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Charlesdowniea reticulata

Charlesdowniea reticulata, (Williams and Downie, 1966), Lentin and Vozzhennikova, 1989

Originally Wetzeliella, subsequently Kisselevia, thirdly Charlesdowniea, fourthly (and now) Sophismatia.

Holotype: Williams and Downie, 1966, pl.19, fig.3, text-fig.48
Locus typicus: London Clay, Sheppey, England
Stratum typicum: Early Eocene

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Original description as Wetzeliella (Wetzeliella) reticulata: [Williams and Downie, 1966, p. 187-188]:

Diagnosis:
Periphragm with distinctive pentagonal outline, produced into horns at each angle; one apical, two lateral and two antapical horns. Right antapical always larger than left antapical horn. Periphragm totally enclosing ovoidal capsule. Surface of periphragm bearing intratabular processes, usually restricted to simulate complexes; processes lying immediately within boundaries of plates.
Processes diversely united within each complex by series of trabeculae, giving a reticulum extending over plate and assuming plate outline. Processes of adjacent plates not unified.
Reflected tabulation 4', 3a, 7", 5c,
Archaeopyle present.

Description:
The shape and size of the plates of the periphragm of W. reticulata agree with those of W. coleothrypta (see previous description). The hollow, closed, cylindrical processes, in connection with the pericoel cavity are distally divided into numerous secae which ramify and are united by means of trabeculae with secae from processes of the same plate. The boundary of the reticulum thus formed is extremely regular, unconnected spines branching off only infrequently. Each reticulum mirrors the shape of the plate it overlies and is only slightly smaller. The trabeculae of the reticulum are taeniate. Processes can arise from any point on a plate within the simulate complex, sometimes even forming secondary rows, further strengthening the reticulum. The capsule is large, almost filling the pericoel apart from the horns. It has a thin slightly granular wall.

Dimensions:
Holotype: periphragm length 146 µm, breadth 162.5 µm, capsule length 106 µm, breadth 110 µm. Observed range: outer shell length 146-167 µm, breadth 150-162.5 µm. Capsule length 103-106 µm, breadth 95-110 µm.

Affinities:
W. reticulata has an outline closely approaching W. articulata which can occasionally have processes that are united distally, but never in the form of a reticulum reflecting each individual plate constituting the pericoel. W. reticulata differs from W. coleothrypta in the distal structure of the processes and in having two well developed antapical horns.

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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999

Charlesdowniea reticulata (Williams and Downie, 1966b) Lentin and Vozzhennikova, 1989, has processes which form simulate complexes. Distally, the processes are united by a series of trabeculae to form a regular reticulum, which reflects the outline of the plate.
Size: pericyst length 146-167 µm, width 150-162.5 µm, endocyst length 103-106 µm, width 95-110 µm
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