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Cribroperidinium aceras
Cribroperidinium aceras (Eisenack, 1958) emend. Sarjeant, 1985
Originally Gonyaulax, subsequently Leptodinium, thirdly Acanthaulax?, fourthly (and now) Cribroperidinium; see also Gonyaulacysta? (combination not validly published).
Holotype: Eisenack, 1958, pl.21, fig.1; Sarjeant, 1985, pl.4, figs.1-2; Jan du Chêne et al., 1986, pl.2, figs.6-7
Paratype: Eisenack, 1958
Locus typicus: borehole at Marne, Feld Heide, north Germany
Stratum typicum: Aptian
Translation Eisenack, 1958: Sarjeant, 1985
Original diagnosis: Eisenack, 1958, p.391: Gonyaulax aceras
Shell oval, without horns. Epi- and hypotheca almost equal. Transverse furrow spiral, narrow, delimited by solid but low crests. Plate boundaries only partially marked by crests, these and the plate surfaces being set with short, pointed tubercles, so that the tabulation is scarcely discernible.
Emended description: Gitmez and Sarjeant, 1972, p.215: Leptodinium aceras
Cyst broadly ovoidal to subsphaerical, without appandages, with tabulation 4", 1a, 6"", 6c, 6""", 1p, 1pv and 1"""". Cingulum helicoid, laevorotatory; sulcus narrow, extending on both epitract and hypotract. Sutures in the form of low membraneous crests. Surface coarsly granular. Archaeopyle rarely developed, formed by the loss of plate 3"".
Emended diagnosis: Sarjeant, 1985, p.57, 59
Proximate, acavate, holotabulate cysts of moderately large size, ovoidal, with epitract and hypotract of closely comparable size and shape. Horns are lacking, though a slight prominence may be simulated by crests traversing the apex. Boundaries of cingulum marked by continuous, very low crests of undulose to irregularly echinate form; similar crests, continuous or discontinuous, or lines of tubercles mark the boundaries of the sulcus and paraplates. Accessory crests, similarly marked, are developed on most paraplates, singly or in concentric sets; and tubercles or short spines occur rarely in other positions within paraplates.
The paratabulation is thus determined only with difficulty, as follows:
?0pr, 4", 6", 6c, 6""", 1p, 1pv, 1"""". Paraplate 4" is elongate, of a blunted wedgeshape; the crest dividing it from 6" is quite short and joins that bordering 1" in a position markedly anterior to the junction of the latter paraplate with the sulcus. Paraplate 6" is larger in size than 4" and of asymmetrically pentagonal shape. Paraplates 1""" and 2""" are reduced to accommodate an especially large 1p. Paraplate 1pv is also unusually large, whereas 1"""" is relatively small. The sulcus is short and broad, occupying only the central portion of the ventral surface; however, its boundary with 1" and 1pv is marked only feebly (typically by lines of tubercles) so that, in some specimens, the sulcus may appear to extend almost from apex to antapex. The cingulum is of moderate breadth and degree of spirality, its two ends differing in anteroposterior position by only slightly more than its breadth. Archaeopyle not developed in specimens seen.
Originally Gonyaulax, subsequently Leptodinium, thirdly Acanthaulax?, fourthly (and now) Cribroperidinium; see also Gonyaulacysta? (combination not validly published).
Holotype: Eisenack, 1958, pl.21, fig.1; Sarjeant, 1985, pl.4, figs.1-2; Jan du Chêne et al., 1986, pl.2, figs.6-7
Paratype: Eisenack, 1958
Locus typicus: borehole at Marne, Feld Heide, north Germany
Stratum typicum: Aptian
Translation Eisenack, 1958: Sarjeant, 1985
Original diagnosis: Eisenack, 1958, p.391: Gonyaulax aceras
Shell oval, without horns. Epi- and hypotheca almost equal. Transverse furrow spiral, narrow, delimited by solid but low crests. Plate boundaries only partially marked by crests, these and the plate surfaces being set with short, pointed tubercles, so that the tabulation is scarcely discernible.
Emended description: Gitmez and Sarjeant, 1972, p.215: Leptodinium aceras
Cyst broadly ovoidal to subsphaerical, without appandages, with tabulation 4", 1a, 6"", 6c, 6""", 1p, 1pv and 1"""". Cingulum helicoid, laevorotatory; sulcus narrow, extending on both epitract and hypotract. Sutures in the form of low membraneous crests. Surface coarsly granular. Archaeopyle rarely developed, formed by the loss of plate 3"".
Emended diagnosis: Sarjeant, 1985, p.57, 59
Proximate, acavate, holotabulate cysts of moderately large size, ovoidal, with epitract and hypotract of closely comparable size and shape. Horns are lacking, though a slight prominence may be simulated by crests traversing the apex. Boundaries of cingulum marked by continuous, very low crests of undulose to irregularly echinate form; similar crests, continuous or discontinuous, or lines of tubercles mark the boundaries of the sulcus and paraplates. Accessory crests, similarly marked, are developed on most paraplates, singly or in concentric sets; and tubercles or short spines occur rarely in other positions within paraplates.
The paratabulation is thus determined only with difficulty, as follows:
?0pr, 4", 6", 6c, 6""", 1p, 1pv, 1"""". Paraplate 4" is elongate, of a blunted wedgeshape; the crest dividing it from 6" is quite short and joins that bordering 1" in a position markedly anterior to the junction of the latter paraplate with the sulcus. Paraplate 6" is larger in size than 4" and of asymmetrically pentagonal shape. Paraplates 1""" and 2""" are reduced to accommodate an especially large 1p. Paraplate 1pv is also unusually large, whereas 1"""" is relatively small. The sulcus is short and broad, occupying only the central portion of the ventral surface; however, its boundary with 1" and 1pv is marked only feebly (typically by lines of tubercles) so that, in some specimens, the sulcus may appear to extend almost from apex to antapex. The cingulum is of moderate breadth and degree of spirality, its two ends differing in anteroposterior position by only slightly more than its breadth. Archaeopyle not developed in specimens seen.