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Omatia montgomeryi
Omatia montgomeryi Cookson and Eisenack, 1958; emend. Stover and Helby, 1987
Holotype: Cookson and Eisenack, 1958, pl.8, fig.8
Locus typicus: Omai, Papua
Stratum typicum: Late Jurassic
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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.
Omatia montgomeryi Cookson and Eisenack, 1958, emend. Stover and Helby, 1987b. Omatia montgomeryi has solid, generally simple, rarely bifurcate processes, which tend to be wider in the apical and antapical areas and are nearly always absent in the paracingular region. The linearly aligned processes are parasutural, occur in single or closely spaced double rows, and both single and double rows of processes may occur along the same linear feature. The antapical paraplate is always on the posterior ventral surface. Size: 76-124 x 29-45 µm.
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Original description: Cookson and Eisenack, 1958, p. 60
Shell slightly pointed or with short truncate neck at one end rounded at the other; surface granular, covered more or less completely by a narrow and delicate membrane which is supported by short, thin, simple or bifurcate processes which tend to be arranged in longitudinal rows. The membrane is widest and the processes are most numerous at the two ends of the shell.
Emended description: Stover and Helby, 1987, p. 152
Cysts proximate, narrowly ellipsoidal with a short, blunt apical projection
formed by a protrusion of the autophragm and ectophragm (Fig.3E,F). A hole or circular depression may occur at the tip of the projection (Fig.2A,C). Antapical end broadly rounded or truncate. Autophragm thicker than the ectophragm, appearing finely granulate to punctogranulate in transmitted light (Fig.3K,L). Outer surface of the autophragm composed of minute (generally less than 0.5Ám), variously shaped, densely packed projections (Fig.2D,E). Autophragm surface also with solid, generally simple, rarely branched, processes (Figs 2D,3A-D,G,H,J) whose blunt tips merge with the thin (less than 1 Ám), transparent, essentially featureless ectophragm (Fig.2A,D). Process supported ectophragm frequently folded or wrinkled and may contact the autophragm in the process free areas.
Processes about 0.5-2.5Ám wide, 1.5-8Ám long (usually less than 4Ám), subcircular to roundly polygonal in cross section, and occur as isolated projections, in groups of 3-8 (usually in the apical area and in the midventral area of the hypocyst near the antapex), and in generally longitudinal, less commonly transverse or oblique, parasutural rows (Figs 3A-D,K, 4A-E). Aligned processes may be in single or in double rows. The processes in one row may be opposite those in the other, or alternate with those in the other row, but not necessarily at uniform intervals (Fig.5A-C). Both single and double rows of processes may occur along the same parasutural feature. Processes near and more or less parallel to parasutures when the latter are present in the autophragm (Figs 2D,E, 3K); if double rows of processes present, parasutures occur between them. Paratabulation expressed mainly by rows of parasutural processes formula of 4', 4'', Xc, 5''', 1p, 1'''' (Fig.6A,B). However, only a part of the paratabulation may be evident. Paratabulation usually more complete on the dorsal surface than on the ventral surface, where it is reduced relative to the 'standard' gonyaulacaceaen pattern. Less appearent, generally vague indications of paratabulation such as folds, indentations, and thickenings of the ectophragm, in addition to the parasutural features, may be present. On some specimens the paracingulum expressed only by those features, but more commonly its position can be interpreted as the equatorial area between ends of the precingular and postcingular processes. Antapical paraplate (1'''') situated in the posterior ventral surface, not at the antapex. Parasulcus generally not expressed, however on an occasional specimen the posterior part of the parasulcus outlined by the adjacent boundaries. No definitive mode of archaeopyle determined, and it is doubtful if a single or variable type archaeopyle developed. Splitting of the autophragm and seperation of one part from another evidently occuring almost anywhere on the cyst, and specimens with intact epicyst (and without indications of the archaeopyle) but missing an appreciable part of the hypocyst common. Lines of seperation straight or ragged, following paraplate boundaries, or crossing them indiscriminately.
