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Leptodinium cancellatum
Leptodinium cancellatum Brideaux and McIntyre, 1975
Holotype: Brideaux and McIntyre, 1975, pl. 5, fig. 8; Jan du Chene et al., 1986, pl.73, figs.5-6
Locus typicus: Horton River, District of Machenzie, Canada
Stratum typicum: Middle Albian
Original diagnosis: Brideaux and McIntyre, 1975, p. 21
Circular or subcircular outline; length to width ratio close to 1.0. Wall two-layered, the periphragm forming low sutural ridges reflecting a tabulation of 4", 6", 6c, 5""", 1"""", 1p, 5s, and also forming the intratabular apiculate to vermiculate sculpture. Reflected plate 1" elongate and narrow, 4" considerably larger than 1". Cingulum offset 1 to 1-1/2 cingular widths; sulcus nearly straight, with reflected sulcul tabulation often developed. Archeopyle precingular, formed by loss of reflected plate 3"; operculum detached.
Original description: Brideaux and McIntyre, 1975, p. 21-22
The cyst outline is circular or subcircular. The ratio of epitract to hypotract length is close to 1.0. Both apex and antapex are rounded. The cyst wall is two layered. The endophragm is smooth and thin, less than 0.5 Ám thick in optical section. The periphragm is about 1.0 Ám thick in optical section and forms the low sutural crests and intratabular sculpture. The two layers are in contact except at the sutures and the intratabular ridges. The periphragm is finely granular between the major sculpture. Intratabular sculpture is variable, even on a given specimen, and ranges from granulate to vermiculate or vermiculate-reticulate forming a trellis-like pattern. The intratabular sculpture may connect with the sutural ridges.
Intratabular sculpture is less than 1.0 Ám in height and from 0.5 to 2.0 Ám in width.
The archeopyle is precingular and formed by the loss of reflected plate 3". The operculum is detached and rounded-trapezoidal in shape.
The cingulum is well marked by a pair of cingular ridges, which are similar to the sutural ridges and connect with them. Cross-sutures delimit six precingular reflected plates. The cingulum is from 4.0 to 7.0 Ám wide, sinistral, and displaced one to one and one-half cingular widths. The sulcus is narrow anteriorly, where the reflected anterior sulcal plate adjoins 1", and widens posteriorly to meet the reflected antapical plate 1"""". Some, or all, of the sulcal reflected plates (anterior sulcal, left anterior sulcal, right sulcal, left sulcal and posterior sulcal) are visible on a given specimen. A central area located between the reflected anterior and posterior sulcal plates is probably the reflected site of the insertion of the longitudinal flagellum. Reflected tabulation correspond to the formula 4", 6", 6c, 6""", 1, 5s, 1"""". Reflected plate 1" is narrow posteriorly and is widest just below the apex; reflected plate 4" is much larger than 1"; reflected plate lp is trapezoidal in shape. The reflected tabulation is outlined by low, narrow, sutural ridges, 1-2 Ám wide, by irregularly dissected sutural ridges, or by sutural rows of basally connected pila or coni, 1-2 Ám high. The sutures often are crenulated.
Dimensions: Length, 57-77 Ám; width, 52-67 Ám.
Affinities:
Brideaux and McIntyre, 1975, p. 22: The intratabular sculpture of Leptodinium cancellatum series to distinguish the species from others described in the literature.
Holotype: Brideaux and McIntyre, 1975, pl. 5, fig. 8; Jan du Chene et al., 1986, pl.73, figs.5-6
Locus typicus: Horton River, District of Machenzie, Canada
Stratum typicum: Middle Albian
Original diagnosis: Brideaux and McIntyre, 1975, p. 21
Circular or subcircular outline; length to width ratio close to 1.0. Wall two-layered, the periphragm forming low sutural ridges reflecting a tabulation of 4", 6", 6c, 5""", 1"""", 1p, 5s, and also forming the intratabular apiculate to vermiculate sculpture. Reflected plate 1" elongate and narrow, 4" considerably larger than 1". Cingulum offset 1 to 1-1/2 cingular widths; sulcus nearly straight, with reflected sulcul tabulation often developed. Archeopyle precingular, formed by loss of reflected plate 3"; operculum detached.
Original description: Brideaux and McIntyre, 1975, p. 21-22
The cyst outline is circular or subcircular. The ratio of epitract to hypotract length is close to 1.0. Both apex and antapex are rounded. The cyst wall is two layered. The endophragm is smooth and thin, less than 0.5 Ám thick in optical section. The periphragm is about 1.0 Ám thick in optical section and forms the low sutural crests and intratabular sculpture. The two layers are in contact except at the sutures and the intratabular ridges. The periphragm is finely granular between the major sculpture. Intratabular sculpture is variable, even on a given specimen, and ranges from granulate to vermiculate or vermiculate-reticulate forming a trellis-like pattern. The intratabular sculpture may connect with the sutural ridges.
Intratabular sculpture is less than 1.0 Ám in height and from 0.5 to 2.0 Ám in width.
The archeopyle is precingular and formed by the loss of reflected plate 3". The operculum is detached and rounded-trapezoidal in shape.
The cingulum is well marked by a pair of cingular ridges, which are similar to the sutural ridges and connect with them. Cross-sutures delimit six precingular reflected plates. The cingulum is from 4.0 to 7.0 Ám wide, sinistral, and displaced one to one and one-half cingular widths. The sulcus is narrow anteriorly, where the reflected anterior sulcal plate adjoins 1", and widens posteriorly to meet the reflected antapical plate 1"""". Some, or all, of the sulcal reflected plates (anterior sulcal, left anterior sulcal, right sulcal, left sulcal and posterior sulcal) are visible on a given specimen. A central area located between the reflected anterior and posterior sulcal plates is probably the reflected site of the insertion of the longitudinal flagellum. Reflected tabulation correspond to the formula 4", 6", 6c, 6""", 1, 5s, 1"""". Reflected plate 1" is narrow posteriorly and is widest just below the apex; reflected plate 4" is much larger than 1"; reflected plate lp is trapezoidal in shape. The reflected tabulation is outlined by low, narrow, sutural ridges, 1-2 Ám wide, by irregularly dissected sutural ridges, or by sutural rows of basally connected pila or coni, 1-2 Ám high. The sutures often are crenulated.
Dimensions: Length, 57-77 Ám; width, 52-67 Ám.
Affinities:
Brideaux and McIntyre, 1975, p. 22: The intratabular sculpture of Leptodinium cancellatum series to distinguish the species from others described in the literature.