questionable. In optical microscopy, the ridges in Microdimum pauciscabrosum sp. nov. are suturocavate and distally acute, the periphragm that forms them is continuous; while in Fibradinium? squamosum, the original material of which is only observed in SEM by Below, the paratabulation is indicated by furrows or by ridges that result from the overlapping of the periphragm on the margins of the paraplates, the periphragm in the latter case seems discontinuous. In any case, M. pauciscabrosum sp. nov. resembles a little more the specimens found in the lower Maastrichtian of Germany, and attributed to Ph. squamosum by MARHEINECKE (1992: p. 24, fig. 5-12); but the latter author mentioned in his remark that these specimens are comparable with the forms of the type material, without mentioning the spongy or non-spongy nature of the endophragm.
Stratigraphic distribution: Turnhout: -933 to -815.89 m, Upper Campanian - lower part of the Upper Maastrichtian.
Microdinium pauciscabrosum Slimani, 1994, p.39–41, pl.4, figs.28–29; pl.6, figs.9–10,26–27. Holotype: Slimani, 1994, pl.6,
figs.9–10,26–27. Age: late Campanian–late Maastrichtian.
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Original description (Slimani 1994):
Microdinium pauciscabrosum sp. nov. (P1.4, Fig. 28, 29; PI. 6, Fig. 9, 10, 26, 27)
Name derivation: Latin: pauci, small number; scabrosus, scabrous; reference to the slightly scabrous cyst.
Holotvpc: Turnhout -874 m, preparation 6, EF coord. T34/4.
Paratvpe: Turnhout -815.89 m, preparation 2, EF coord. Z45/2.
Type locality: Turnhout -874 m.
Horizon type: Lower Maastrichtian
Diagnosis: Small ellipsoidal to ovoid cyst with an epicyst smaller than the hypocyst. It bears thin, rigid, suturocavate ridges that delimit smooth to slightly scabrous intratabular areas. The paratabulation is gonyaulacoid and corresponds to the formula: lpr,4',4a,7",7c,6"', lp, 1"", 3-5s. The archaeopyle is apical and intercalary, type (tAtl)a, with an operculum attached to its ventral edge.
Dimensions: Holotype: length: 25 µm, width: 20 µm. Variations: length: 22-28 µm, width: 20-22 µm.
Number of specimens measured: 15.
Material: 20 specimens.
Description: The cyst is smooth to slightly scabrous over the entire intratabular surface or its central region. The endophragm (1 µm thick) and the very thin periphragm are adjacent throughout the cyst except at the parasutures, where the periphragm forms cava-like ridges. The ridges are glabrous, low (1 to 2 µm), and distally acute. The 7" paraplate is very reduced. The paracingulum (3 to 4 µm wide) is very slightly laevorotatory or non-spiral; 7c is smaller than the other cingulate paraplates. The parasulcus consists of 4 small paraplates (as, fm, rs, is) and ps which is wide and omegaform; rs and is are sometimes indistinguishable. The hypocystal configuration is partiform. The operculum is composed of 9 small apical paraplates: 1 preapical, 4 apical and 4 anterior intercalary.
Comparison: This type of cyst has topological characteristics comparable to those of Fibradinium? squamosum (BELOW, 1987b) LENTIN and WILLIAMS (1989) found in the lower Oligocene of Germany; but it differs mainly in its smaller size and in its smooth endophragm instead of a spongy one, which is the most probable character on which Lentin and Williams based their provisional assignment to the genus Fibradinium. Since these two types of cysts are observed with different means, the comparison between their parasutural ridges is in our opinion questionable. In optical microscopy, the ridges in Microdimum pauciscabrosum sp. nov. are suturocavate and distally acute, the periphragm that forms them is continuous; while in Fibradinium? squamosum, the original material of which is only observed in SEM by Below, the paratabulation is indicated by furrows or by ridges that result from the overlapping of the periphragm on the margins of the paraplates, the periphragm in the latter case seems discontinuous. In any case, M. pauciscabrosum sp. nov. resembles a little more the specimens found in the lower Maastrichtian of Germany, and attributed to Ph. squamosum by MARHEINECKE (1992: p. 24, fig. 5-12); but the latter author mentioned in his remark that these specimens are comparable with the forms of the type material, without mentioning the spongy or non-spongy nature of the endophragm.
Stratigraphic distribution: Turnhout: -933 to -815.89 m, Upper Campanian - lower part of the Upper Maastrichtian.