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Lunatadinium dissolutum
Lunatadinium *dissolutum Brideaux and McIntyre, 1973, p.396-397,400-401, pl.1, figs.1-13.
Taxonomic junior synonym: Pylomacystion californicum (name not validly published), according to Brideaux and McIntyre (1973, p.400).
Holotype: Brideaux and McIntyre, 1973, pl.1, figs.3-4; Fensome et al., 1993a, figs.1-2 - p.1129.
Age: Hauterivian-Mid Albian.
Original description: Brideaux and McIntyre, 1973, p.397, 400
The proximate cyst is circular to subcircular in outline, dorso-ventrally flattened, and is found with either the dorsal or ventral surface uppermost Apical and antapical horns are absent The single-layered cyst wall is about 1.0 µm thick on the dorsal side and slightly thinner on the ventral side The cyst wall often is folded and breaks readily on the thinner ventral side The wall surface is smooth or faintly scabrate with small granular sculpture elements which are less than 0.5 µm in diameter.
A cingulum, 4.0 to 7.0 µm wide, is visible on the dorsal surface of some specimens It is delineated on the anterior margin by the archeopyle and on the posterior margin by a low, narrow ridge ([Brideaux and McIntyre, 1973] Plate 1, Figs 1 and 4) Rarely, two parallel ridges outline the cingulum ([Brideaux and McIntyre, 1973] Plate 1, Fig 8) and two specimens ([Brideaux and McIntyre, 1973] Plate 1, Figs 11 and 12) show slight indentations at the lateral position of the cingulum A sulcus cannot be identified definitely, although some specimens show a faint concavity, framed by folds, in the probable sulcal area ([Brideaux and McIntyre, 1973] Plate 1, Fig 12).
The archeopyle, which is large, elliptical to circular and precingular, is the type 3P of Evitt (1967) and occupies almost all of the dorsal surface of the epitract The rounded form of the archeopyle suggests that the sutures may not have followed exactly the reflected plate boundaries The operculum almost always is detached and is usually found within the autocoel ([Brideaux and McIntyre, 1973] Plate 1, Figs 2, 3 and 13) It apparently consists of the precingular reflected plates 2", 3" and 4", which separate as a single unit ([Brideaux and McIntyre, 1973] Plate 1, Fig 10), and no accessory archeopyle sutures are developed A central apical peak commonly present on the operculum represents part of the outline of reflected plate 3". No further indications of reflected tabulation can be deduced from examination of this species under the light microscope.
Most specimens exhibit some breakage and many lose part of the ventral side and the apical region of the cyst The dorsal and ventral hypotract and two horn-like strips, which are possibly reflected plates 1" and 5" of the dorsal epitract, remain ([Brideaux and McIntyre, 1973] Plate 1, Figs 1, 6, 7, 9 and 12) The missing ventral portion has never been recognized separately on the slide This breakage is considered mechanical, or perhaps chemical, in origin and does not support an interpretation of a more complex archeopyle.
Size.
Holotype: length 58 µm, width 62 µm. Range of 100 specimens length 41-76 µm, width 41-69 µm.
Taxonomic junior synonym: Pylomacystion californicum (name not validly published), according to Brideaux and McIntyre (1973, p.400).
Holotype: Brideaux and McIntyre, 1973, pl.1, figs.3-4; Fensome et al., 1993a, figs.1-2 - p.1129.
Age: Hauterivian-Mid Albian.
Original description: Brideaux and McIntyre, 1973, p.397, 400
The proximate cyst is circular to subcircular in outline, dorso-ventrally flattened, and is found with either the dorsal or ventral surface uppermost Apical and antapical horns are absent The single-layered cyst wall is about 1.0 µm thick on the dorsal side and slightly thinner on the ventral side The cyst wall often is folded and breaks readily on the thinner ventral side The wall surface is smooth or faintly scabrate with small granular sculpture elements which are less than 0.5 µm in diameter.
A cingulum, 4.0 to 7.0 µm wide, is visible on the dorsal surface of some specimens It is delineated on the anterior margin by the archeopyle and on the posterior margin by a low, narrow ridge ([Brideaux and McIntyre, 1973] Plate 1, Figs 1 and 4) Rarely, two parallel ridges outline the cingulum ([Brideaux and McIntyre, 1973] Plate 1, Fig 8) and two specimens ([Brideaux and McIntyre, 1973] Plate 1, Figs 11 and 12) show slight indentations at the lateral position of the cingulum A sulcus cannot be identified definitely, although some specimens show a faint concavity, framed by folds, in the probable sulcal area ([Brideaux and McIntyre, 1973] Plate 1, Fig 12).
The archeopyle, which is large, elliptical to circular and precingular, is the type 3P of Evitt (1967) and occupies almost all of the dorsal surface of the epitract The rounded form of the archeopyle suggests that the sutures may not have followed exactly the reflected plate boundaries The operculum almost always is detached and is usually found within the autocoel ([Brideaux and McIntyre, 1973] Plate 1, Figs 2, 3 and 13) It apparently consists of the precingular reflected plates 2", 3" and 4", which separate as a single unit ([Brideaux and McIntyre, 1973] Plate 1, Fig 10), and no accessory archeopyle sutures are developed A central apical peak commonly present on the operculum represents part of the outline of reflected plate 3". No further indications of reflected tabulation can be deduced from examination of this species under the light microscope.
Most specimens exhibit some breakage and many lose part of the ventral side and the apical region of the cyst The dorsal and ventral hypotract and two horn-like strips, which are possibly reflected plates 1" and 5" of the dorsal epitract, remain ([Brideaux and McIntyre, 1973] Plate 1, Figs 1, 6, 7, 9 and 12) The missing ventral portion has never been recognized separately on the slide This breakage is considered mechanical, or perhaps chemical, in origin and does not support an interpretation of a more complex archeopyle.
Size.
Holotype: length 58 µm, width 62 µm. Range of 100 specimens length 41-76 µm, width 41-69 µm.