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Phthanoperidinium diamantum
Phtanoperidinium? diamantum (Churchill and Sarjeant, 1962) Lentin and Williams, 1973
Now Gonyaulacysta. Originally Peridinium, subsequently Phthanoperidinium?, thirdly (and now) Gonyaulacysta. At the time of the transfer, Lentin and Williams, 1973 questionably included this species in Phthanoperidinium.
Holotype: Churchill and Sarjeant, 1962, pl.1, fig.19; text-fig. 3
Locus typicus: West Muir, Australia
Stratum typicum: Atlantic Stage, 2500-5000 B.C.
Original diagnosis: Churchill and Sarjeant, 1962, p.34: Peridinium? diamantum
A species of fossil dinoflagellate having a biconical theca, prolonged into rounded prominences at apex and antapex. Transverse furrow broad, laevo-rotatory; longitudinal furrow also broad, subdivided into four distinct sections (? plates). Tabulation 3", ?6", 4 l.f., 8""", 1"""": no intercalary plates apparently present. Plate 1""" narrow, plate 4""" very reduced. Plate boundaries and the borders of the furrows bear very short, knobbed spinelets.
Original description: Churchill and Sarjeant, 1962, p.34, 36: Peridinium? diamantum
Shell yellowish, minutely granular: tabulation poorly marked and determinable only with difficulty. In many specimens the epitheca is damaged, evidently as a result of pylome formation; the number of apical and pre-equatorial plates was, as a result, not determined with certainty. Plate 1" forms the anterior prolongation of the longitudinal furrow. Two other apical plates, tentatively numbered 2" and 3", are recognisable on the dorsal surface: the full number of apical plates is probably 4 or 5. At least six pre-equatorial plates were certainly distinguished; the full number may be 7 or 8. The transverse furrow is slightly hollowed; its two ends differ in anteroposterior position by the furrow"s width. It is divided into sections by low ridges not bearing spines. The longitudinal furrow extends across about hvothirds of the ventral surface: it is separated from the apex by plate 1" and from the antapex by an elongate antapical plate, entirely ventral in situation. The longitudinal furrow is subdivided by pronounced ridges into four distinct sections, or plates, here designated 1-4 l.f. Plates 1-3 l.f. are each subquadrate, plate 4 l.f. elongate. Eight post-equatorial plates are present: plate 1""" is narrow and elongate, plate 4""" reduced and almost triangular. Plates 3""", 5""" and 6""", all dorsal in position, taper to a junction at the antapex.
Dimensions. Holotype; length 93 µm, breadth 63 µm. Observed range: lengths 75-105 µm (12 specimens).
Affinities:
Churchill and Sarjeant, 1962, p.36: Peridinium? diamantum
?Peridinium diamantum is characterised by shape, the tabulation of ventral surface and hypotheca, and the crest ornament. The generic attribution of the species is very questionable. In general form, it resembles genera of the Family Peridiniaceae, in particular Peridinium itself, Murrayella and Goniodinium: however, the higher number of hypothecal plates (the tabulation of Peridinium is 4", 2-3a, 7", 5""", 2""""; of Murrayella, 2-4", 2a, 6", 5""", 1""""; and of Goniodinium, 4", 6", 5-6""", 2p, 3"""") and differences in overall character separate it from all described genera. In view of the doubt as to the epithecal tabulation of ? P. diamantum, it was considered, however, inappropriate to erect a new genus.
Now Gonyaulacysta. Originally Peridinium, subsequently Phthanoperidinium?, thirdly (and now) Gonyaulacysta. At the time of the transfer, Lentin and Williams, 1973 questionably included this species in Phthanoperidinium.
Holotype: Churchill and Sarjeant, 1962, pl.1, fig.19; text-fig. 3
Locus typicus: West Muir, Australia
Stratum typicum: Atlantic Stage, 2500-5000 B.C.
Original diagnosis: Churchill and Sarjeant, 1962, p.34: Peridinium? diamantum
A species of fossil dinoflagellate having a biconical theca, prolonged into rounded prominences at apex and antapex. Transverse furrow broad, laevo-rotatory; longitudinal furrow also broad, subdivided into four distinct sections (? plates). Tabulation 3", ?6", 4 l.f., 8""", 1"""": no intercalary plates apparently present. Plate 1""" narrow, plate 4""" very reduced. Plate boundaries and the borders of the furrows bear very short, knobbed spinelets.
Original description: Churchill and Sarjeant, 1962, p.34, 36: Peridinium? diamantum
Shell yellowish, minutely granular: tabulation poorly marked and determinable only with difficulty. In many specimens the epitheca is damaged, evidently as a result of pylome formation; the number of apical and pre-equatorial plates was, as a result, not determined with certainty. Plate 1" forms the anterior prolongation of the longitudinal furrow. Two other apical plates, tentatively numbered 2" and 3", are recognisable on the dorsal surface: the full number of apical plates is probably 4 or 5. At least six pre-equatorial plates were certainly distinguished; the full number may be 7 or 8. The transverse furrow is slightly hollowed; its two ends differ in anteroposterior position by the furrow"s width. It is divided into sections by low ridges not bearing spines. The longitudinal furrow extends across about hvothirds of the ventral surface: it is separated from the apex by plate 1" and from the antapex by an elongate antapical plate, entirely ventral in situation. The longitudinal furrow is subdivided by pronounced ridges into four distinct sections, or plates, here designated 1-4 l.f. Plates 1-3 l.f. are each subquadrate, plate 4 l.f. elongate. Eight post-equatorial plates are present: plate 1""" is narrow and elongate, plate 4""" reduced and almost triangular. Plates 3""", 5""" and 6""", all dorsal in position, taper to a junction at the antapex.
Dimensions. Holotype; length 93 µm, breadth 63 µm. Observed range: lengths 75-105 µm (12 specimens).
Affinities:
Churchill and Sarjeant, 1962, p.36: Peridinium? diamantum
?Peridinium diamantum is characterised by shape, the tabulation of ventral surface and hypotheca, and the crest ornament. The generic attribution of the species is very questionable. In general form, it resembles genera of the Family Peridiniaceae, in particular Peridinium itself, Murrayella and Goniodinium: however, the higher number of hypothecal plates (the tabulation of Peridinium is 4", 2-3a, 7", 5""", 2""""; of Murrayella, 2-4", 2a, 6", 5""", 1""""; and of Goniodinium, 4", 6", 5-6""", 2p, 3"""") and differences in overall character separate it from all described genera. In view of the doubt as to the epithecal tabulation of ? P. diamantum, it was considered, however, inappropriate to erect a new genus.