Back
Operculodinium eirikianum
Operculodinium? eirikianum Head et al., 1989; Emendation: Head, 1997, p.180.
Head et al., 1989, questionably included this species in Operculodinium.
Holotype: Head et al., 1989, pl.4, figs.11,15-16
Locus typicus: Eirik Ridge, Labrador Sea, S of Greenland
Stratum typicum: Late Miocene-Early Pliocene
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Operculodinium eirikianum Head et al., 1989b, emend. Head, 1997. According to Head (1997), Operculodinium eirikianum is skolochorate with spherical central body. Wall consists of pedium (less than 0.2 µm thick) and thicker luxuria forming an irregular microreticulum of sinuous undulating muri about 0.2-0.3 µm wide that enclose lumina, mostly of about 0.5 µm or less in diameter. Processes solid, nonfibrous, with circular cross section for most of their length, may have scattered fine granules over surface, often become sinuous distally, and taper gradually to an acuminate tip. Process distribution apparently non-tabular. Each process arises either directly from surface or from a ridge that is low, short (about 6 µm or less), narrow, and straight or slightly arcuate. Archeopyle precingular type P(3"), deltacamerate with smooth margins, angles well defined. No accessory sutures. Operculum free. Size: diameter central body 33-42 µm, process length 5-10 µm, wall thickness up to 1.5 µm, but usually 1 µm or less.
--------------------------------------------------
Original description: Head et al. 1989, p. 459
Diagnosis: Cysts skolochorate, having a spherical body and nontabular processes. Cyst wall apparently single layered; solid and nonfibrous and has a prominently microreticulate surface. Processes are solid, circular in cross section, nonfibrous and taper gradually to an acuminate tip. They are often sinuous towards the tips and may have scattered fine granules over their surface. Archeopyle precingular Type P (presumably by loss of paraplate 3''). Operculum free.
Dimensions: Range: diameter: 33-42 Ám; process length: 5-10 Ám; wall thickness up to 1.5 Ám, usually 1Ám or less. 17 specimens were measured.
Supplemental description: Head, 1993, p.27
Cyst skolochorate. Processes non-tabular, about 8 Ám long, characteristically solid, with granulate surface, and tapering to sinuous points. Processes arise from circular bases up to about 2.6 Ám wide but some thinner processes with bases of about 1.3 Ám also observed. Wall thickness less than 1 Ám. Periphragm distinctly microreticulate with lumina about 0.5 Ám wide or less and muri about 0.3 Ám wide. A single torn specimen seen.
Affinities:
Head et al. 1989, p. 459: The long acuminate solid, nonfibrous processes and nonfibrous microreticulate surface distinguish this species from 'typical' Operculodinium taxa, including the type species. These characters possibly reflect a fundamentally different structural pattern between O.?eirikianum and typical species of Operculodinium. O. longispinigerum Matsuoka, 1983 from the Miocene of Japan has a smooth to granulate wall surface, rather than a microreticulate wall surface, as found in O. ?eirikianum. Both O. echigoense Matsuoka, 1983 and O. walli Matsuoka, 1983 have capitate or bifid process terminations, compared to the tapering, acuminate process terminations of O. ?eirikianum.
Head et al., 1989, questionably included this species in Operculodinium.
Holotype: Head et al., 1989, pl.4, figs.11,15-16
Locus typicus: Eirik Ridge, Labrador Sea, S of Greenland
Stratum typicum: Late Miocene-Early Pliocene
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Operculodinium eirikianum Head et al., 1989b, emend. Head, 1997. According to Head (1997), Operculodinium eirikianum is skolochorate with spherical central body. Wall consists of pedium (less than 0.2 µm thick) and thicker luxuria forming an irregular microreticulum of sinuous undulating muri about 0.2-0.3 µm wide that enclose lumina, mostly of about 0.5 µm or less in diameter. Processes solid, nonfibrous, with circular cross section for most of their length, may have scattered fine granules over surface, often become sinuous distally, and taper gradually to an acuminate tip. Process distribution apparently non-tabular. Each process arises either directly from surface or from a ridge that is low, short (about 6 µm or less), narrow, and straight or slightly arcuate. Archeopyle precingular type P(3"), deltacamerate with smooth margins, angles well defined. No accessory sutures. Operculum free. Size: diameter central body 33-42 µm, process length 5-10 µm, wall thickness up to 1.5 µm, but usually 1 µm or less.
--------------------------------------------------
Original description: Head et al. 1989, p. 459
Diagnosis: Cysts skolochorate, having a spherical body and nontabular processes. Cyst wall apparently single layered; solid and nonfibrous and has a prominently microreticulate surface. Processes are solid, circular in cross section, nonfibrous and taper gradually to an acuminate tip. They are often sinuous towards the tips and may have scattered fine granules over their surface. Archeopyle precingular Type P (presumably by loss of paraplate 3''). Operculum free.
Dimensions: Range: diameter: 33-42 Ám; process length: 5-10 Ám; wall thickness up to 1.5 Ám, usually 1Ám or less. 17 specimens were measured.
Supplemental description: Head, 1993, p.27
Cyst skolochorate. Processes non-tabular, about 8 Ám long, characteristically solid, with granulate surface, and tapering to sinuous points. Processes arise from circular bases up to about 2.6 Ám wide but some thinner processes with bases of about 1.3 Ám also observed. Wall thickness less than 1 Ám. Periphragm distinctly microreticulate with lumina about 0.5 Ám wide or less and muri about 0.3 Ám wide. A single torn specimen seen.
Affinities:
Head et al. 1989, p. 459: The long acuminate solid, nonfibrous processes and nonfibrous microreticulate surface distinguish this species from 'typical' Operculodinium taxa, including the type species. These characters possibly reflect a fundamentally different structural pattern between O.?eirikianum and typical species of Operculodinium. O. longispinigerum Matsuoka, 1983 from the Miocene of Japan has a smooth to granulate wall surface, rather than a microreticulate wall surface, as found in O. ?eirikianum. Both O. echigoense Matsuoka, 1983 and O. walli Matsuoka, 1983 have capitate or bifid process terminations, compared to the tapering, acuminate process terminations of O. ?eirikianum.