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Sentusidinium asymmetricum
Sentusidinium asymmetricum (Pocock, 1972) Jansonius, 1986
Originally Leiosphaeridia (Appendix A), subsequently Sentusidinium, thirdly (and now) Pilosidinium.
Taxonomic junior synonym: Sentusidinium (as Pilosidinium) fibrosum, according to Courtinat in Fauconnier and Masure, 2004, p.447.
Holotype: Pocock, 1972, pl.26, fig.29;Jansonius, 1986, pl.3, figs.9-10
Locus typicus: Royalite DeWinton, Western Canada
Stratum typicum: Late Bajotian
Original descirption: Pocock, 1972, p.107: Leiosphaeridia asymmetrica
Vesicle spherical, extended at one end in the form of a conical process about 5.0 µm long and with a basal width of 5.0 µm; densely spinose; spines pinnate; less than 0.5 µm wide and 2.5--3.0 µm long; spines spaced about 1.0 µm apart over most of the vesicle but less closely packed over an area about 5.0 µm wide situated immediately below the process frequent tears around the vesicle at the base of the process together with its complete absence from many specimens, suggests apical archeopyle formation; vesicle very thin; single-layered; colourless to pale yellow; size range 35.2 (36.6) 40.0 x 27.0 (31.0) 33.0 µm.
Supplemental description: Jansonius, 1986, p.219-220
(Holotype) 32 x 35 µm (exclusive of spinules); outline nearly circular, but at the apex drawn out so as to form a blunt conical prominence. Wall thin (ca 0.3 µm), hyaline, in places with a yellow hue; surface all-over densely covered by slender spinules, 2-3 µm tall, about 0.5 µm at their base, tapering, acuminate or buccinate, spaced at 1-2 µm, often bent or curved. Apical prominence nearly separated from body by angular tears that appear to reflect a paratabulation and indicate the presence of an apical archeopyle. No cingulum, no other evidence of paratabulation discernible.
Affinities:
Pocock, 1972, p.107: Pyriform shape and dense covering of spines characterize L. asymmetrica. The possible presence of an archeopyle suggests possible dinoflagellate affinity.
Jansonius, 1986, p.220: In other specimens the conical apical protrusion may be less discernible, and its appearance in the holotype in part is due to folding of the operculum; the archeopyle is delineated in most specimens, and the operculum lost in many. S. neophytensum (Ioannides et al.) Sarjeant & Stover is very similar, but differs in having a distinctly bigger spine at the apex. The large taper-folds in both specimens indicate an original shape close to spherical.
Originally Leiosphaeridia (Appendix A), subsequently Sentusidinium, thirdly (and now) Pilosidinium.
Taxonomic junior synonym: Sentusidinium (as Pilosidinium) fibrosum, according to Courtinat in Fauconnier and Masure, 2004, p.447.
Holotype: Pocock, 1972, pl.26, fig.29;Jansonius, 1986, pl.3, figs.9-10
Locus typicus: Royalite DeWinton, Western Canada
Stratum typicum: Late Bajotian
Original descirption: Pocock, 1972, p.107: Leiosphaeridia asymmetrica
Vesicle spherical, extended at one end in the form of a conical process about 5.0 µm long and with a basal width of 5.0 µm; densely spinose; spines pinnate; less than 0.5 µm wide and 2.5--3.0 µm long; spines spaced about 1.0 µm apart over most of the vesicle but less closely packed over an area about 5.0 µm wide situated immediately below the process frequent tears around the vesicle at the base of the process together with its complete absence from many specimens, suggests apical archeopyle formation; vesicle very thin; single-layered; colourless to pale yellow; size range 35.2 (36.6) 40.0 x 27.0 (31.0) 33.0 µm.
Supplemental description: Jansonius, 1986, p.219-220
(Holotype) 32 x 35 µm (exclusive of spinules); outline nearly circular, but at the apex drawn out so as to form a blunt conical prominence. Wall thin (ca 0.3 µm), hyaline, in places with a yellow hue; surface all-over densely covered by slender spinules, 2-3 µm tall, about 0.5 µm at their base, tapering, acuminate or buccinate, spaced at 1-2 µm, often bent or curved. Apical prominence nearly separated from body by angular tears that appear to reflect a paratabulation and indicate the presence of an apical archeopyle. No cingulum, no other evidence of paratabulation discernible.
Affinities:
Pocock, 1972, p.107: Pyriform shape and dense covering of spines characterize L. asymmetrica. The possible presence of an archeopyle suggests possible dinoflagellate affinity.
Jansonius, 1986, p.220: In other specimens the conical apical protrusion may be less discernible, and its appearance in the holotype in part is due to folding of the operculum; the archeopyle is delineated in most specimens, and the operculum lost in many. S. neophytensum (Ioannides et al.) Sarjeant & Stover is very similar, but differs in having a distinctly bigger spine at the apex. The large taper-folds in both specimens indicate an original shape close to spherical.