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Pentadinium omasum
Pentadinium omasum Harding, 1990
Name not validly published since lodgment of holotype not specified (I.C.B.N. Article 37.5).
Holotype: Harding, 1990, pl.17, fig.1,3
Locus typicus: O. Gott, Lower Saxony, Germany
Stratum typicum: Late Barremian
Original diagnosis: Harding, 1990, p.36-37
Shape: Ambitus subpentagonal to ovoid. Small apical prominence. Outline modified by camocavate nature of the equatorial region (the periparacingulum is separated from the endocyst in all but the parasulcal region). Greatest width across paracingulum. Epicyst and hypocyst of equal dimensions. No dorso-ventral compression.
Wall: Periphragm ca. 0.75 µm thick, weakly granular sculpture. Endophragm up to 1 µm thick, of spheroidal shape with a pseudopunctate/"orange-peel" type surface sculpture. Camocavate: entire dorsal part of the paracingulum is separated from the endocyst by up to 15 µm. Suturocavation developed to varying degrees along the parasutures adjacent to the paracingulum.
Paratabulation: indicated by undulate septa of variable height (low in parasulcal region - ca. 2 µm, up to 5 µm in antapical region); S-type sexiform gonyaulacoid paratabulation as shown by the parasutural septa: 4", 6", 6c, 6""", 1"""", 1p, 5s. A and lu very small, with the parasuture dividing them often suppressed. Suppression of the parasulcal sutures also occurs. A porichnion is rarely observed, when present lies on A/lu.
Archaeopyle: Type -/P4 - fourth precingular paraplate is lost from the endocyst in archaeopyle formation as a free, monoplacoid operculum. It appears that there was no fourth precingular periphragmal paraplate formed on encystment.
Paracingulum: Displayed as a pronounced outbulging of the periphragm. Laevorotatory, displaced by 1/2-2 cingulum widths.
Parasulcus: S-type, parasutures often suppressed.
Dimensions: Length (56) 48.1 (44) µm. Width (55) 47.4 (42) µm. Specimens = 14 (13).
Affinities:
Harding, 1990, p. 37: This new species is restricted to rocks of late Barremian age. It differs from Stephodinium in that the separation of periphragm and endophragm is merely paracingular and not dorsal (Stover and Evitt 1978). It differs from Pentadinium polypodum Edwards 1982, to which it appears superficially similar (Edwards 1982: Plate 3, Fig. 5), as it lacks gonal processes.
Name not validly published since lodgment of holotype not specified (I.C.B.N. Article 37.5).
Holotype: Harding, 1990, pl.17, fig.1,3
Locus typicus: O. Gott, Lower Saxony, Germany
Stratum typicum: Late Barremian
Original diagnosis: Harding, 1990, p.36-37
Shape: Ambitus subpentagonal to ovoid. Small apical prominence. Outline modified by camocavate nature of the equatorial region (the periparacingulum is separated from the endocyst in all but the parasulcal region). Greatest width across paracingulum. Epicyst and hypocyst of equal dimensions. No dorso-ventral compression.
Wall: Periphragm ca. 0.75 µm thick, weakly granular sculpture. Endophragm up to 1 µm thick, of spheroidal shape with a pseudopunctate/"orange-peel" type surface sculpture. Camocavate: entire dorsal part of the paracingulum is separated from the endocyst by up to 15 µm. Suturocavation developed to varying degrees along the parasutures adjacent to the paracingulum.
Paratabulation: indicated by undulate septa of variable height (low in parasulcal region - ca. 2 µm, up to 5 µm in antapical region); S-type sexiform gonyaulacoid paratabulation as shown by the parasutural septa: 4", 6", 6c, 6""", 1"""", 1p, 5s. A and lu very small, with the parasuture dividing them often suppressed. Suppression of the parasulcal sutures also occurs. A porichnion is rarely observed, when present lies on A/lu.
Archaeopyle: Type -/P4 - fourth precingular paraplate is lost from the endocyst in archaeopyle formation as a free, monoplacoid operculum. It appears that there was no fourth precingular periphragmal paraplate formed on encystment.
Paracingulum: Displayed as a pronounced outbulging of the periphragm. Laevorotatory, displaced by 1/2-2 cingulum widths.
Parasulcus: S-type, parasutures often suppressed.
Dimensions: Length (56) 48.1 (44) µm. Width (55) 47.4 (42) µm. Specimens = 14 (13).
Affinities:
Harding, 1990, p. 37: This new species is restricted to rocks of late Barremian age. It differs from Stephodinium in that the separation of periphragm and endophragm is merely paracingular and not dorsal (Stover and Evitt 1978). It differs from Pentadinium polypodum Edwards 1982, to which it appears superficially similar (Edwards 1982: Plate 3, Fig. 5), as it lacks gonal processes.