Back
Ellipsoidictyum imperfectum ssp. quadrum
From Fensome et al., 2019:
Ellipsoidictyum inperfectum ssp. quadrum Duxbury, 2019, p.190–191, pl.17, fig.1; pl.18, figs.1,6,10. Holotype: Duxbury, 2019, pl.18, figs.1,6,10. Age: middle? Aptian.
---------------------------------------------------------------------------------------------------
Original description Duxbury, 2019
Holotype: Plate 18, Figures 1, 6, 10
Paratype: Plate 17, Figure 1
Type Locality: Heslerton No. 2 at 11.50 m (core chip), “mid”
Aptian. Holotype: E.F. F47.3. Paratype: E.F. N25.4
Derivation of Name: From the Latin quadrus, square - in reference to the outline of this subspecies.
Diagnosis: A subspecies of Ellipsoidictyum imperfectum with significant elevation of the reticular height along linear features which appear to be sutural and to mark an indistinct gonyaulacoid tabulation. The linear features are highest in presumed gonal areas, particularly on the hypocyst, and their crests are smooth or may have some minor irregularity. In optical section, the cyst has an angular, often quadrate appearance. Archeopyle tetratabular apical.
Dimensions: Holotype (complete): 61 × 63 μm.
Paratype (operculum missing): 53 × 63 μm.
All measured specimens with operculum missing: 58 (54) 48 μm × 63 (55) 48 μm.
Specimens Measured: 10.
Remarks: This subspecies was restricted to the 11.50 m and 10.85 m samples from Heslerton No. 2, where it was common; its FAD may prove to be a valuable “mid” Aptian marker.
Ellipsoidictyum imperfectum subsp. quadrum n. subsp. is closely similar to E. imperfectum subsp. imperfectum, as described by Brideaux and McIntyre (1975, p. 25, 26), differing only in the presence of distinctive raised linear features. Dorso-ventral compression is typical, and some specimens display significant reduction in reticulation which, together with the high linear features, presumably delineates gonyaulacoid tabulation.
Aspecimen of a late Aptian age from Sarstedt figured by Below (1982a, Figure 8) as E. imperfectum has been assigned to this subspecies, although its tabulation appears to be unusually clearly-marked compared to the Heslerton No. 2 material.
Ellipsoidictyum inperfectum ssp. quadrum Duxbury, 2019, p.190–191, pl.17, fig.1; pl.18, figs.1,6,10. Holotype: Duxbury, 2019, pl.18, figs.1,6,10. Age: middle? Aptian.
---------------------------------------------------------------------------------------------------
Original description Duxbury, 2019
Holotype: Plate 18, Figures 1, 6, 10
Paratype: Plate 17, Figure 1
Type Locality: Heslerton No. 2 at 11.50 m (core chip), “mid”
Aptian. Holotype: E.F. F47.3. Paratype: E.F. N25.4
Derivation of Name: From the Latin quadrus, square - in reference to the outline of this subspecies.
Diagnosis: A subspecies of Ellipsoidictyum imperfectum with significant elevation of the reticular height along linear features which appear to be sutural and to mark an indistinct gonyaulacoid tabulation. The linear features are highest in presumed gonal areas, particularly on the hypocyst, and their crests are smooth or may have some minor irregularity. In optical section, the cyst has an angular, often quadrate appearance. Archeopyle tetratabular apical.
Dimensions: Holotype (complete): 61 × 63 μm.
Paratype (operculum missing): 53 × 63 μm.
All measured specimens with operculum missing: 58 (54) 48 μm × 63 (55) 48 μm.
Specimens Measured: 10.
Remarks: This subspecies was restricted to the 11.50 m and 10.85 m samples from Heslerton No. 2, where it was common; its FAD may prove to be a valuable “mid” Aptian marker.
Ellipsoidictyum imperfectum subsp. quadrum n. subsp. is closely similar to E. imperfectum subsp. imperfectum, as described by Brideaux and McIntyre (1975, p. 25, 26), differing only in the presence of distinctive raised linear features. Dorso-ventral compression is typical, and some specimens display significant reduction in reticulation which, together with the high linear features, presumably delineates gonyaulacoid tabulation.
Aspecimen of a late Aptian age from Sarstedt figured by Below (1982a, Figure 8) as E. imperfectum has been assigned to this subspecies, although its tabulation appears to be unusually clearly-marked compared to the Heslerton No. 2 material.