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Sentusidinium sparsibarbatum
Sentusidinium sparsibarbatum Erkmen and Sarjeant, 1980
Taxonomic junior synonym: Sentusidinium hexagonale, according to Courtinat in Fauconnier and Masure (2004, p.486).
Holotype: Erkmen and Sarjeant, 1980, pl.6, fig.9; text-fig.4a
Paratype: Erkmen and Sarjeant, 1980
Locus typicus: Tidmoor Point, Chickerell, near Weymouth, Dorset, England
Stratum typicum: Late Callovian
Original diagnosis: Erkmen and Sarjeant, 1980, p. 55
Cyst ovoidal to elongate-ovoidal. Processes in moderate number (less that 150 on a complete cyst); they are positioned with apparent irregularity, but are probably generally gonal or sutural in situation, though some appear to correspond in position to the centres of paraplates. Process length variable on each individual cyst but always short (between one-sixteenth and one-ninth of the shortest cyst diameter in length ) and slender, tapering slightly above the base and flaring slightly again towards the tip. Process tips rarely acuminate, commonly blunt, capitate or symmetrically or asymmetrically bifurcate, the two branches being in exceptional instances themselves capitate or briefly bifurcate. Surface of periphragm smooth to minutely granular or punctate, but without coarser ornament. Archaeopyle apical, with a distinct sulcal notch and with up to seven or eight accessory archaeopyle sutures, usually extending quite deeply into the epitract.
Dimensions: holotype: length (apex lacking) 28 µm, breadth 34 µm, length of processes c. 2 µm. Paratype: length (apex lacking) 37 µm, breadth 32 µm, length of processes c, 3,5 µm.
Range of dimensions: length (apices lacking ) 25-47 µm (mean 32 µm ), breadth 18,5-42 µm (mean 27,2 µm), length of processes 1-5 µm (mean 2 µm).
Affinities:
Erkmen and Sarjeant, 1980, p. 56: This species differs from all others currently placed in the genus Sentusidinium in its comparatively low number of processes. their apparently essentially gonal or sutural position. and the unusually large nurnber of accessory archaeopyle sutures. Despite careful examination of all specimens availab]e to us we could not conclusively determine the exact number of these sutures: but we feel a paratabulation to be suggested more in accord with that of Rhaetogonyaulax than with the simpler gonyaulacoid pattern. Thus despite the general similarity of these forms with other members of the genus Sentusidinium we believe they may well be a product of a different evolutionary lineage and may ultimately deserve generic separation.
Taxonomic junior synonym: Sentusidinium hexagonale, according to Courtinat in Fauconnier and Masure (2004, p.486).
Holotype: Erkmen and Sarjeant, 1980, pl.6, fig.9; text-fig.4a
Paratype: Erkmen and Sarjeant, 1980
Locus typicus: Tidmoor Point, Chickerell, near Weymouth, Dorset, England
Stratum typicum: Late Callovian
Original diagnosis: Erkmen and Sarjeant, 1980, p. 55
Cyst ovoidal to elongate-ovoidal. Processes in moderate number (less that 150 on a complete cyst); they are positioned with apparent irregularity, but are probably generally gonal or sutural in situation, though some appear to correspond in position to the centres of paraplates. Process length variable on each individual cyst but always short (between one-sixteenth and one-ninth of the shortest cyst diameter in length ) and slender, tapering slightly above the base and flaring slightly again towards the tip. Process tips rarely acuminate, commonly blunt, capitate or symmetrically or asymmetrically bifurcate, the two branches being in exceptional instances themselves capitate or briefly bifurcate. Surface of periphragm smooth to minutely granular or punctate, but without coarser ornament. Archaeopyle apical, with a distinct sulcal notch and with up to seven or eight accessory archaeopyle sutures, usually extending quite deeply into the epitract.
Dimensions: holotype: length (apex lacking) 28 µm, breadth 34 µm, length of processes c. 2 µm. Paratype: length (apex lacking) 37 µm, breadth 32 µm, length of processes c, 3,5 µm.
Range of dimensions: length (apices lacking ) 25-47 µm (mean 32 µm ), breadth 18,5-42 µm (mean 27,2 µm), length of processes 1-5 µm (mean 2 µm).
Affinities:
Erkmen and Sarjeant, 1980, p. 56: This species differs from all others currently placed in the genus Sentusidinium in its comparatively low number of processes. their apparently essentially gonal or sutural position. and the unusually large nurnber of accessory archaeopyle sutures. Despite careful examination of all specimens availab]e to us we could not conclusively determine the exact number of these sutures: but we feel a paratabulation to be suggested more in accord with that of Rhaetogonyaulax than with the simpler gonyaulacoid pattern. Thus despite the general similarity of these forms with other members of the genus Sentusidinium we believe they may well be a product of a different evolutionary lineage and may ultimately deserve generic separation.