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Selenopemphix quanta
Selenopemphix quanta (Bradford, 1975, p.3067,3069, figs.5–7) Matsuoka, 1985a, p.51.
Originally Multispinula, subsequently (and now) Selenopemphix. This species was retained in Selenopemphix by Head (1993, p.36).
Motile equivalent: Protoperidinium conicum (Gran, 1900) Balech, 1974, according to Harland (1981, p.68) — however, see Head (1993, p.37).
Holotype: Bradford, 1975, fig.5; Fensome et al., 1995, fig.1 — p.1725.
Age: Holocene.
Original description: Bradford, 1975, p. 3067-3070
Diagnosis: Proximate cyst with a wide variation in ambital and polar dimensions. Usually circular to reniform in polar view, often with a strong compression. Considerable variation exists in overall size. No antapical horns. A small apical projection may be present, often surrounded by spines. Phragma ornamented with apparently solid, pointed spines. Two rows of strongly developed spines outline the cingular zone. Archeopyle intercalary; wall thin.
Dimensions: Holotype: lateral breadth 56 µm, dorsoventral breadth 50 µm, length of processes 10 µm, overall lateral breadth 24-67 µm, dorsoventral breadth 24-52 µm, length of processes 6-15 µm, overall lateral breadth 35-90 µm, overall dorsoventral breadth 35-74 µm. Number of specimens measured 17. No specimens were found orientated in suitable position for the length of the test to be measured. (Refer to Wall and Dale 1968 for other dimensions.)
Description (annotated): Forms incorporated into this species exhibit a wide variation in size and shape. The ambitus is either ovoidal, circular, or rhomboidal, while in polar view the cysts are circular to reniform in outline. Strong polar compression is observed in most specimens. The smaller forms are usually more rhomboidal in ambitus and circular in polar view. The epitract and hypotract are of a similar size; their flanks are straight to convex. No antapical horns are present; however, a small apical projection can usually be recognized. The phragma is ornamented with straight or curved, distally pointed spines; these may be solid and are usually circular at their bases. The number of spines present on each cyst is extremely variable; however, the smaller the forms are the longer and less abundant the spines appear to be. One row of spines delineates the apical region of the test. The cingular zone is wide, circular, and outlined by more strongly developed spines. The sulcus is usually observed in polar view and it helps to give the sometimes characteristic reniform shape to the cyst. It is fairly narrow and moderately deep. The archeopyle reflects 2a (intercalary) plate; it is relatively small, laterally elongate, and six sided. The wall is thin, often colourless, single layered , and with a smooth to psilate ornamentation.
Remarks (annotated): A continuous morphologic gradation between the large, reniform-shaped to the smaller circular forms seems apparent. Generally, the longer the spines and the less abundant they are, the smaller the cysts tend to be.
Thecal affinity: The larger cyst forms have been shown by incubation experiments (Wall and Dale, 1968) to give rise to Peridinium conicum. The smaller cyst forms produce (Wall and Dale, 1968) thecal characteristics of Peridinium nudum.
Supplemental description: Reid, 1977, p.448
The cysts have polar compression giving a rhomboidal shape in equatorial view. The wall is thin, single layered, with a smooth surface which is ornamented by rows of solid curved spines. Two rows form a V shaped outline at the base of the ventral sulcus which expands in a posterior direction from the girdle. Processes are not present in the sulcus itself and in the anterior ventral areas. The girdle is circular. Two small scars in the ventral sulcus reflect the position of the flagellar pores. A laterally elongated six-sided archeopyle is found with rounded angles. The colour of specimens varies from colourless, to grey brown, to dark brown.
Originally Multispinula, subsequently (and now) Selenopemphix. This species was retained in Selenopemphix by Head (1993, p.36).
Motile equivalent: Protoperidinium conicum (Gran, 1900) Balech, 1974, according to Harland (1981, p.68) — however, see Head (1993, p.37).
Holotype: Bradford, 1975, fig.5; Fensome et al., 1995, fig.1 — p.1725.
Age: Holocene.
Original description: Bradford, 1975, p. 3067-3070
Diagnosis: Proximate cyst with a wide variation in ambital and polar dimensions. Usually circular to reniform in polar view, often with a strong compression. Considerable variation exists in overall size. No antapical horns. A small apical projection may be present, often surrounded by spines. Phragma ornamented with apparently solid, pointed spines. Two rows of strongly developed spines outline the cingular zone. Archeopyle intercalary; wall thin.
Dimensions: Holotype: lateral breadth 56 µm, dorsoventral breadth 50 µm, length of processes 10 µm, overall lateral breadth 24-67 µm, dorsoventral breadth 24-52 µm, length of processes 6-15 µm, overall lateral breadth 35-90 µm, overall dorsoventral breadth 35-74 µm. Number of specimens measured 17. No specimens were found orientated in suitable position for the length of the test to be measured. (Refer to Wall and Dale 1968 for other dimensions.)
Description (annotated): Forms incorporated into this species exhibit a wide variation in size and shape. The ambitus is either ovoidal, circular, or rhomboidal, while in polar view the cysts are circular to reniform in outline. Strong polar compression is observed in most specimens. The smaller forms are usually more rhomboidal in ambitus and circular in polar view. The epitract and hypotract are of a similar size; their flanks are straight to convex. No antapical horns are present; however, a small apical projection can usually be recognized. The phragma is ornamented with straight or curved, distally pointed spines; these may be solid and are usually circular at their bases. The number of spines present on each cyst is extremely variable; however, the smaller the forms are the longer and less abundant the spines appear to be. One row of spines delineates the apical region of the test. The cingular zone is wide, circular, and outlined by more strongly developed spines. The sulcus is usually observed in polar view and it helps to give the sometimes characteristic reniform shape to the cyst. It is fairly narrow and moderately deep. The archeopyle reflects 2a (intercalary) plate; it is relatively small, laterally elongate, and six sided. The wall is thin, often colourless, single layered , and with a smooth to psilate ornamentation.
Remarks (annotated): A continuous morphologic gradation between the large, reniform-shaped to the smaller circular forms seems apparent. Generally, the longer the spines and the less abundant they are, the smaller the cysts tend to be.
Thecal affinity: The larger cyst forms have been shown by incubation experiments (Wall and Dale, 1968) to give rise to Peridinium conicum. The smaller cyst forms produce (Wall and Dale, 1968) thecal characteristics of Peridinium nudum.
Supplemental description: Reid, 1977, p.448
The cysts have polar compression giving a rhomboidal shape in equatorial view. The wall is thin, single layered, with a smooth surface which is ornamented by rows of solid curved spines. Two rows form a V shaped outline at the base of the ventral sulcus which expands in a posterior direction from the girdle. Processes are not present in the sulcus itself and in the anterior ventral areas. The girdle is circular. Two small scars in the ventral sulcus reflect the position of the flagellar pores. A laterally elongated six-sided archeopyle is found with rounded angles. The colour of specimens varies from colourless, to grey brown, to dark brown.