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Wetzeliella varielongituda
Wetzeliella varielongituda Williams and Downie, 1966
Now Dracodinium. Originally Wetzeliella, subsequently (and now) Dracodinium.
Holotype: Williams and Downie, 1966, pl.20, fig.4
Locus typicus: London Clay, Sheppey, England
Stratum typicum: Early Eocene
Translation Gocht, 1969: Geological Survey of Canada
Original diagnosis: Williams and Downie, 1966, p. 196-197
Periphragm outline sub-rhomboidal, with short broad lateral horns, a short wide apical horn and one well developed (right) antapical horn. Left antapical horn represented by slight protuberance on left antapical margin. Capsule thick walled, often coarsely granular. Processes extremely short on ambitus of periphragm and increasing in length further away from ambitus. Distally processes bifid, aculeate, acuminate or evexate.
Dimensions: holotype: outer shell, length 103 µm, breadth 100 µm. Capsule, length 73 µm, breadth 71 µm, Observed range: outer shell, length 96-126 µm, breadth 90-125 µm. Capsule, length 64-79 µm, breadth 63-84 µm. Length / breadth ratio of pericoel 1-1 to 1.1-1.
Original description: Williams and Davey, 1966, p. 197
One of the diagnostic features of W. varielongituda are the processes. The wall of the periphragm is up to 1/2 Ám in thickness, so that the slender processes have only a minute central tubule, along their length. They are distally closed, proximally open to the pericoel. The processes can be granular and are always simple. The shortest processes occur on the ambitus of the pericoel and particularly is this so on the lateral horns and epitract. It is these processes that can be acuminate or evexate distally. The processes are regularly orientated in simulate complexes or are irregular occurring within the complexes. Typical Wetzeliella tabulation is decipherable, with the archeopyle intercalary.
The horns of W. varielongituda tend to be broad and low, merging imperceptibly with the lateral margins of the periphragm. This is especially so with the apical horn. The capsule is sub-circular in outline, ellipsoidal in cross section and has a wall up to 3.5 µm thick. The wall often shows local thickening directly opposite the horns. Distance of the capsule from the inner surface of the periphragm is variable.
Affinities:
Williams and Downie, 1966, p. 197: The nature of the processes, outline of the pericoel and structure of the capsule readily distinguish Wetzeliella (W.) varielongituda from other species of Wetzeliella.
Description Gocht, 1969, p.21:
The body is pentangular and convex. The horns are well developed, broad-based, and frequently fused, and show membrane perforations. The smooth outer armor has straight or only slightly notched lateral margins and bears numerous, thin processes. The inner body is strong and scabrate.
The variation of the body shape results from whether the polar horns, especially the apical horn, are acute- or obtuse- angled, and from the shape of the line between the horns, which determines the distance from the inner body. Generally, the process bases do not affect the shape. The processes are slender, flexible, and sometimes especially long on the horns. They have fine spinules at the end. In exceptional cases, the shaft may also be furcate, and in one such instance, the shaft showed several perforations. The processes may be grouped locally into rows, especially on the mid-dorsal area or along the archeopyle boundaries.
Not infrequently, the horns have membrane perforations, as described under W. draco. There may also be a piece of membrane recessed between the antapical horns. The wall of the inner body varies in thickness, but is almost always thicker than the outer membrane. The capsular surface is scabrate.
The archeopyle of the outer membrane does not appear to coincide with that of the capsule; but in the present case, this can be easily explained by the diverging planes of the pylome of the outer armor and that of the (more convex) capsule. As well, there seems to be an actual size difference (the outer pylome is larger). In the cingular region, the boundaries are closely congruent with the exception of a narrow strip, which, however, is regularly present; toward the apex, the outer pylome usually extends beyond the capsular margin. In some cases, flagellar insertions were observed. Variants of W. varielongituda are transitional towards W. (Rhomb.) glabra Cookson (see Morgenroth, 1966). Apart from the processes, W. varielongituda is closer to species of subgen. Rhombodinium than to Wetzeliella species.
