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Rhynchodiniopsis microceras
Rhynchidiniopsis? microceras (Eisenack, 1958) emend. Sarjeant, 1985
Originally Gonyaulax, subsequently Gonyaulacysta, thirdly Rhynchodiniopsis, fourthly (and now) Rhynchodiniopsis?. Jan du Chêne et al., 1986 considered this to be a "provisionally accepted species" of Rhynchodiniopsis.
Holotype: Eisenack, 1958, pl.21, fig.13; Sarjeant, 1985, pl.6, figs.5-6, pl.7, fig.6, text-fig.4; Jan du Chêne et al., 1986, pl.99, figs.5-6 Locus typicus: between 761 and 767 m depth, borehole at Marne, Feld Heide, N Germany Stratum typicum: Late Aptian Translation Eisenack, 1958: Sarjeant, 1985
Original diagnosis: Eisenack, 1958, p.319: Gonyaulax microceras
Shell oval to polyhedral with short, solid, pointed apical horn. Epi- and hypotheca almost equal, with narrow, spiral transverse furrow enclosed by low crests. Plate boundaries formed by seams, not by crests. Plates granulate, or tuberculate with minute spines, which at times render prominent the plate boundaries.
Emended diagnosis: Sarjeant, 1985, p.67
Proximate, acavate, holotabulate cysts of moderate size, spheroidal to subpolygonal. Epitract and hypotract comparable in size and shape, the former giving rise to a short, tapering apical horn, rounded or blunt distally. Paraplate boundaries marked by very low, narrow crests, entire to echinate or acanthate; character of crests variable on a single specimen according to position. Surface of phragma shagreenate to rugulate. Paratabulation ?0pr, 1", 6-?7", 6c, 6""", 1p, 1pv, ?5s. Paraplate 4" is relatively small and almost quadrate, having a moderately long boundary with a large, elongate-polygonal 6". The boundary separating these paraplates intersects that bounding 1" in a position somewhat anterior to the junction of the latter paraplate with the sulcus. Paraplate 1" itself is unusually short and broad, its junction with the sulcus so poorly marked that the anterior sulcul paraplate appears to form part of 1" in some specimens. A row of four median sulcals occupy the centre of the ventral surface; the left-hand one, from its position, may be considered to form a part of the precingular series. Only one posterior sulcal appears developed. A large posterior ventral paraplate separates sulcus from antapex.
The cingulum is markedly laevorotatory, its two ends differing in anteroposterior position by twice its width. Paraplate 1""" is pentagonal and has no contact with a reduced posterior intercalary paraplate. Paraplate 2""" has an inbent left boundary to accommodate both these paraplates and is rather narrow. The antapical paraplate is quite large and almost hexagonal.
Archaeopyle single-plate precingular (type P), formed by loss of the large third precingular paraplate.
Dimensions: Holotype: overall length 64 µm, breadth 62 µm, length of apical horn c.7 µm. Range of dimensions: overall length 62-76 µm. Three specimens measured.
Originally Gonyaulax, subsequently Gonyaulacysta, thirdly Rhynchodiniopsis, fourthly (and now) Rhynchodiniopsis?. Jan du Chêne et al., 1986 considered this to be a "provisionally accepted species" of Rhynchodiniopsis.
Holotype: Eisenack, 1958, pl.21, fig.13; Sarjeant, 1985, pl.6, figs.5-6, pl.7, fig.6, text-fig.4; Jan du Chêne et al., 1986, pl.99, figs.5-6 Locus typicus: between 761 and 767 m depth, borehole at Marne, Feld Heide, N Germany Stratum typicum: Late Aptian Translation Eisenack, 1958: Sarjeant, 1985
Original diagnosis: Eisenack, 1958, p.319: Gonyaulax microceras
Shell oval to polyhedral with short, solid, pointed apical horn. Epi- and hypotheca almost equal, with narrow, spiral transverse furrow enclosed by low crests. Plate boundaries formed by seams, not by crests. Plates granulate, or tuberculate with minute spines, which at times render prominent the plate boundaries.
Emended diagnosis: Sarjeant, 1985, p.67
Proximate, acavate, holotabulate cysts of moderate size, spheroidal to subpolygonal. Epitract and hypotract comparable in size and shape, the former giving rise to a short, tapering apical horn, rounded or blunt distally. Paraplate boundaries marked by very low, narrow crests, entire to echinate or acanthate; character of crests variable on a single specimen according to position. Surface of phragma shagreenate to rugulate. Paratabulation ?0pr, 1", 6-?7", 6c, 6""", 1p, 1pv, ?5s. Paraplate 4" is relatively small and almost quadrate, having a moderately long boundary with a large, elongate-polygonal 6". The boundary separating these paraplates intersects that bounding 1" in a position somewhat anterior to the junction of the latter paraplate with the sulcus. Paraplate 1" itself is unusually short and broad, its junction with the sulcus so poorly marked that the anterior sulcul paraplate appears to form part of 1" in some specimens. A row of four median sulcals occupy the centre of the ventral surface; the left-hand one, from its position, may be considered to form a part of the precingular series. Only one posterior sulcal appears developed. A large posterior ventral paraplate separates sulcus from antapex.
The cingulum is markedly laevorotatory, its two ends differing in anteroposterior position by twice its width. Paraplate 1""" is pentagonal and has no contact with a reduced posterior intercalary paraplate. Paraplate 2""" has an inbent left boundary to accommodate both these paraplates and is rather narrow. The antapical paraplate is quite large and almost hexagonal.
Archaeopyle single-plate precingular (type P), formed by loss of the large third precingular paraplate.
Dimensions: Holotype: overall length 64 µm, breadth 62 µm, length of apical horn c.7 µm. Range of dimensions: overall length 62-76 µm. Three specimens measured.