Holotype: Cookson and Eisenack, 1958, pl.8, fig.8
Locus typicus: Omai, Papua
Stratum typicum: Late Jurassic
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Omatia montgomeryi Cookson and Eisenack, 1958, emend. Stover and Helby, 1987b. Omatia montgomeryi has solid, generally simple, rarely bifurcate processes, which tend to be wider in the apical and antapical areas and are nearly always absent in the paracingular region. The linearly aligned processes are parasutural, occur in single or closely spaced double rows, and both single and double rows of processes may occur along the same linear feature. The antapical paraplate is always on the posterior ventral surface. Size: 76-124 x 29-45 µm.
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Original description: Cookson and Eisenack, 1958, p. 60
Shell slightly pointed or with short truncate neck at one end rounded at the other; surface granular, covered more or less completely by a narrow and delicate membrane which is supported by short, thin, simple or bifurcate processes which tend to be arranged in longitudinal rows. The membrane is widest and the processes are most numerous at the two ends of the shell.
Emended description: Stover and Helby, 1987, p. 152
Cysts proximate, narrowly ellipsoidal with a short, blunt apical projection
formed by a protrusion of the autophragm and ectophragm (Fig.3E,F). A hole or circular depression may occur at the tip of the projection (Fig.2A,C). Antapical end broadly rounded or truncate. Autophragm thicker than the ectophragm, appearing finely granulate to punctogranulate in transmitted light (Fig.3K,L). Outer surface of the autophragm composed of minute (generally less than 0.5Ám), variously shaped, densely packed projections (Fig.2D,E). Autophragm surface also with solid, generally simple, rarely branched, processes (Figs 2D,3A-D,G,H,J) whose blunt tips merge with the thin (less than 1 Ám), transparent, essentially featureless ectophragm (Fig.2A,D). Process supported ectophragm frequently folded or wrinkled and may contact the autophragm in the process free areas.
Processes about 0.5-2.5Ám wide, 1.5-8Ám long (usually less than 4Ám), subcircular to roundly polygonal in cross section, and occur as isolated projections, in groups of 3-8 (usually in the apical area and in the midventral area of the hypocyst near the antapex), and in generally longitudinal, less commonly transverse or oblique, parasutural rows (Figs 3A-D,K, 4A-E). Aligned processes may be in single or in double rows. The processes in one row may be opposite those in the other, or alternate with those in the other row, but not necessarily at uniform intervals (Fig.5A-C). Both single and double rows of processes may occur along the same parasutural feature. Processes near and more or less parallel to parasutures when the latter are present in the autophragm (Figs 2D,E, 3K); if double rows of processes present, parasutures occur between them. Paratabulation expressed mainly by rows of parasutural processes formula of 4', 4'', Xc, 5''', 1p, 1'''' (Fig.6A,B). However, only a part of the paratabulation may be evident. Paratabulation usually more complete on the dorsal surface than on the ventral surface, where it is reduced relative to the 'standard' gonyaulacaceaen pattern. Less appearent, generally vague indications of paratabulation such as folds, indentations, and thickenings of the ectophragm, in addition to the parasutural features, may be present. On some specimens the paracingulum expressed only by those features, but more commonly its position can be interpreted as the equatorial area between ends of the precingular and postcingular processes. Antapical paraplate (1'''') situated in the posterior ventral surface, not at the antapex. Parasulcus generally not expressed, however on an occasional specimen the posterior part of the parasulcus outlined by the adjacent boundaries. No definitive mode of archaeopyle determined, and it is doubtful if a single or variable type archaeopyle developed. Splitting of the autophragm and seperation of one part from another evidently occuring almost anywhere on the cyst, and specimens with intact epicyst (and without indications of the archaeopyle) but missing an appreciable part of the hypocyst common. Lines of seperation straight or ragged, following paraplate boundaries, or crossing them indiscriminately.