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Invertocysta flandriensis
Invertocysta flandriensis Louwye, 1997, p.150, pl.1, figs.10-13.
Taxonomic senior synonym: Turnosphaera hypoflata, according to Slimani and Louwye (2012, p.110,114).
Holotype: Louwye, 1997, pl.1, figs.10-13.
Age: Turonian-Campanian.
Louwye, 1997; Invertocysta flandriensis n.sp. Pl. 1: 10-13
Derivatio nominis : The type locality, Knokke, is situated in Flanders (Vlaanderen)
Locus typicus and stratum typicum: Knokke, West-Flanders, Belgium, well no. 11E138, -347.6 m, Campanian.
Dimensions: holotype – length of pericyst, 62 µm; breasth of pericyst 62 µm; diameter of endocyst, 37 µm. Variations – length of pericyst, 56-72 µm; breadth of pericyst, 55-68 µm; diameter of endocyst, 34-41 µm. Number of specimens measured: 10.
Diagnosis: The outline of the cavate cyst is hexagonal with rounded angles to subcircular. Both endo- and periphragm are scabrate, the endophragm being slightly thicker than the periphragm. The outline of the endocyst is circular with a small apical boss, giving it a tear-like appearance. A similar small apical boss sometimes developed on the pericyst. The size of the endocyst is considerably smaller than the pericyst. Both walls are only on contact in the ventral region, the endocyst not being centered within the pericyst. The outward extemded periphragm forms a well-developed dorsal pericoel. Low, smooth parasutural ridges on the pericyst delineate a partial, probably gonyaulacean, paratabulation: four apical paraplates, precingulars 3 to 6 are the most clearly reflected paraplates. It is not clear whether the paracingulum is divided into paraplates. The paracingulum on the dorsal side is antapically displaced. The endoarcheopyle is of type P and formed by the release of paraplate 4. A large subquadratic opening occupies most of the dorsal side and corresponds to paraplate 4. The form and dimensions of the endo- and periarcheopyle are fairly constant.
Comparison: the paratabulation of Invertocysta tabulate Edwards, 1984 (Middle-late Miocene) is completely expressed on the pericyst. Furthermore, the endocyst of the latter species is centered within the pericyst. I. lacrimosa Edwards, 1984 (Middle-Late Miocene) differs in that the boss of the endocyst is connected to the inner lip of the bowl-shaped pericyst. It differs furthermore from our species by the wide variation in size, shape, degree of reflection of the paratabulation and the size of the dorsal opening.
Remarks: Due to th fragile nature of the periphragm, I. flandriensis is often found distorted in preparations.
Occurrence: Knokke: -405.1 m, -315.1 m (Campanian); DeHaan, -229.0m (Campanian); Keiem, -211.6 m, -204.0 m, -199.6 m (Turonian – Santonian); Nieuwkerke, -91.0 m (Santonian).
Taxonomic senior synonym: Turnosphaera hypoflata, according to Slimani and Louwye (2012, p.110,114).
Holotype: Louwye, 1997, pl.1, figs.10-13.
Age: Turonian-Campanian.
Louwye, 1997; Invertocysta flandriensis n.sp. Pl. 1: 10-13
Derivatio nominis : The type locality, Knokke, is situated in Flanders (Vlaanderen)
Locus typicus and stratum typicum: Knokke, West-Flanders, Belgium, well no. 11E138, -347.6 m, Campanian.
Dimensions: holotype – length of pericyst, 62 µm; breasth of pericyst 62 µm; diameter of endocyst, 37 µm. Variations – length of pericyst, 56-72 µm; breadth of pericyst, 55-68 µm; diameter of endocyst, 34-41 µm. Number of specimens measured: 10.
Diagnosis: The outline of the cavate cyst is hexagonal with rounded angles to subcircular. Both endo- and periphragm are scabrate, the endophragm being slightly thicker than the periphragm. The outline of the endocyst is circular with a small apical boss, giving it a tear-like appearance. A similar small apical boss sometimes developed on the pericyst. The size of the endocyst is considerably smaller than the pericyst. Both walls are only on contact in the ventral region, the endocyst not being centered within the pericyst. The outward extemded periphragm forms a well-developed dorsal pericoel. Low, smooth parasutural ridges on the pericyst delineate a partial, probably gonyaulacean, paratabulation: four apical paraplates, precingulars 3 to 6 are the most clearly reflected paraplates. It is not clear whether the paracingulum is divided into paraplates. The paracingulum on the dorsal side is antapically displaced. The endoarcheopyle is of type P and formed by the release of paraplate 4. A large subquadratic opening occupies most of the dorsal side and corresponds to paraplate 4. The form and dimensions of the endo- and periarcheopyle are fairly constant.
Comparison: the paratabulation of Invertocysta tabulate Edwards, 1984 (Middle-late Miocene) is completely expressed on the pericyst. Furthermore, the endocyst of the latter species is centered within the pericyst. I. lacrimosa Edwards, 1984 (Middle-Late Miocene) differs in that the boss of the endocyst is connected to the inner lip of the bowl-shaped pericyst. It differs furthermore from our species by the wide variation in size, shape, degree of reflection of the paratabulation and the size of the dorsal opening.
Remarks: Due to th fragile nature of the periphragm, I. flandriensis is often found distorted in preparations.
Occurrence: Knokke: -405.1 m, -315.1 m (Campanian); DeHaan, -229.0m (Campanian); Keiem, -211.6 m, -204.0 m, -199.6 m (Turonian – Santonian); Nieuwkerke, -91.0 m (Santonian).