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Operculodinium placitum
Operculodinum placitum Drugg and Loeblich, 1967
Tax. sr. synonyrn of Polysphaeridium cephalum Kar, 1979, according to Jain and Garg, 1991.
Stover and Evitt, 1978, considered this to be a problematical species of Operculodinium.
Holotype: Drugg and Loeblich, 1967, pl.1, figs.11a-b
Paratype: Drugg and Loeblich, 1967
Locus typicus: Hinds County, Mississippi, U.S.A.
Stratum typicum: Oligocene
Original diagnosis: Drugg and Loeblich, 1967, p.186
Tract small, elliptical in outline. The precingular archeopyle is more or less elliptical in outline at the top with a squared-off lower edge. It is located on the upper face of the tract and extends from near the apex to the equator. The wall is about 1 to 1.5 Ám thick, endophragm thinner than periphragm. The latter is finely granulate ar.d ornamented with short, more or less blunt, spines of about 1Ám in length. These spines are spaced approximately 1 to 2 Ám apart and do not reflect any apparent tabulation.
Dimenisons: Holotype, 36 Ám high, 27 Ám wide; paratype 37 Ám high, 32 Ám wide; range 32 to 39 Ám high, 24 to 32 Ám wide; average dimensions about 36 Ám high, 28 Ám wide.
Affinities:
Drugg and Loeblich, 1967, p.186: This species has been placed in the genus Operculodinium because of its precingular archeopyle and spinose ornamentation. It does not, however, exhibit any indication of spine arrangements suggestive of plate patterns, and there is no indication of a cingulum or sulcus. As regards described species it most closely resembles Pyxidiella pandora Cookson and Eisenack, 1958, and P. scrobiculata (Deflandre and Cookson) Cookson and Eisenack, 1958. It differs from the former in its smaller size and in bearing coarser and more scattered ornamentation. It differs from P. scrobiculata in the smaller size, and thinner nonpunctate wall. From both species it differs in possessing a precingular archeopyle instead of an intercalary archeopyle.
Heilmann-Clausen in Heilmann-Clausen and Costa, 1989, p. 469-470, pl.16,figs.4,5: Operculodinium aff. placitum
De Coninck, ?1976: Operculodinium aff. placitum
De Coninck, ?1986: Operculodinium aff. placitum
The two specimens seen at 370.0 m are rather similar to those figured by De Coninck, 1976, 1986, although with less distinct granulation of the cyst surface and less well defined spines. The specimens in the rich material at 348.0 m and above are usually distinctly grarlular with more numerous and more robust processes.
The processes are much longer than in D. placitum.
Tax. sr. synonyrn of Polysphaeridium cephalum Kar, 1979, according to Jain and Garg, 1991.
Stover and Evitt, 1978, considered this to be a problematical species of Operculodinium.
Holotype: Drugg and Loeblich, 1967, pl.1, figs.11a-b
Paratype: Drugg and Loeblich, 1967
Locus typicus: Hinds County, Mississippi, U.S.A.
Stratum typicum: Oligocene
Original diagnosis: Drugg and Loeblich, 1967, p.186
Tract small, elliptical in outline. The precingular archeopyle is more or less elliptical in outline at the top with a squared-off lower edge. It is located on the upper face of the tract and extends from near the apex to the equator. The wall is about 1 to 1.5 Ám thick, endophragm thinner than periphragm. The latter is finely granulate ar.d ornamented with short, more or less blunt, spines of about 1Ám in length. These spines are spaced approximately 1 to 2 Ám apart and do not reflect any apparent tabulation.
Dimenisons: Holotype, 36 Ám high, 27 Ám wide; paratype 37 Ám high, 32 Ám wide; range 32 to 39 Ám high, 24 to 32 Ám wide; average dimensions about 36 Ám high, 28 Ám wide.
Affinities:
Drugg and Loeblich, 1967, p.186: This species has been placed in the genus Operculodinium because of its precingular archeopyle and spinose ornamentation. It does not, however, exhibit any indication of spine arrangements suggestive of plate patterns, and there is no indication of a cingulum or sulcus. As regards described species it most closely resembles Pyxidiella pandora Cookson and Eisenack, 1958, and P. scrobiculata (Deflandre and Cookson) Cookson and Eisenack, 1958. It differs from the former in its smaller size and in bearing coarser and more scattered ornamentation. It differs from P. scrobiculata in the smaller size, and thinner nonpunctate wall. From both species it differs in possessing a precingular archeopyle instead of an intercalary archeopyle.
Heilmann-Clausen in Heilmann-Clausen and Costa, 1989, p. 469-470, pl.16,figs.4,5: Operculodinium aff. placitum
De Coninck, ?1976: Operculodinium aff. placitum
De Coninck, ?1986: Operculodinium aff. placitum
The two specimens seen at 370.0 m are rather similar to those figured by De Coninck, 1976, 1986, although with less distinct granulation of the cyst surface and less well defined spines. The specimens in the rich material at 348.0 m and above are usually distinctly grarlular with more numerous and more robust processes.
The processes are much longer than in D. placitum.