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Operculodinium divergens
From Fensome et al., 2019:
Operculodinium divergens (Eisenack, 1954b, p.67, pl.9, figs.13–16) Stover and Evitt, 1978, p.178. Holotype: Eisenack, 1954b, pl.9, fig.14. Originally Hystrichosphaeridium, subsequently Baltisphaeridium (combination not validly published; Appendix A), thirdly Cordosphaeridium, fourthly (and now) Operculodinium. Age: Early Oligocene.
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Original description (Eisenack, 1954b) Not yet translated from German.
Diagnosis: Central shell spherical to ellipsoidal, more or less smooth, granulated or areolated, with numerous processes, usually attached with a somewhat broadened base and divided into two, three, or more diverging ends, but without extending as much to the sides as in H. inodes. Eclosion holes are frequent, circular, and approximately 55% of the diameter of the central shell.
Description: The ellipsoid of the central shell can reach an axial ratio of up to 1:1.2. The shell is constructed similarly to that of H. inodes subsp. gracilis, i.e., it is often bilayered. Just as in this case, beautifully areolate specimens are found. The structure of the fibrous appendages is less distinct, but the formation of their ends bears a strong resemblance to that of H. inodes, except that they extend much less to the sides and remain more closely together. The hatching holes are relatively large. If the central shell is oval, the plane of the openings is usually parallel to the equator, perpendicular to the long axis; however, this can occasionally be cut somewhat obliquely. Well over 100 specimens have been preserved, of which 12 have beautifully areolate shells; these pieces are described as forma areolata.
Relationships: Judging by the shape and structure of the appendages, there is a relationship with H. inodes, however, the appendages are more numerous, relatively shorter, and the central shell is generally smaller than in the present subspecies of H. inodes. The appendages vary understandably. If they are only divided at the very end and the forking is very small, the species can be very reminiscent of H. hirsutum ehrenb., whose appendages, however, mostly end in undivided tips. There also seems to be a relationship with this species. Also included in this group appear to be H. cf. spinosum (White) Lejeune-Carpentier 1941, H. pseudhystrichodinium Defl., H. striolatum Defl., H. vestitum Defl., H. palmatum Defl. and others. The differentiation of such species from one another becomes more difficult the more individuals are found. Dimensions: Type specimen: diameter of the central shell: 71 µ; total diameter: 124 µ; the spherical diameter varies between 52 and 83 µ, the total diameter between 90 and 133 µ, the averages (50 specimens) are 67 µ and 111 µ, respectively.
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Operculodinium divergens (Eisenack, 1954b) Stover and Evitt, 1978. Diagnosis from Eisenack (1954b, p.67): Central body spherical to oval, more or less smooth, granulated or areolated, with numerous processes, which are tapering, and distally divided into two, three or more terminal portions which diverge from one another, without however bending back. Size: diameter of central body 52-83 µm, overall diameter 90-133 µm.
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Operculodinium divergens (Eisenack, 1954b, p.67, pl.9, figs.13–16) Stover and Evitt, 1978, p.178. Holotype: Eisenack, 1954b, pl.9, fig.14. Originally Hystrichosphaeridium, subsequently Baltisphaeridium (combination not validly published; Appendix A), thirdly Cordosphaeridium, fourthly (and now) Operculodinium. Age: Early Oligocene.
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Original description (Eisenack, 1954b) Not yet translated from German.
Diagnosis: Central shell spherical to ellipsoidal, more or less smooth, granulated or areolated, with numerous processes, usually attached with a somewhat broadened base and divided into two, three, or more diverging ends, but without extending as much to the sides as in H. inodes. Eclosion holes are frequent, circular, and approximately 55% of the diameter of the central shell.
Description: The ellipsoid of the central shell can reach an axial ratio of up to 1:1.2. The shell is constructed similarly to that of H. inodes subsp. gracilis, i.e., it is often bilayered. Just as in this case, beautifully areolate specimens are found. The structure of the fibrous appendages is less distinct, but the formation of their ends bears a strong resemblance to that of H. inodes, except that they extend much less to the sides and remain more closely together. The hatching holes are relatively large. If the central shell is oval, the plane of the openings is usually parallel to the equator, perpendicular to the long axis; however, this can occasionally be cut somewhat obliquely. Well over 100 specimens have been preserved, of which 12 have beautifully areolate shells; these pieces are described as forma areolata.
Relationships: Judging by the shape and structure of the appendages, there is a relationship with H. inodes, however, the appendages are more numerous, relatively shorter, and the central shell is generally smaller than in the present subspecies of H. inodes. The appendages vary understandably. If they are only divided at the very end and the forking is very small, the species can be very reminiscent of H. hirsutum ehrenb., whose appendages, however, mostly end in undivided tips. There also seems to be a relationship with this species. Also included in this group appear to be H. cf. spinosum (White) Lejeune-Carpentier 1941, H. pseudhystrichodinium Defl., H. striolatum Defl., H. vestitum Defl., H. palmatum Defl. and others. The differentiation of such species from one another becomes more difficult the more individuals are found. Dimensions: Type specimen: diameter of the central shell: 71 µ; total diameter: 124 µ; the spherical diameter varies between 52 and 83 µ, the total diameter between 90 and 133 µ, the averages (50 specimens) are 67 µ and 111 µ, respectively.
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Operculodinium divergens (Eisenack, 1954b) Stover and Evitt, 1978. Diagnosis from Eisenack (1954b, p.67): Central body spherical to oval, more or less smooth, granulated or areolated, with numerous processes, which are tapering, and distally divided into two, three or more terminal portions which diverge from one another, without however bending back. Size: diameter of central body 52-83 µm, overall diameter 90-133 µm.
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