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Palaeocystodinium reductum
Palaeocystodinium reductum May, 1980; Emendation: Kirsch, 1991, p.120, as Biconidinium reductum.
Now Biconidinium. Originally Palaeocystodinium, subsequently (and now) Biconidinium
Taxonomic junior synonym: Svalbardella parva (name not validly published), according to Slimani (2001a, p.192).
Holotype: May, 1980, pl.21, fig.20
Locus typicus: Atlantic Highlands, New Jersey
Stratum typicum: Campanian-Maastrichtian
Original description: May, 1980, p.84-85
Periblast spindle-shaped with extended apical and antapical horns; slightly compressed dorso-ventrally, and ovoidal in polar view; periphragm smooth. Horns not as long as endoblast; are pointed to digitate. Antapical horn bears slight deflection similar in position to the accessory spike of P. australinum. Endoblast ovoidal, separated from periblast by continuous lateral and polar pericoels; occupies central bulge of spindle; endophragm smooth. Nontabulated. Cingulum formed of low folds in periphragm; especially noticeable in optical cross section; slightly levorotatory less than 1 cingulum width offset. Sulcus barely traceable, formed of slight periphragm depression extending antapically from between terminal ends of cingulum. Archeopyle not observed.
Dimensions:
Holotype L x W, 113 x 42 µm; endoblast L x W, 43 x 36 µm; apical horn 27 µm; antapical horn 27 µm; lateral pericoels ca. 4 µm on each side in optical section. Observed range (4 specimens measured from top of endoblast 27-29 µm; antapical horn measured from bottom of endoblast 24-29 µm; endoblast L x W, 42-43 µm x 35-36 µm. Endophragm less than 1 µm; periphragm less than 1 µm.
Discussion: The characteristic features of P. reductum are the reduced size and abbreviated horns as compared to P. golzowense Alberti 1961 and P. australinum (C 1965). The presence of cingulum and sulcus, and the absence of an archeopyle are also distinctive. The assignment of this species into Palaeocystodinium is tentative, until further forms are observed which may display the archeopyle type.
Affinities:
May, 1980, p.84-85: P. reductum is similar in appearancc to P. ? denticulatum Alberti 1961; however, it lacks the ribbing or striae on the horns, and bears a consistent pericoel about the entire margin of the endoblast. P. australinum and P. golzowense both have much extended horns, giving greater length; whereas P. reductum has relatively abbreviated horns. The apparent lack of an archeopyle (at least the difficulty in detecting it), the size, and the presence of cingulum and sulcus would generally separate D. reductum from P. golzowense and P. australinum.
Now Biconidinium. Originally Palaeocystodinium, subsequently (and now) Biconidinium
Taxonomic junior synonym: Svalbardella parva (name not validly published), according to Slimani (2001a, p.192).
Holotype: May, 1980, pl.21, fig.20
Locus typicus: Atlantic Highlands, New Jersey
Stratum typicum: Campanian-Maastrichtian
Original description: May, 1980, p.84-85
Periblast spindle-shaped with extended apical and antapical horns; slightly compressed dorso-ventrally, and ovoidal in polar view; periphragm smooth. Horns not as long as endoblast; are pointed to digitate. Antapical horn bears slight deflection similar in position to the accessory spike of P. australinum. Endoblast ovoidal, separated from periblast by continuous lateral and polar pericoels; occupies central bulge of spindle; endophragm smooth. Nontabulated. Cingulum formed of low folds in periphragm; especially noticeable in optical cross section; slightly levorotatory less than 1 cingulum width offset. Sulcus barely traceable, formed of slight periphragm depression extending antapically from between terminal ends of cingulum. Archeopyle not observed.
Dimensions:
Holotype L x W, 113 x 42 µm; endoblast L x W, 43 x 36 µm; apical horn 27 µm; antapical horn 27 µm; lateral pericoels ca. 4 µm on each side in optical section. Observed range (4 specimens measured from top of endoblast 27-29 µm; antapical horn measured from bottom of endoblast 24-29 µm; endoblast L x W, 42-43 µm x 35-36 µm. Endophragm less than 1 µm; periphragm less than 1 µm.
Discussion: The characteristic features of P. reductum are the reduced size and abbreviated horns as compared to P. golzowense Alberti 1961 and P. australinum (C 1965). The presence of cingulum and sulcus, and the absence of an archeopyle are also distinctive. The assignment of this species into Palaeocystodinium is tentative, until further forms are observed which may display the archeopyle type.
Affinities:
May, 1980, p.84-85: P. reductum is similar in appearancc to P. ? denticulatum Alberti 1961; however, it lacks the ribbing or striae on the horns, and bears a consistent pericoel about the entire margin of the endoblast. P. australinum and P. golzowense both have much extended horns, giving greater length; whereas P. reductum has relatively abbreviated horns. The apparent lack of an archeopyle (at least the difficulty in detecting it), the size, and the presence of cingulum and sulcus would generally separate D. reductum from P. golzowense and P. australinum.