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Distatodinium craterum
Distatodinium craterum Eaton, 1976, p. 263-264
Taxonomic senior synonym: Distatodinium paradoxum, according to Fensome et al. (2009, p.31).
Contrary to the indication by Williams et al. (1998, p.200), Zevenboom and Santarelli in Zevenboom (1995) did not provide an emendation for this species.
The nomenclatural type of the genus Distatodinium remains the holotype of Distatodinium craterum.
Holotype: Eaton, 1976, pl.9, fig.1; Bujak et al., 1980, pl.2, figs.10–11; Fauconnier and Masure, 2004, pl.22, figs.4–6.
Locus typicus: Bracklesham Beds, Alum Bay, Isle of Wight, England
Stratum typicum: Late Eocene
Original description: Eaton, 1976, p. 263-264
Diagnosis: The cyst body has an elongate oval outline and a smooth or finely granular surface. The processes are typically broad, simple simple or branched, flattend and blade-like in cross-section, distally and proximally expanded. Distally they are bifurcate or trifurcate with complex secondary and tertiary branchlets, the ramifications having a twig-like appearance. Typically 13 to 17 processes on specimens which have lost the operculum; there are six processes on the precingular and five on the postcingular zone. Cingular zone devoid of processes. Usually one, sometimes two processes at the antapical pole. Between one and four additional processes may be present, apparently intermediate in position between the primary postcingular and antapical processes. The processes are also arranged into six rows parallel to the long axis of the cyst body. The straight or curved lines marking the divergence of the processes from the cyst body are also parallel to the long axis. Adjacent longitudinally aligned processes may be proximally united by membrane. Archaeopyle apical.
Dimensions: Holotype: cyst body (without operculum) 44 x 30 Ám ; processes, length up to 22 Ám, breadth up to 7 Ám. Observed range: cyst body (without operculum) 35 x 20 Ámto 55 x 38 Ám; processes, length up to 30 Ám, maximum breadth 5-11 Ám. (n = 25).
Remarks: No detached or in place opercula have been observed in D. craterum n. sp. The observed maximum number of processes is 17, but in the majority of specimens there are 14. The flattening and alignment of the processes parallel to the long axis of the cyst body, and the development of membrane proximally uniting longitudinally aligned processes in separate reflected tabulation zones, strangly suggest that the processes are sutural in position. This would indicate the presence of six precingular plates and at least five postcingular plates.
Affinities:
Eaton, 1976, p. 264
D. craterum is distinguished from all described species here attributed to Distatodinium by the overall broader and stronger form of its processes. It is further distinguished from D. ellipticum n. comb. by having considerably fewer processes which are longer, and distally more complex.
Taxonomic senior synonym: Distatodinium paradoxum, according to Fensome et al. (2009, p.31).
Contrary to the indication by Williams et al. (1998, p.200), Zevenboom and Santarelli in Zevenboom (1995) did not provide an emendation for this species.
The nomenclatural type of the genus Distatodinium remains the holotype of Distatodinium craterum.
Holotype: Eaton, 1976, pl.9, fig.1; Bujak et al., 1980, pl.2, figs.10–11; Fauconnier and Masure, 2004, pl.22, figs.4–6.
Locus typicus: Bracklesham Beds, Alum Bay, Isle of Wight, England
Stratum typicum: Late Eocene
Original description: Eaton, 1976, p. 263-264
Diagnosis: The cyst body has an elongate oval outline and a smooth or finely granular surface. The processes are typically broad, simple simple or branched, flattend and blade-like in cross-section, distally and proximally expanded. Distally they are bifurcate or trifurcate with complex secondary and tertiary branchlets, the ramifications having a twig-like appearance. Typically 13 to 17 processes on specimens which have lost the operculum; there are six processes on the precingular and five on the postcingular zone. Cingular zone devoid of processes. Usually one, sometimes two processes at the antapical pole. Between one and four additional processes may be present, apparently intermediate in position between the primary postcingular and antapical processes. The processes are also arranged into six rows parallel to the long axis of the cyst body. The straight or curved lines marking the divergence of the processes from the cyst body are also parallel to the long axis. Adjacent longitudinally aligned processes may be proximally united by membrane. Archaeopyle apical.
Dimensions: Holotype: cyst body (without operculum) 44 x 30 Ám ; processes, length up to 22 Ám, breadth up to 7 Ám. Observed range: cyst body (without operculum) 35 x 20 Ámto 55 x 38 Ám; processes, length up to 30 Ám, maximum breadth 5-11 Ám. (n = 25).
Remarks: No detached or in place opercula have been observed in D. craterum n. sp. The observed maximum number of processes is 17, but in the majority of specimens there are 14. The flattening and alignment of the processes parallel to the long axis of the cyst body, and the development of membrane proximally uniting longitudinally aligned processes in separate reflected tabulation zones, strangly suggest that the processes are sutural in position. This would indicate the presence of six precingular plates and at least five postcingular plates.
Affinities:
Eaton, 1976, p. 264
D. craterum is distinguished from all described species here attributed to Distatodinium by the overall broader and stronger form of its processes. It is further distinguished from D. ellipticum n. comb. by having considerably fewer processes which are longer, and distally more complex.