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Kisselovia columna
Kisselovia columna Michoux, 1988
Now Charlesdowniea. Originally Kisselovia, subsequently (and now) Charlesdowniea.
Holotype: Michoux, 1988, pl.1, figs.2-3
Locus typicus: Donzacq claypit, France
Stratum typicum: Early Eocene
Original diagnosis: Michoux, 1988, p.28
Circumcavate peridinioid cyst, dorsoventrally compressed. Penitabular ornamentation of cylindrical processes supporting an ectophragmal membrane, the latter preferentially developed at ambital margin. Paratabulation pattern is paraquadra. 2a archeopyle of the W. meckelfeldensis type; periarcheopyle longer than endoarcheopyle, opercula free.
Original description: Michoux, 1988, p. 28
Peridinioid cyst with one apical, two lateral and two antapical horns, the right of which is reduced; horn development variable. The ambitus is rectilinear between adjacent horns, except between the antapical horns where it is strongly concave. The periphragm is smooth; the endophragm is slightly granular. The latter is subcircular to ellipsoidal in outline, separated from the periphragm in dorsoventral view by a narrow but continuous pericoel. Because of its delicate nature and preferential development over the cyst margins, the distribution of the ornamentation is diff1cult to determine under light microscopy, and is best observed on SEM photomicrogaphs. It is well-displayed on the specimens illustrated on Plate 2, figs. 3, 5 (ventral surface), and 4 (dorsal surface). Processes are short (up to 5 ,um in length), cylindrical, arranged in penitabular complexes, and support arcuate ectophragmal membranes. They are rare or absent over the adcingular margin of the large mid-dorsal pre- and postcingular paraplates 4" and 3""". This feature is also obvious on the specimen illustrated by Williams and Bujak (1977, pl. 3, fig. 1). Ectophragm development is minimal over the midventral and mid-dorsal areas of the cyst, where it can be reduced to a narrow strip. Paraplate 2a bears an arcuate membrane whose concavity is oriented towards the paracingulum. Paraplate 3" is entirely covered by a subtriangular membrane. Paraplate 1" is five-sided and bears a ribbon-like membrane over its perimeter. The lateral paraplates of the ventral epicyst (2", 2", and 4", 6") show linear complexes of processes supporting ribbon-like trabeculae. The longitudinal development of the trabeculae over these pairs is such that they are almost in contact (see Plate 2, fig. 5). These boundaries abut the lateral sides of 1", revealing a para ventral paratabulation pattern. Dorsally, the paratabulation pattern is quadra, with 4" decidedly wider than 2a. The archeopyle is of the Wetzeliella meckelfeldensis type, nearly as wide at its base as it is high, with the periarcheopyle higher than the endoarcheopyle. Opercula are free.
Dimensions. Pericyst. Length: 104 (113) 121 Ám. Width: 90 (108) 124 Ám. Holotype: 121 x 124 Ám. Archeopyle. Length: 20 (21) 24 Ám. Width: 22 (27) 29 Ám. Holotype: 21 x 27 Ám. Processes: up to 4 Ám.
Affinities:
Michoux, 1988, p. 28: Kisselovia columna is similar to K. clathrata (Eisenack) Lentin & Williams, but differs in shape and details of ornamentation. The right antapical horn is more reduced in K clathrata, imparting a more rhombic outline to the cyst. The sides of the cyst on K. clathrata are also more convex, and the pericoel larger. The ectophragm of K. clathrata is developed by fusion of adjacent process tips, not developed into a membrane (see Eisenack, 1954, text-fig. 2). Kisselovia edwardsii (Wilson) Stover & Evitt has processes restricted to the periphery of the cyst.
Now Charlesdowniea. Originally Kisselovia, subsequently (and now) Charlesdowniea.
Holotype: Michoux, 1988, pl.1, figs.2-3
Locus typicus: Donzacq claypit, France
Stratum typicum: Early Eocene
Original diagnosis: Michoux, 1988, p.28
Circumcavate peridinioid cyst, dorsoventrally compressed. Penitabular ornamentation of cylindrical processes supporting an ectophragmal membrane, the latter preferentially developed at ambital margin. Paratabulation pattern is paraquadra. 2a archeopyle of the W. meckelfeldensis type; periarcheopyle longer than endoarcheopyle, opercula free.
Original description: Michoux, 1988, p. 28
Peridinioid cyst with one apical, two lateral and two antapical horns, the right of which is reduced; horn development variable. The ambitus is rectilinear between adjacent horns, except between the antapical horns where it is strongly concave. The periphragm is smooth; the endophragm is slightly granular. The latter is subcircular to ellipsoidal in outline, separated from the periphragm in dorsoventral view by a narrow but continuous pericoel. Because of its delicate nature and preferential development over the cyst margins, the distribution of the ornamentation is diff1cult to determine under light microscopy, and is best observed on SEM photomicrogaphs. It is well-displayed on the specimens illustrated on Plate 2, figs. 3, 5 (ventral surface), and 4 (dorsal surface). Processes are short (up to 5 ,um in length), cylindrical, arranged in penitabular complexes, and support arcuate ectophragmal membranes. They are rare or absent over the adcingular margin of the large mid-dorsal pre- and postcingular paraplates 4" and 3""". This feature is also obvious on the specimen illustrated by Williams and Bujak (1977, pl. 3, fig. 1). Ectophragm development is minimal over the midventral and mid-dorsal areas of the cyst, where it can be reduced to a narrow strip. Paraplate 2a bears an arcuate membrane whose concavity is oriented towards the paracingulum. Paraplate 3" is entirely covered by a subtriangular membrane. Paraplate 1" is five-sided and bears a ribbon-like membrane over its perimeter. The lateral paraplates of the ventral epicyst (2", 2", and 4", 6") show linear complexes of processes supporting ribbon-like trabeculae. The longitudinal development of the trabeculae over these pairs is such that they are almost in contact (see Plate 2, fig. 5). These boundaries abut the lateral sides of 1", revealing a para ventral paratabulation pattern. Dorsally, the paratabulation pattern is quadra, with 4" decidedly wider than 2a. The archeopyle is of the Wetzeliella meckelfeldensis type, nearly as wide at its base as it is high, with the periarcheopyle higher than the endoarcheopyle. Opercula are free.
Dimensions. Pericyst. Length: 104 (113) 121 Ám. Width: 90 (108) 124 Ám. Holotype: 121 x 124 Ám. Archeopyle. Length: 20 (21) 24 Ám. Width: 22 (27) 29 Ám. Holotype: 21 x 27 Ám. Processes: up to 4 Ám.
Affinities:
Michoux, 1988, p. 28: Kisselovia columna is similar to K. clathrata (Eisenack) Lentin & Williams, but differs in shape and details of ornamentation. The right antapical horn is more reduced in K clathrata, imparting a more rhombic outline to the cyst. The sides of the cyst on K. clathrata are also more convex, and the pericoel larger. The ectophragm of K. clathrata is developed by fusion of adjacent process tips, not developed into a membrane (see Eisenack, 1954, text-fig. 2). Kisselovia edwardsii (Wilson) Stover & Evitt has processes restricted to the periphery of the cyst.