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Charlesdowniea coleothrypta
Charlesdowniea coleothrypta, (Williams and Downie, 1966), Lentin and Vozzhennikova, 1989
Originally Wetzeliella, subsequently Kisselovia, thirdly (and now) Charlesdowniea.
Holotype: Williams and Downie, 1966, pl.18, fig.8, text-fig.47; Bujak et al., 1980, pl.12, figs.7-8
Locus typicus: London Clay, Sheppey, Kent, England
Stratum typicum: Early Eocene
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Original description as Wetzeliella (Wetzeliella) coleothrypta: [Williams and Downie, 1966, p. 185-186]:
Diagnosis:
Thin walled periphragm characteristic pentagonal outline with each angle produced into horns, one apical, two lateral and two antapical; left antapical horn generally reduced.
Pericoel totally enclosing endophragm.
Processes arising from periphragm, hollow, connecting with pericoel. Distally processes of individual simulate complex united by finely perforate membrane assuming outline of underlying plate and extending over that plate as replica of it. Processes commonly absent from pre- and postcingular plates on side lying nearest to cingulum.
Reflected tabulation of 4', 3a, 7'', 5c, 5''', 2'''', 3-4s.
Description (annotated):
The periphragm of W. coleothrypta has an outline approaching W. similis on the one hand and W. articulata on the other.
The apical horn has a pointed apex; the lateral horns are indented distally due to the transverse cingulum crossing from the dorsal to the ventral surface at these two places.
The slender, simple, or occasionally branched processes are intratabular, arising from just within the plate boundary and usually forming a simulate complex on each plate. The general rule that the longer the processes, the further away they are from the horns, is found to be true for this species.
The plates, interpreted from the simulate complexes, show considerable variation in size. Of the apicals, plate 1' is by far the largest and has a trapezoid outline: plates 2' and 4' are lateral in position and are narrow, being represented by a single row of processes; whilst the dorsal plate 3' is intermediate in size between 1' and 4'. The anterior intercalary plates likewise vary in size and are dorsal in position. Plates 1a and 3a are elongate, narrowing apically, whereas plate 2a, the loss of which forms the archaeopyle, is trapezoid, with processes absent from its equatorial boundary. The seven precingulars show extreme variation. Plates 1'' and 7'' are of comparable size with an almost triangular outline. Plates 2'' and 6'' are extremely narrow and are represented by a singly row of processes running along the lateral margin. On the dorsal surface, the three plates 3'', 4'', and 5'' are wider than the others and do not extend as far towards the apex, being restricted because of the anterior intercalaries. Plate 4'' is the widest of the precingular series. The circular cingulum comprises five plates, three on the dorsal surface, two on the ventral. Each plate has a single row of processes that are united distally as in W. clathrata. Of the postcingulars, plates 1''' and 5''' on the ventral surface are of comparable size and shape (see Fig. 47), whilst plates 2''' and 4''' are smaller though of not dissimilar outline. The widest of the postcingulars is plate 3''', which usually has no processes on the side adjacent to the transverse cingulum. This is also frequently true of most of the pre- and postcingular plates. The two antapical plates are dorsally situated.
The sulcus is considerably expanded on the hypotract and extends to the distal extremities of the antapical horns. There can be three or four sulcal plates, of which the most posterior is the largest and has a rhomboidal shape. Only one sulcal plate is present on the epitract. The tabulation is always clearly shown and easily decipherable.
The width of the pericoel has no bearing on the thickness of the capsule wall, in this or any other species of Wetzeliella. The capsule of W. coleothrypta may be slightly granular;
it possesses an archaeopyle which is in line with that of the periphragm and appears to be intercalary. The operculum of the archeopyle is often found lying within the capsule.
Dimensions:
Holotype: periphragm length 122 µm; breadth 110 µm. Capsule length 69 µm; breadth 61.5 µm.
Observed range: outer shell length 112.5-157 µm; breadth 102.5-142 µm. Capsule length 66-106 µm; breadth 67-97 µm. Processes up to 15 µm long. Number of specimens measured, 6.
Affinities:
Of the described species of Wetzeliella, only W. clathrata has processes united distally. However, whereas in W. clathrata the processes are united so as to give lists or bars of restricted width, in W. coleothrypta, the membrane assumes outline of the plate and passes completely over it, forming an outer umbrella. The two species can therefore be easily distinguished.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Charlesdowniea coleothrypta (Williams and Downie, 1966b) Lentin and Vozzhennikova, 1989, has a membranous ectophragm, which usually extends over most of the paraplate, although in the type material some specimens show a similar development to that of C. columna. The holotype has an epeliform archeopyle.
