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Senoniasphaera ptomatis
Senoniasphaera ptomatis Helby, May and Partridge in Helby, 1987
Holotype: Helby, May and Partridge in Helby, 1987, fig.25A-D
Paratypes: Helby, May and Partridge in Helby, 1987
Locus typicus: Australia
Stratum typicum: Berriasian
Original description: Helby, May and Partridge in Helby, 1987, p.319-321
Proximate cyst, lenticular to compressed peridinioid; with low but distinct apical horn, 2 equatorial paracingular protrusions and 2 antapical horns. Left antapical horn larger and further from paracingulum, hypocyst markedly asymmetrical (Fig.25A-D). Cyst wall 2- layered, circumcavate; outlines of endophragm and periphragm essentially similar. Endophragm smooth, scabrate or granulate. Periphragm smooth, perforate or granulate in most regions, occasionally with low granular to rugoreticulate pandasutural ridges. Paratabulation expressed mainly by archeopyle, accessory archeopyle sutures and paracingulum. In some specimens cingular, postcingular and precingular paraplate boundaries marked by low pandasutural ridges (Fig.25E). Paratabulation intermittently expressed on posterior of cyst body and on apical and antapical horns. Interpretation of paraplates in the postcingular series varying between specimens as the small first postcingular plate is often poorly defined. Paratabulation formula 4", 6"", 6c, 6""", 1p, 1"""" (Fig.26). Archeopyle apical, type [tA], principal archeopyle suture zigzag with parasulcal notch offset to the left; operculum free. Paracingulum marked by distinctive protrusions of periphragm (Fig.251,R). Endophragm often with small, rounded protrusions at the paracingulum. Parasulcus marked by clear offsetting of paracingulum, smoother periphragm and possible parasutural folds at edge of parasulcus. Measurements. See Fig.24 for key to measurements. Fifty specimens from Lacepede-IA well, core-2 at 1072.9m in the D. Iobispinosum Zone were measured as:-- A, 65(77)90 µm; B, 56(67)80 µm; C, 57(76)100 µm; D, 50(66)80 µm; E, 91(99)110 µm; F, 70(75)83 µm.
Affinities:
Helby, May and Partridge in Helby, 1987, p.321: Senoniasphaera tabulata is larger, exhibits distinctive parasutural ridges and is not as obviously cavate as S. ptomatis. Specimens illustrated by Gitmez & Sarjeant (1972, pl. 14, figs 5 ,8) and loannides, Stavrinos & Downie (1977, pl.3, figs 12,13) as Hexagonifera jurassica Gitmez & Sarjeant 1972 were reassigned to Senoniasphaera by Lentin & Williams (1976). However, none of these specimens exhibit antapical or paracingular protrusions and the occurrence of an apical horn is questionable. I consider the reassignment of these forms to Senoniasphaera may be in error, although they do not conform to Hexagonifera Cookson & Eisenack emend. Stover & Evitt 1978. The shape of the periphragm on the specimen illustrated by Davey & Riley (in Thusu, 1978, pl.2, fig.8) and Davey (1979, pl.I, fig.3) as S. jurassica is similar to that of S. ptomatis but S. jurassica lacks distinct paracingular ridges on the periphragm and horn development on the endophragm.
Holotype: Helby, May and Partridge in Helby, 1987, fig.25A-D
Paratypes: Helby, May and Partridge in Helby, 1987
Locus typicus: Australia
Stratum typicum: Berriasian
Original description: Helby, May and Partridge in Helby, 1987, p.319-321
Proximate cyst, lenticular to compressed peridinioid; with low but distinct apical horn, 2 equatorial paracingular protrusions and 2 antapical horns. Left antapical horn larger and further from paracingulum, hypocyst markedly asymmetrical (Fig.25A-D). Cyst wall 2- layered, circumcavate; outlines of endophragm and periphragm essentially similar. Endophragm smooth, scabrate or granulate. Periphragm smooth, perforate or granulate in most regions, occasionally with low granular to rugoreticulate pandasutural ridges. Paratabulation expressed mainly by archeopyle, accessory archeopyle sutures and paracingulum. In some specimens cingular, postcingular and precingular paraplate boundaries marked by low pandasutural ridges (Fig.25E). Paratabulation intermittently expressed on posterior of cyst body and on apical and antapical horns. Interpretation of paraplates in the postcingular series varying between specimens as the small first postcingular plate is often poorly defined. Paratabulation formula 4", 6"", 6c, 6""", 1p, 1"""" (Fig.26). Archeopyle apical, type [tA], principal archeopyle suture zigzag with parasulcal notch offset to the left; operculum free. Paracingulum marked by distinctive protrusions of periphragm (Fig.251,R). Endophragm often with small, rounded protrusions at the paracingulum. Parasulcus marked by clear offsetting of paracingulum, smoother periphragm and possible parasutural folds at edge of parasulcus. Measurements. See Fig.24 for key to measurements. Fifty specimens from Lacepede-IA well, core-2 at 1072.9m in the D. Iobispinosum Zone were measured as:-- A, 65(77)90 µm; B, 56(67)80 µm; C, 57(76)100 µm; D, 50(66)80 µm; E, 91(99)110 µm; F, 70(75)83 µm.
Affinities:
Helby, May and Partridge in Helby, 1987, p.321: Senoniasphaera tabulata is larger, exhibits distinctive parasutural ridges and is not as obviously cavate as S. ptomatis. Specimens illustrated by Gitmez & Sarjeant (1972, pl. 14, figs 5 ,8) and loannides, Stavrinos & Downie (1977, pl.3, figs 12,13) as Hexagonifera jurassica Gitmez & Sarjeant 1972 were reassigned to Senoniasphaera by Lentin & Williams (1976). However, none of these specimens exhibit antapical or paracingular protrusions and the occurrence of an apical horn is questionable. I consider the reassignment of these forms to Senoniasphaera may be in error, although they do not conform to Hexagonifera Cookson & Eisenack emend. Stover & Evitt 1978. The shape of the periphragm on the specimen illustrated by Davey & Riley (in Thusu, 1978, pl.2, fig.8) and Davey (1979, pl.I, fig.3) as S. jurassica is similar to that of S. ptomatis but S. jurassica lacks distinct paracingular ridges on the periphragm and horn development on the endophragm.