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Eisenackia knokkensis
Eisenackia knokkensis Louwye, 1997, p.149-150, pl.1, figs.7-9.
Questionable assignment: Louwye (1997, p.149).
Holotype: Louwye, 1997, pl.1, figs.8-9.
Age: Campanian.
(Louwye, 1997):
Derivatio nominis: “Knokke”: the location of the well.
Holotype: Knokke well 11E138, -420.7 m, P.1, coord. E.F. G-23.4 (Pl. 1, figs. 8-9), repository; collection of the laboratory of Paleontology, university of Ghent.
Locus typicus and stratum typicum: Knokke, West Flanders, Belgium, well no. 11E138
Dimensions: Holotype: width, 58 µm, length (without operculum), 50 µm. variation: width 54-63 µm; length (without operculum), 45-58 µm. Number of measured specimens: 11.
Diagnosis: the proximate, moderately compressed cyst has a subsherical outline in dorsoventral view. A small apical protrusion is sometimes developed while the antapex in rounded. The thin Autophragm is ornamented with a low but rather dense and coarse granulation of the intratabular areas. The paratabulation is clearly reflected by the absence of this ornamentation in the parasutural areas. The hypocyst is somewhat larger than the epicyst. The hypocystal arrangement is sexiform gonyaulacoid with an almost symmetrical Y. The contact between Y and VI, and Y and X is reduced. Z has a blocked appearances, is almost square in outline and has a convex contact with Y. Im is larger lager than li, the latter is poorly delineated and seem sometimes to be bipartite, ai has an elongated shape, while fu is triangular with convex sides. The archeopyle is of type (ta). The free operculum consists of four apical paraplates and has been observed adherent in a few cases only. A deep parasulcal notch is developed.
Comparison: Eisenackia crassitabulata Deflandre & Cookson, 1955 (Paleocene - Early Eocene) differs by the ellipsoidal ambitus, the thick wall, the type of ornamentation and the hypocystal quinqueform arrangement. Stoveracysta ornate (Cookson & Eisenack, 1965) Clowes, 1985 (Late Eocene) differs by the presence of the two short antapical lobes, the penitabular ledges, the circular ambitus in apical view and the ventral organization and ornamentation.
Remarks: This species has the essential characteristicas (type of ornamentation, shape) of the genus Eisenackia but differs by its sexiform hypocystal arrangement; hence the doubtful assignment to this genus.
Questionable assignment: Louwye (1997, p.149).
Holotype: Louwye, 1997, pl.1, figs.8-9.
Age: Campanian.
(Louwye, 1997):
Derivatio nominis: “Knokke”: the location of the well.
Holotype: Knokke well 11E138, -420.7 m, P.1, coord. E.F. G-23.4 (Pl. 1, figs. 8-9), repository; collection of the laboratory of Paleontology, university of Ghent.
Locus typicus and stratum typicum: Knokke, West Flanders, Belgium, well no. 11E138
Dimensions: Holotype: width, 58 µm, length (without operculum), 50 µm. variation: width 54-63 µm; length (without operculum), 45-58 µm. Number of measured specimens: 11.
Diagnosis: the proximate, moderately compressed cyst has a subsherical outline in dorsoventral view. A small apical protrusion is sometimes developed while the antapex in rounded. The thin Autophragm is ornamented with a low but rather dense and coarse granulation of the intratabular areas. The paratabulation is clearly reflected by the absence of this ornamentation in the parasutural areas. The hypocyst is somewhat larger than the epicyst. The hypocystal arrangement is sexiform gonyaulacoid with an almost symmetrical Y. The contact between Y and VI, and Y and X is reduced. Z has a blocked appearances, is almost square in outline and has a convex contact with Y. Im is larger lager than li, the latter is poorly delineated and seem sometimes to be bipartite, ai has an elongated shape, while fu is triangular with convex sides. The archeopyle is of type (ta). The free operculum consists of four apical paraplates and has been observed adherent in a few cases only. A deep parasulcal notch is developed.
Comparison: Eisenackia crassitabulata Deflandre & Cookson, 1955 (Paleocene - Early Eocene) differs by the ellipsoidal ambitus, the thick wall, the type of ornamentation and the hypocystal quinqueform arrangement. Stoveracysta ornate (Cookson & Eisenack, 1965) Clowes, 1985 (Late Eocene) differs by the presence of the two short antapical lobes, the penitabular ledges, the circular ambitus in apical view and the ventral organization and ornamentation.
Remarks: This species has the essential characteristicas (type of ornamentation, shape) of the genus Eisenackia but differs by its sexiform hypocystal arrangement; hence the doubtful assignment to this genus.