Size: Pericyst length 112.5-157 µm, width 102.5-142 µm, endocyst length 66-106 µm, width 67-97 µm.
Originally Wetzeliella, subsequently Kisselovia, thirdly (and now) Charlesdowniea.
Holotype: Williams and Downie, 1966, pl.18, fig.8, text-fig.47; Bujak et al., 1980, pl.12, figs.7-8
Locus typicus: London Clay, Sheppey, Kent, England
Stratum typicum: Early Eocene
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Wetzeliella (Wetzeliella) coleothrypta: [Williams and Downie, 1966, p. 185-186]:
Diagnosis:
Thin walled periphragm characteristic pentagonal outline with each angle produced into horns, one apical, two lateral and two antapical; left antapical horn generally reduced.
Pericoel totally enclosing endophragm.
Processes arising from periphragm, hollow, connecting with pericoel. Distally processes of individual simulate complex united by finely perforate membrane assuming outline of underlying plate and extending over that plate as replica of it. Processes commonly absent from pre- and postcingular plates on side lying nearest to cingulum.
Reflected tabulation of 4', 3a, 7'', 5c, 5''', 2'''', 3-4s.
Description (annotated):
The periphragm of W. coleothrypta has an outline approaching W. similis on the one hand and W. articulata on the other.
The apical horn has a pointed apex; the lateral horns are indented distally due to the transverse cingulum crossing from the dorsal to the ventral surface at these two places.
The slender, simple, or occasionally branched processes are intratabular, arising from just within the plate boundary and usually forming a simulate complex on each plate. The general rule that the longer the processes, the further away they are from the horns, is found to be true for this species.
The plates, interpreted from the simulate complexes, show considerable variation in size. Of the apicals, plate 1' is by far the largest and has a trapezoid outline: plates 2' and 4' are lateral in position and are narrow, being represented by a single row of processes; whilst the dorsal plate 3' is intermediate in size between 1' and 4'. The anterior intercalary plates likewise vary in size and are dorsal in position. Plates 1a and 3a are elongate, narrowing apically, whereas plate 2a, the loss of which forms the archaeopyle, is trapezoid, with processes absent from its equatorial boundary. The seven precingulars show extreme variation. Plates 1'' and 7'' are of comparable size with an almost triangular outline. Plates 2'' and 6'' are extremely narrow and are represented by a singly row of processes running along the lateral margin. On the dorsal surface, the three plates 3'', 4'', and 5'' are wider than the others and do not extend as far towards the apex, being restricted because of the anterior intercalaries. Plate 4'' is the widest of the precingular series. The circular cingulum comprises five plates, three on the dorsal surface, two on the ventral. Each plate has a single row of processes that are united distally as in W. clathrata. Of the postcingulars, plates 1''' and 5''' on the ventral surface are of comparable size and shape (see Fig. 47), whilst plates 2''' and 4''' are smaller though of not dissimilar outline. The widest of the postcingulars is plate 3''', which usually has no processes on the side adjacent to the transverse cingulum. This is also frequently true of most of the pre- and postcingular plates. The two antapical plates are dorsally situated.
The sulcus is considerably expanded on the hypotract and extends to the distal extremities of the antapical horns. There can be three or four sulcal plates, of which the most posterior is the largest and has a rhomboidal shape. Only one sulcal plate is present on the epitract. The tabulation is always clearly shown and easily decipherable.
The width of the pericoel has no bearing on the thickness of the capsule wall, in this or any other species of Wetzeliella. The capsule of W. coleothrypta may be slightly granular;
it possesses an archaeopyle which is in line with that of the periphragm and appears to be intercalary. The operculum of the archeopyle is often found lying within the capsule.
Dimensions:
Holotype: periphragm length 122 µm; breadth 110 µm. Capsule length 69 µm; breadth 61.5 µm.
Observed range: outer shell length 112.5-157 µm; breadth 102.5-142 µm. Capsule length 66-106 µm; breadth 67-97 µm. Processes up to 15 µm long. Number of specimens measured, 6.
Affinities:
Of the described species of Wetzeliella, only W. clathrata has processes united distally. However, whereas in W. clathrata the processes are united so as to give lists or bars of restricted width, in W. coleothrypta, the membrane assumes outline of the plate and passes completely over it, forming an outer umbrella. The two species can therefore be easily distinguished.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Charlesdowniea coleothrypta (Williams and Downie, 1966b) Lentin and Vozzhennikova, 1989, has a membranous ectophragm, which usually extends over most of the paraplate, although in the type material some specimens show a similar development to that of C. columna. The holotype has an epeliform archeopyle.
Size: Pericyst length 112.5-157 µm, width 102.5-142 µm, endocyst length 66-106 µm, width 67-97 µm.