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Wilsonidium tesselatum
From Fensome et al., 2019:
Wilsonidium tesselatum (Chateauneuf and Gruas-Cavagnetto, 1978) Islam, 1983
Originally Apectodinium homomorphum subsp. tesselatum, subsequently Wilsonidium tesselatum, thirdly (and now) Axiodinium tesselatum. This taxon was raised to the species level by Islam, 1983.
Holotype: Chateauneuf and Gruas-Cavagnetto, 1978, pl.1, figs.1-2
Age: Early Eocene (Sparnacian)
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Original description, Chateauneuf and Gruas-Cavagnetto, 1978 (translated by MPP 2024)
Derivation of subspecies name: checkered surface, squares: plates, indicates the tabulation of this subspecies.
Diaganose: subspecies of Apectodinium possessing the characteristics of the species homomorphum from the point of view of general shape, archeopyle, outline and nature of processes. This species, however, clearly differs from the classic A. homomorphum type by its clearly more pentagonal shape, the development of the lateral and anatapical horns as well as by the presence of a tabulation. On the other hand, the endocoel is detached from the pericoel at the level of the epitract and the cingulum.
Locality: Cuise-la-Motte survey (96.60 m): Lower Sparnacian; Paris Basin (France)
Dimensions:
Holotype: 70/80 µm (length/width);
Endoblast: length 55 µm, width 60 µm;
Apical horns 5µm;
lateral horns 15 µm;
Antapical horn 5µm;
Process length 10 µm
Description: Cyst with rounded pentagonal shape: epitract of rounded triangular shape, angular subpolygonal hypotract. Reduced apical horn, materialized by the developed this level, wider than long, most often with dichotomized ends. Anatapical horns of variable length and development, the right antapical being most often larger in size than the left. These horns are formed by the expansions of the pericoel at this level. Endophragm detached from the periphragm (pericoel with a thickness varying from 1 to 3 µm).
Clear tabulation of the type: Peritabular processes united at the base in a continuous membrane very clearly reflecting the contour of each plate: distal end simple pointed or bifurcated, rarely branched. Archeopyle characterizes the genus Apectodinium, subquadrangular, with periphragm and endophargm in close contact.
Remarks: The subspecies defined here resembles Apectodinium angustum (Harland) in general outline. It differs from it by the form of the processes and its clearly defined tabulation. However, there are all the transitions with classic A. homomorphum which are found in large numbers in the same levels. It is clearly differentiated from the species of the group parvum, paniculatum and hyperacanthum by its clear endocoele and by the shape and arrangement of the peritabuary processes.
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Description: Islam 1983, p. 90-91
Cyst dorsoventrally compressed peridinioid with one apical, two paracingular and two antapical horns; proximochorate and cornucavate; possesses numerous short thinly tubular parasutural processes, proximally closed wider and joined by parasutural septa, distally wide, bifurcate or aculeate and open or closed, and define the paratabulation as 4", 3a, 7" ?6c, 5"", 2""; archeopyle intercalary type I/I representing paraplate 2a, operculum free.
Occurrence. Shapley Heath: C1760; Bracklesham Bay: BB29.
Remarks: Islam 1983, p. 90-91
The taxon is generically reattributed due to its possession of parasutural processes which also required specific upgrading. Apart from two species questionably referred to this genus (Lentin and Williams, 1981), Wilsonidium was unrepresented in the Northern Hemisphere. This species may also provide a clue to the missing link in the evolution of the genus as considered by Costa and Downie (1980).
Wilsonidium tesselatum (Chateauneuf and Gruas-Cavagnetto, 1978) Islam, 1983
Originally Apectodinium homomorphum subsp. tesselatum, subsequently Wilsonidium tesselatum, thirdly (and now) Axiodinium tesselatum. This taxon was raised to the species level by Islam, 1983.
Holotype: Chateauneuf and Gruas-Cavagnetto, 1978, pl.1, figs.1-2
Age: Early Eocene (Sparnacian)
----------------------------------------------------------------------------------------------------------------------------------
Original description, Chateauneuf and Gruas-Cavagnetto, 1978 (translated by MPP 2024)
Derivation of subspecies name: checkered surface, squares: plates, indicates the tabulation of this subspecies.
Diaganose: subspecies of Apectodinium possessing the characteristics of the species homomorphum from the point of view of general shape, archeopyle, outline and nature of processes. This species, however, clearly differs from the classic A. homomorphum type by its clearly more pentagonal shape, the development of the lateral and anatapical horns as well as by the presence of a tabulation. On the other hand, the endocoel is detached from the pericoel at the level of the epitract and the cingulum.
Locality: Cuise-la-Motte survey (96.60 m): Lower Sparnacian; Paris Basin (France)
Dimensions:
Holotype: 70/80 µm (length/width);
Endoblast: length 55 µm, width 60 µm;
Apical horns 5µm;
lateral horns 15 µm;
Antapical horn 5µm;
Process length 10 µm
Description: Cyst with rounded pentagonal shape: epitract of rounded triangular shape, angular subpolygonal hypotract. Reduced apical horn, materialized by the developed this level, wider than long, most often with dichotomized ends. Anatapical horns of variable length and development, the right antapical being most often larger in size than the left. These horns are formed by the expansions of the pericoel at this level. Endophragm detached from the periphragm (pericoel with a thickness varying from 1 to 3 µm).
Clear tabulation of the type: Peritabular processes united at the base in a continuous membrane very clearly reflecting the contour of each plate: distal end simple pointed or bifurcated, rarely branched. Archeopyle characterizes the genus Apectodinium, subquadrangular, with periphragm and endophargm in close contact.
Remarks: The subspecies defined here resembles Apectodinium angustum (Harland) in general outline. It differs from it by the form of the processes and its clearly defined tabulation. However, there are all the transitions with classic A. homomorphum which are found in large numbers in the same levels. It is clearly differentiated from the species of the group parvum, paniculatum and hyperacanthum by its clear endocoele and by the shape and arrangement of the peritabuary processes.
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Description: Islam 1983, p. 90-91
Cyst dorsoventrally compressed peridinioid with one apical, two paracingular and two antapical horns; proximochorate and cornucavate; possesses numerous short thinly tubular parasutural processes, proximally closed wider and joined by parasutural septa, distally wide, bifurcate or aculeate and open or closed, and define the paratabulation as 4", 3a, 7" ?6c, 5"", 2""; archeopyle intercalary type I/I representing paraplate 2a, operculum free.
Occurrence. Shapley Heath: C1760; Bracklesham Bay: BB29.
Remarks: Islam 1983, p. 90-91
The taxon is generically reattributed due to its possession of parasutural processes which also required specific upgrading. Apart from two species questionably referred to this genus (Lentin and Williams, 1981), Wilsonidium was unrepresented in the Northern Hemisphere. This species may also provide a clue to the missing link in the evolution of the genus as considered by Costa and Downie (1980).