Occurrence: Early Eocene.
Now Dracodinium. Originally Wetzeliella, subsequently (and now) Dracodinium.
Holotype: Williams and Downie, 1966, pl.20, fig.4
Locus typicus: London Clay, Sheppey, England
Stratum typicum: Early Eocene
Translation Gocht, 1969: Geological Survey of Canada
Original diagnosis: Williams and Downie, 1966, p. 196-197
Periphragm outline sub-rhomboidal, with short broad lateral horns, a short wide apical horn and one well developed (right) antapical horn. Left antapical horn represented by slight protuberance on left antapical margin. Capsule thick walled, often coarsely granular. Processes extremely short on ambitus of periphragm and increasing in length further away from ambitus. Distally processes bifid, aculeate, acuminate or evexate.
Dimensions: holotype: outer shell, length 103 µm, breadth 100 µm. Capsule, length 73 µm, breadth 71 µm, Observed range: outer shell, length 96-126 µm, breadth 90-125 µm. Capsule, length 64-79 µm, breadth 63-84 µm. Length / breadth ratio of pericoel 1-1 to 1.1-1.
Original description: Williams and Davey, 1966, p. 197
One of the diagnostic features of W. varielongituda are the processes. The wall of the periphragm is up to 1/2 Ám in thickness, so that the slender processes have only a minute central tubule, along their length. They are distally closed, proximally open to the pericoel. The processes can be granular and are always simple. The shortest processes occur on the ambitus of the pericoel and particularly is this so on the lateral horns and epitract. It is these processes that can be acuminate or evexate distally. The processes are regularly orientated in simulate complexes or are irregular occurring within the complexes. Typical Wetzeliella tabulation is decipherable, with the archeopyle intercalary.
The horns of W. varielongituda tend to be broad and low, merging imperceptibly with the lateral margins of the periphragm. This is especially so with the apical horn. The capsule is sub-circular in outline, ellipsoidal in cross section and has a wall up to 3.5 µm thick. The wall often shows local thickening directly opposite the horns. Distance of the capsule from the inner surface of the periphragm is variable.
Affinities:
Williams and Downie, 1966, p. 197: The nature of the processes, outline of the pericoel and structure of the capsule readily distinguish Wetzeliella (W.) varielongituda from other species of Wetzeliella.
Description Gocht, 1969, p.21:
The body is pentangular and convex. The horns are well developed, broad-based, and frequently fused, and show membrane perforations. The smooth outer armor has straight or only slightly notched lateral margins and bears numerous, thin processes. The inner body is strong and scabrate.
The variation of the body shape results from whether the polar horns, especially the apical horn, are acute- or obtuse- angled, and from the shape of the line between the horns, which determines the distance from the inner body. Generally, the process bases do not affect the shape. The processes are slender, flexible, and sometimes especially long on the horns. They have fine spinules at the end. In exceptional cases, the shaft may also be furcate, and in one such instance, the shaft showed several perforations. The processes may be grouped locally into rows, especially on the mid-dorsal area or along the archeopyle boundaries.
Not infrequently, the horns have membrane perforations, as described under W. draco. There may also be a piece of membrane recessed between the antapical horns. The wall of the inner body varies in thickness, but is almost always thicker than the outer membrane. The capsular surface is scabrate.
The archeopyle of the outer membrane does not appear to coincide with that of the capsule; but in the present case, this can be easily explained by the diverging planes of the pylome of the outer armor and that of the (more convex) capsule. As well, there seems to be an actual size difference (the outer pylome is larger). In the cingular region, the boundaries are closely congruent with the exception of a narrow strip, which, however, is regularly present; toward the apex, the outer pylome usually extends beyond the capsular margin. In some cases, flagellar insertions were observed. Variants of W. varielongituda are transitional towards W. (Rhomb.) glabra Cookson (see Morgenroth, 1966). Apart from the processes, W. varielongituda is closer to species of subgen. Rhombodinium than to Wetzeliella species.
Occurrence: Early Eocene.