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Phthanoperidinium alectrolophum
Phthanoperidinium alectrolophum Eaton, 1976
Holotype: Eaton, 1976, pl.17, fig. 11; Bujak et al., 1980, pl.5, fig.9
Locus typicus: Bracklesham Beds, Alum Bay, Isle of Wight, England
Stratum typicum: ?Middle Eocene
Original diagnosis: Eaton, 1976, p. 295
Cyst body has a smooth surface, and a subcircular or rounded polygonal outline modified by a short blunt apical horn. Plate boundaries marked by thin smooth sutural crests of variable height. Undulating distal margin of crests frequently thickened, bearing numerous short solid spines. Cingular zone clearly defined, and slightly helicoid. Reflected tabulation 4", 3a, 7", 5""", 2""""; archaeopyle intercalary, formed by displacement of plate 2a.
Dimensions: Holotype: overall 59 x 48 µm; height of crests up to 7 µm; length of spines up to 2 µm. Observed range: overall 40 x 30 µm to 60 x 56 µm; height of crests up to 7 µm; length of spines up to 2 µm. (n = 6).
Affinities:
Eaton, 1976, p. 295: The sutural crests in Phthanoperidinium alectrolophum are similar in form to those of P. campoense Caro 1973 (incorrectly cited as Phtanoperidinium) and P. eocenicum (Cookson and Eisenack 1965). In P. campoense the crests are described as being surmounted by short irregularly distributed projections, as opposed to the relatively dense regular spine distribution in P. alectrolophum. The crests in P. eocenicum do not show a distal thickening, and their distal margin is described as being ornamented with evenly spaced granules and small tubercles, or sarsely denticulate. This species is further distinguished from P. alecrtolophum by the presence of a antapical horn.
Holotype: Eaton, 1976, pl.17, fig. 11; Bujak et al., 1980, pl.5, fig.9
Locus typicus: Bracklesham Beds, Alum Bay, Isle of Wight, England
Stratum typicum: ?Middle Eocene
Original diagnosis: Eaton, 1976, p. 295
Cyst body has a smooth surface, and a subcircular or rounded polygonal outline modified by a short blunt apical horn. Plate boundaries marked by thin smooth sutural crests of variable height. Undulating distal margin of crests frequently thickened, bearing numerous short solid spines. Cingular zone clearly defined, and slightly helicoid. Reflected tabulation 4", 3a, 7", 5""", 2""""; archaeopyle intercalary, formed by displacement of plate 2a.
Dimensions: Holotype: overall 59 x 48 µm; height of crests up to 7 µm; length of spines up to 2 µm. Observed range: overall 40 x 30 µm to 60 x 56 µm; height of crests up to 7 µm; length of spines up to 2 µm. (n = 6).
Affinities:
Eaton, 1976, p. 295: The sutural crests in Phthanoperidinium alectrolophum are similar in form to those of P. campoense Caro 1973 (incorrectly cited as Phtanoperidinium) and P. eocenicum (Cookson and Eisenack 1965). In P. campoense the crests are described as being surmounted by short irregularly distributed projections, as opposed to the relatively dense regular spine distribution in P. alectrolophum. The crests in P. eocenicum do not show a distal thickening, and their distal margin is described as being ornamented with evenly spaced granules and small tubercles, or sarsely denticulate. This species is further distinguished from P. alecrtolophum by the presence of a antapical horn.