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Oligosphaeridium distinctum
From Fensome et al., 2019:
Oligosphaeridium distinctum Duxbury, 2018, p.188, pl.7, figs.1,3–5,8. Holotype: Duxbury, 2018, pl.1, figs.1,4,8. Age: early
Valanginian.
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Original description Duxbury, 2018:
Plate 7, figures 1, 3, 4, 5, 8
Holotype: Plate 7, Figures 1, 4, 8.
Type Locality: Well 20/01-10Z at 9053.00 ft (conventional core chip), lower Valanginian. Holotype: E. F. E35.0.
Derivation of Name: From the Latin distinctus, separate, different – in reference to the distinctive nature of this species.
Diagnosis: A large, robust, fairly thick-walled species with a spheroidal, microgranular main body. A narrow cingulum is sometimes faintly outlined by low surface ridges. Hollow, mesotabular processes indicate a tabulation scheme of 4', 6'', 0c, 6'', 1p, 1''''. Processes taper, being narrowest at about half their length. Distal terminations vary from simple, entire margins with short fringing spines to broader terminations which are distally palmate with lateral perforations. The archeopyle involves the loss of four apical plates and significant splitting along precingular sutures often occurs, resulting in a very broad archeopyle margin.
Dimensions: Holotype – Central body – 63 × 76 μm. Overall: 122 × 114μm
Other measured specimens:
Central body (operculum detached) – 73 (63) 51 μm × 76 (66) 51 μm.
Overall (operculum detached) – 129 (113) 89 μm × 152 (119) 101 μm.
Specimens Measured: 20.
Remarks: This distinctive species shares relatively simple distal process terminations with Oligosphaeridium totum Brideaux 1971 and is possibly the species referred to as O. totum in Davies (1983, p. 10), occurring within and above his Oppel-Zone O (early to possibly late Valanginian), although Davies did not illustrate this taxon. Oligosphaeridium distinctum n. sp. differs from O. totum, however, in being much larger (the main body width alone is c. 70% larger than that of O. totum), in being more robust and in possessing a microgranular body ornament. It typically shows markedly less distal process flaring than O. totum, with processes often similar to those of some species of Kleithriasphaeridium Davey 1974. Palmate process terminations are also common, however, and some specimens display significantly shorter epicystal processes than those on the hypocyst. A faint cingulum can be outlined by very low ridges, although this feature is uncommon. No evidence of tabulation was observed other than for the process distribution, archeopyle margin and cingular ridges.
Oligosphaeridium distinctum Duxbury, 2018, p.188, pl.7, figs.1,3–5,8. Holotype: Duxbury, 2018, pl.1, figs.1,4,8. Age: early
Valanginian.
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Original description Duxbury, 2018:
Plate 7, figures 1, 3, 4, 5, 8
Holotype: Plate 7, Figures 1, 4, 8.
Type Locality: Well 20/01-10Z at 9053.00 ft (conventional core chip), lower Valanginian. Holotype: E. F. E35.0.
Derivation of Name: From the Latin distinctus, separate, different – in reference to the distinctive nature of this species.
Diagnosis: A large, robust, fairly thick-walled species with a spheroidal, microgranular main body. A narrow cingulum is sometimes faintly outlined by low surface ridges. Hollow, mesotabular processes indicate a tabulation scheme of 4', 6'', 0c, 6'', 1p, 1''''. Processes taper, being narrowest at about half their length. Distal terminations vary from simple, entire margins with short fringing spines to broader terminations which are distally palmate with lateral perforations. The archeopyle involves the loss of four apical plates and significant splitting along precingular sutures often occurs, resulting in a very broad archeopyle margin.
Dimensions: Holotype – Central body – 63 × 76 μm. Overall: 122 × 114μm
Other measured specimens:
Central body (operculum detached) – 73 (63) 51 μm × 76 (66) 51 μm.
Overall (operculum detached) – 129 (113) 89 μm × 152 (119) 101 μm.
Specimens Measured: 20.
Remarks: This distinctive species shares relatively simple distal process terminations with Oligosphaeridium totum Brideaux 1971 and is possibly the species referred to as O. totum in Davies (1983, p. 10), occurring within and above his Oppel-Zone O (early to possibly late Valanginian), although Davies did not illustrate this taxon. Oligosphaeridium distinctum n. sp. differs from O. totum, however, in being much larger (the main body width alone is c. 70% larger than that of O. totum), in being more robust and in possessing a microgranular body ornament. It typically shows markedly less distal process flaring than O. totum, with processes often similar to those of some species of Kleithriasphaeridium Davey 1974. Palmate process terminations are also common, however, and some specimens display significantly shorter epicystal processes than those on the hypocyst. A faint cingulum can be outlined by very low ridges, although this feature is uncommon. No evidence of tabulation was observed other than for the process distribution, archeopyle margin and cingular ridges.