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Operculodinium eisenackii
Operculodinium eisenackii Heilmann-Clausen and Van Simaeys, 2005, p.176–177, pl.8, figs.3–6.
Taxonomic junior synonym (at specific rank): Hystrichosphaeridium divergens forma areolatum, according to Heilmann-Clausen and Van Simaeys (2005, p.176).
Holotype: Heilmann-Clausen and Van Simaeys, 2005, pl.8, fig.5.
Age: middle Eocene.
Original description (heilmann-Clausen & van Simaeys, 2005):
Operculodinium eisenackii sp. nov. Plate 8, figs. 3–6
Hystrichosphaeridium divergensforma areolate Eisenack, 1954, p. 67, pl. 9, fig. 16.
Operculodinium tiara (Klumpp 1953) Stover & Evitt 1978; Brinkhuis and Biffi, 1993, pl. 8, fig. 8.
Operculodinium sp. aff. Cordosphaeridium funiculatum Morgenroth 1966; De Coninck, 2001, pl. 11, figs. 1, 2.
Description. Proximate to proximochorate dinoflagellate cysts with a subspherical to ellipsoidal outline. No paratabulation is indicated, except for the archeopyle. The autophragm is ornamented, with a distinct coarse reticulum consisting of a dense meshwork of solid low ridges. Numerous slender fibrous processes arise at the junctions of the ridges. The processes usually have short bifurcate or pointed endings. A few processes may be proximally connected by trabeculae. The process bases are broad. The length of the processes and the degree of reticulation differ between specimens. A tendency to shorter processes on less coarse reticulate cysts has been noted. The archeopyle is precingular (type P, 3'' only), the operculum is usually lost.
Derivation of name. For Alfred Eisenack, who first illustrated this species.
Designation of holotype. Plate 8, fig. 5, Slide 2664 H4, England Finder coordinates N52/1. MGUH 27780. Kysing- 4 borehole, sample 2664, Middle Eocene. Specimen dimensions: Total length 111 µm; total breadth 108 µm; central body length 69 µm; central body breadth 69 µm; maximum length of processes 23 µm.
Designation of Paratype. Paratype 1: Plate 8, fig. 3, Slide 2649 H1, England Finder coordinates S45. MGUH 27781. Kysing-4 borehole, sample 2649, Middle Eocene. Paratype 2: Plate 8, fig. 4, Slide 2661 H1, England Finder coordinates K55/1. MGUH 27782. Kysing-4 borehole, sample 2661, Middle Eocene.
Dimensions of measured specimens. Total length 90 (105) 117 µm. Total breadth 81 (96) 111 µm. Central body length 69 (74) 84 µm. Central body breadth 66 (69) 72 µm. Maximum length of processes 12–31 µm. Thickness of autophragm 2 (3) 4 µm. (11 specimens measured)
Comparison. Operculodinium eisenackii sp. nov. is identical to ‘forma areolata’ of Operculodinium divergens (Eisenack 1954) Stover & Evitt 1978 figured in Eisenack (1954, pl. 9, fig. 16). It differs from the Operculodinium divergens Group by the coarsely reticulate autophragm. It differs from Cordosphaeridium funiculatum Morgenroth 1966 by the more numerous, simple and slender fibrous processes.
Taxonomic junior synonym (at specific rank): Hystrichosphaeridium divergens forma areolatum, according to Heilmann-Clausen and Van Simaeys (2005, p.176).
Holotype: Heilmann-Clausen and Van Simaeys, 2005, pl.8, fig.5.
Age: middle Eocene.
Original description (heilmann-Clausen & van Simaeys, 2005):
Operculodinium eisenackii sp. nov. Plate 8, figs. 3–6
Hystrichosphaeridium divergensforma areolate Eisenack, 1954, p. 67, pl. 9, fig. 16.
Operculodinium tiara (Klumpp 1953) Stover & Evitt 1978; Brinkhuis and Biffi, 1993, pl. 8, fig. 8.
Operculodinium sp. aff. Cordosphaeridium funiculatum Morgenroth 1966; De Coninck, 2001, pl. 11, figs. 1, 2.
Description. Proximate to proximochorate dinoflagellate cysts with a subspherical to ellipsoidal outline. No paratabulation is indicated, except for the archeopyle. The autophragm is ornamented, with a distinct coarse reticulum consisting of a dense meshwork of solid low ridges. Numerous slender fibrous processes arise at the junctions of the ridges. The processes usually have short bifurcate or pointed endings. A few processes may be proximally connected by trabeculae. The process bases are broad. The length of the processes and the degree of reticulation differ between specimens. A tendency to shorter processes on less coarse reticulate cysts has been noted. The archeopyle is precingular (type P, 3'' only), the operculum is usually lost.
Derivation of name. For Alfred Eisenack, who first illustrated this species.
Designation of holotype. Plate 8, fig. 5, Slide 2664 H4, England Finder coordinates N52/1. MGUH 27780. Kysing- 4 borehole, sample 2664, Middle Eocene. Specimen dimensions: Total length 111 µm; total breadth 108 µm; central body length 69 µm; central body breadth 69 µm; maximum length of processes 23 µm.
Designation of Paratype. Paratype 1: Plate 8, fig. 3, Slide 2649 H1, England Finder coordinates S45. MGUH 27781. Kysing-4 borehole, sample 2649, Middle Eocene. Paratype 2: Plate 8, fig. 4, Slide 2661 H1, England Finder coordinates K55/1. MGUH 27782. Kysing-4 borehole, sample 2661, Middle Eocene.
Dimensions of measured specimens. Total length 90 (105) 117 µm. Total breadth 81 (96) 111 µm. Central body length 69 (74) 84 µm. Central body breadth 66 (69) 72 µm. Maximum length of processes 12–31 µm. Thickness of autophragm 2 (3) 4 µm. (11 specimens measured)
Comparison. Operculodinium eisenackii sp. nov. is identical to ‘forma areolata’ of Operculodinium divergens (Eisenack 1954) Stover & Evitt 1978 figured in Eisenack (1954, pl. 9, fig. 16). It differs from the Operculodinium divergens Group by the coarsely reticulate autophragm. It differs from Cordosphaeridium funiculatum Morgenroth 1966 by the more numerous, simple and slender fibrous processes.