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Oligosphaeridium pseudoabaculum
Oligosphaeridium pseudoabaculum Harding, 1990b, p.42, pl.24, figs.1–7 ex Harding in Williams et al. 1998, p.437.
Holotype: Harding, 1990b, pl.24, fig.1; Fauconnier and Masure, 2004, pl.60, fig.5. This name was not validly published in Harding (1990b) since the lodgement of the holotype was not specified (I.C.N. Article 40.7). Age: early Barremian.
Original diagnosis: Harding, 1990, p. 42
Shape: Main cyst body is spheroidal to prolate (may be accentuated by the development of axial compression folds). Greatest width in equatorial region. Epicyst and hypocyst-- dimensions. No dorso-ventral compression. Ambitus modified by tubiform processes about 2/3 main cyst body diameter in length. Processes developed on apical, pre- and post-cingular, X, Y and Z paraplates.
Phragma: Imperforate endophragm ca. 1µm thick has a pitted external surface (Plate 24, Fig. 6) Periphragm is ca. 1µm thick. Over the main cyst body the periphragm takes the form of a "spongy" textured layer, externally having a "porous" appearance caused by the partial fusion of the sporopollenin globules constituting this layer.
Around the process bases (often partially fenestrate) the sculpture develops into shallow striations. The periphragmal processes are externally laevigate, generally parallel sided and distally slightly flared. Process terminations are variable but not often strongly aculeate. The cyst is apiculocavate.
Paratabulation: Process formula: 0pr, 4", 6", 0c, 5""", 1p, 1"""", 1s. Inferred paratabulation is typically sexiform gonyaulacoid (see Evitt 1985: 56, 250-256, for discussion of other members of this genus).
Archaeopyle: Type (4A), 1u, A-C lost as a free, simple, polyplacoid operculum. Accessory archaeopyle sutures dedveloped between precingular paraplates.
Paracingulum: Devoid of processes, often shows up as a band of reduced periphragmal sculpture in the equatorial region of the main cyst body.
Parasulcus: Devoid of processes save for Z, ai can be distinguished along the archaeopyle suture.
Dimensions: Maximum diameter across processes = (142) 118.8 (85) µm. Main body diameter= (63) 55.4 (48) µm. Specimens = 19 (18).
Affinities:
Harding, 1990, p. 42: This species can be distinguished from other members of the genus by the combination of tubiform processes and the distinctive surface sculpture. The surface sculpture bears some resemblance to that of O. abaculum. The latter species, however, also possesses low ridges delineating a complete sexiform paratabulation. The endophragm of O. abaculum appears to be laevigate. Although the cingulum is sometimes discernible in O. pseudoabaculum, a complete paratabulation is never developed. This new species has only been isolated from the Hauptblatterton and its equivalents (i.e. restricted to late early Barremian time).
Holotype: Harding, 1990b, pl.24, fig.1; Fauconnier and Masure, 2004, pl.60, fig.5. This name was not validly published in Harding (1990b) since the lodgement of the holotype was not specified (I.C.N. Article 40.7). Age: early Barremian.
Original diagnosis: Harding, 1990, p. 42
Shape: Main cyst body is spheroidal to prolate (may be accentuated by the development of axial compression folds). Greatest width in equatorial region. Epicyst and hypocyst-- dimensions. No dorso-ventral compression. Ambitus modified by tubiform processes about 2/3 main cyst body diameter in length. Processes developed on apical, pre- and post-cingular, X, Y and Z paraplates.
Phragma: Imperforate endophragm ca. 1µm thick has a pitted external surface (Plate 24, Fig. 6) Periphragm is ca. 1µm thick. Over the main cyst body the periphragm takes the form of a "spongy" textured layer, externally having a "porous" appearance caused by the partial fusion of the sporopollenin globules constituting this layer.
Around the process bases (often partially fenestrate) the sculpture develops into shallow striations. The periphragmal processes are externally laevigate, generally parallel sided and distally slightly flared. Process terminations are variable but not often strongly aculeate. The cyst is apiculocavate.
Paratabulation: Process formula: 0pr, 4", 6", 0c, 5""", 1p, 1"""", 1s. Inferred paratabulation is typically sexiform gonyaulacoid (see Evitt 1985: 56, 250-256, for discussion of other members of this genus).
Archaeopyle: Type (4A), 1u, A-C lost as a free, simple, polyplacoid operculum. Accessory archaeopyle sutures dedveloped between precingular paraplates.
Paracingulum: Devoid of processes, often shows up as a band of reduced periphragmal sculpture in the equatorial region of the main cyst body.
Parasulcus: Devoid of processes save for Z, ai can be distinguished along the archaeopyle suture.
Dimensions: Maximum diameter across processes = (142) 118.8 (85) µm. Main body diameter= (63) 55.4 (48) µm. Specimens = 19 (18).
Affinities:
Harding, 1990, p. 42: This species can be distinguished from other members of the genus by the combination of tubiform processes and the distinctive surface sculpture. The surface sculpture bears some resemblance to that of O. abaculum. The latter species, however, also possesses low ridges delineating a complete sexiform paratabulation. The endophragm of O. abaculum appears to be laevigate. Although the cingulum is sometimes discernible in O. pseudoabaculum, a complete paratabulation is never developed. This new species has only been isolated from the Hauptblatterton and its equivalents (i.e. restricted to late early Barremian time).