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Horologinella pentagonalis
Horologinella pentagonalis Heilmann-Clausen and Van Simaeys, 2005, p.170, pl.5, figs.10–13.
Questionable assignment: Heilmann-Clausen and Van Simaeys (2005, p.170); the authors noted that "... none of the specimens ... exhibit diagnostic dinoflagellate cyst features ...."
Holotype: Heilmann-Clausen and Van Simaeys, 2005, pl.5, fig.10.
Age: late Eocene.
Original description (Heilmann-Clausen and Van Simaeys, 2005):
Horologinella? pentagonalis sp. nov. Plate 5, figs. 10–13
Description. A medium-sized palynomorph composed of a thin walled, smooth, subspherical to angular central body. The surface is subdivided into polygonal fields. Two of the fields, occurring on opposite surfaces of the central body, are regular pentagons. All fields are bordered by high, thin and flexible septa. The distal margins of the septa are smooth. A deep and narrow invagination is present in one side of the holotype, but has not been observed in the paratypes. No archeopyle or other kind of opening in the wall has been observed.
Derivation of name. From the Greek pentagon, with reference to the presence of the five-sided fields.
Designation of holotype. Plate 5, fig. 10, Slide 1930 G2, England Finder coordinates L34/4. MGUH 27777. Kysing- 3 borehole, sample 1930, Upper Eocene. Specimen dimensions: Total diameter 42 µm; central body diameter 30 µm; maximum height of septa 6 µm.
Designation of paratype. Paratype 1: Plate 5, figs. 12, 13, Slide 1930 G1, England Finder coordinates J55. MGUH 27778. Kysing-3 borehole, sample 1930, Upper Eocene. Paratype 2: Plate 5, fig. 11, Slide 1928 G1, England Finder coordinates S50/3. MGUH 27779. Kysing-3 borehole, sample 1928, Upper Eocene.
Dimensions of measured specimens. Total diameter 42 (54) 68 µm. Central body diameter 30 (41) 45 µm. Maximum height of septa 6 (9) 15 µm. (8 specimens measured)
Comparison. A palynomorph of uncertain affinity, Horologinella? sp. 1, described by De Coninck (1999) from approximately coeval strata is undoubtedly a related taxon. It differs by being quadrangular, rather than pentagonal, in outline and is much smaller. Horologinella? pentagonalis sp. nov. superficially resembles certain thinwalled species of the dinoflagellate cyst Impagidinium, in particular Impagidinium pallidum Bujak 1984 and Impagidinium strialatum (Wall 1967) Stover & Evitt 1978. However, none of the many specimens recovered exhibit diagnostic dinoflagellate cyst features, such as an archeopyle, paracingulum, parasulcus or other manifestations of paratabulation. The assignment to the dinoflagellate cyst genus Horologinella and the Division Dinoflagellata is therefore provisional.
Questionable assignment: Heilmann-Clausen and Van Simaeys (2005, p.170); the authors noted that "... none of the specimens ... exhibit diagnostic dinoflagellate cyst features ...."
Holotype: Heilmann-Clausen and Van Simaeys, 2005, pl.5, fig.10.
Age: late Eocene.
Original description (Heilmann-Clausen and Van Simaeys, 2005):
Horologinella? pentagonalis sp. nov. Plate 5, figs. 10–13
Description. A medium-sized palynomorph composed of a thin walled, smooth, subspherical to angular central body. The surface is subdivided into polygonal fields. Two of the fields, occurring on opposite surfaces of the central body, are regular pentagons. All fields are bordered by high, thin and flexible septa. The distal margins of the septa are smooth. A deep and narrow invagination is present in one side of the holotype, but has not been observed in the paratypes. No archeopyle or other kind of opening in the wall has been observed.
Derivation of name. From the Greek pentagon, with reference to the presence of the five-sided fields.
Designation of holotype. Plate 5, fig. 10, Slide 1930 G2, England Finder coordinates L34/4. MGUH 27777. Kysing- 3 borehole, sample 1930, Upper Eocene. Specimen dimensions: Total diameter 42 µm; central body diameter 30 µm; maximum height of septa 6 µm.
Designation of paratype. Paratype 1: Plate 5, figs. 12, 13, Slide 1930 G1, England Finder coordinates J55. MGUH 27778. Kysing-3 borehole, sample 1930, Upper Eocene. Paratype 2: Plate 5, fig. 11, Slide 1928 G1, England Finder coordinates S50/3. MGUH 27779. Kysing-3 borehole, sample 1928, Upper Eocene.
Dimensions of measured specimens. Total diameter 42 (54) 68 µm. Central body diameter 30 (41) 45 µm. Maximum height of septa 6 (9) 15 µm. (8 specimens measured)
Comparison. A palynomorph of uncertain affinity, Horologinella? sp. 1, described by De Coninck (1999) from approximately coeval strata is undoubtedly a related taxon. It differs by being quadrangular, rather than pentagonal, in outline and is much smaller. Horologinella? pentagonalis sp. nov. superficially resembles certain thinwalled species of the dinoflagellate cyst Impagidinium, in particular Impagidinium pallidum Bujak 1984 and Impagidinium strialatum (Wall 1967) Stover & Evitt 1978. However, none of the many specimens recovered exhibit diagnostic dinoflagellate cyst features, such as an archeopyle, paracingulum, parasulcus or other manifestations of paratabulation. The assignment to the dinoflagellate cyst genus Horologinella and the Division Dinoflagellata is therefore provisional.