Back
Leptodinium membranigerum
Leptodinium membranigerum Gerlach, 1961; emend. Sarjeant, 1984
Originally (and now) Leptodinium, subsequently Impagidinium?.
Holotype: Gerlach, 1961, pl.26, figs.1-3 (lost according to Sarjeant, 1984)
Lectotype: Gerlach, 1961, pl.26, fig.7, text-fig.5; Sarjeant, 1984, pl.1, fig.1,3, text-figs.1A-B; Jan du Chêne et al., 1986, pl.67, figs.17-18 (designated by Sarjeant, 1984)
Locus typicus: Emsboren boring no. 7, NW Germany
Stratum typicum: Late Oligocene
Translation Gerlach, 1961: Sarjeant, 1984
Original diagnosis: Gerlach, 1961, p. 162-163
A species of the genus Leptodinium with oval theca. Tabulation formula as given in the generic diagnosis; 4', 6", 5''', 1p and 1''''. Epitheca larger and more elongate than the rounded hypotheca. Girdle furrow spiral, formed of six plates. Offset of its ends somewhat more than a furrow breadth. Longitudinal furrow wholly undifferentiated. Sutures of plates marked by low hyaline crests, shell membrane appearing to bear a thornlike point at the position of convergence of two crests. Plates finely granulate, membrane relatively thin.
Description:
The majority of specimens of this species are excellently preserved, allowing all details of the tabulation to be observed. The monomorphic shell is composed of distinctly convex plates. The individual sutures of the plates are covered with low, slightly wavy, hyaline ridges. Occasionally, a slight serration of the edge can be seen. At the junction of two edges, the membrane is projected into a pointed, thorn-like protrusion. These corner protrusions become particularly long at the apex. The tabulation of the elongated epithet consists of four apical plates and six precingulate plates. The elongated 1' lies ventrally in the direct continuation of the longitudinal furrow. Next to it on the ventral side is the 4', also elongated and about 1.5 times as large as the 1'. The second and third apical plates, of considerably more compact outline, continue the apex region on the dorsal side. The precingulates are relatively large, with the exception of the 1" and 6" plates, which are somewhat reduced. The ventral 1" and 6" plates are trapezoidal in outline, and they are partially bordered by curved sides, while the dorsal precingulates have a trapezoidal shape. The 2", 3", and 4" plates lie in the dorsal circumflex of the epitheca. A pyloma is sometimes found in place of the 3" plate. The girdle groove is spiral and about 5 microns wide. It divides the theca into two unequal sections, of which the epitheca is elongated and considerably larger than the more compact, semicircular hypotheca. The six plates that make up the girdle groove are bordered by hyaline seams, similar to the usual plates. The offset of the ends of the cingulum is slightly more than one width of the cingulum.
The longitudinal furrow shows no differentiation. It extends from the first apical plate to the antapical plate, is bordered by curved sides in the upper narrow part, and widens at the height of the upper displaced end of the transverse furrow.
The hypothalamus consists of five postequatorial plates, one accessory plate, and a polygonal antapical plate, which is slightly displaced ventrally. The dorsally located 2''', 3''', and 4''' are elongated trapeze-shaped and larger than the ventral 1''' and 5'''. All plates are finely punctured. The membrane of the sheaths is relatively coarse and light yellow to yellowish-brown in color.
Dimensions:
holotype: 55:47
paratypes: 59:44, 63:53
Maximum: 70:62
minimum: 55:47
Average: 62:51 (10 measurements)
Emended diagnosis: Sarjeant, 1984, p. 75-76
Cyst proximate, holotabulate, and acavate; relatively thin but composed of two closely appressed wall layers. Ambitus broadly ovoidal, with epitract markedly larger than hypotract. Low crests, undulate to irregularly scalloped or echinate distally, define the paratabulation 4', 6", 6c, 6''', 2p, 1'''', ?6s. Paraplate 4" is quite large and asymmetrically pentagonal, having a fairly long boundary with a quadrate 6"; this boundary intersects that of 1" in a position anterior to that of 1" with the sulcus. All precingular paraplates are larger than their postcingular equivalents. The right boundary of the small, elongate paraplate 1''' is poorly marked; for this reason the sulcus, which broadens posteriorly, may appear to have the form of an inverted, broad-hafted axe with its blade to the right. Faint lines divide the sulcus into one anterior, at least four median and one (or two?) posterior paraplates. Two posterior intercalary paraplates of similar size separate the sulcus from the rather small antapical paraplate. The cingulum is of moderate breadth, forming a feeble laevorotatory spiral such that its two ends differ in anteroposterior position only by the cingulum's breadth. Surface of phragma uniformly granulate.
Archaeopyle single-plate precingular (type P) formed by the opening or loss of paraplate 3'''.
Dimensions: Holotype (in lateral view): length 55 µm, breadth 47 µm. Lectotype (in slightly oblique dorsoventral view and slightly flattened): length 74 µm, breadth 66 µm . Paratype (in lateral view): length 63 µm, breadth 53 µm. Range of dimensions: length 55-74 µm), breadth 47-63 µm (near 51 µm). Material: 10 specimens.
Originally (and now) Leptodinium, subsequently Impagidinium?.
Holotype: Gerlach, 1961, pl.26, figs.1-3 (lost according to Sarjeant, 1984)
Lectotype: Gerlach, 1961, pl.26, fig.7, text-fig.5; Sarjeant, 1984, pl.1, fig.1,3, text-figs.1A-B; Jan du Chêne et al., 1986, pl.67, figs.17-18 (designated by Sarjeant, 1984)
Locus typicus: Emsboren boring no. 7, NW Germany
Stratum typicum: Late Oligocene
Translation Gerlach, 1961: Sarjeant, 1984
Original diagnosis: Gerlach, 1961, p. 162-163
A species of the genus Leptodinium with oval theca. Tabulation formula as given in the generic diagnosis; 4', 6", 5''', 1p and 1''''. Epitheca larger and more elongate than the rounded hypotheca. Girdle furrow spiral, formed of six plates. Offset of its ends somewhat more than a furrow breadth. Longitudinal furrow wholly undifferentiated. Sutures of plates marked by low hyaline crests, shell membrane appearing to bear a thornlike point at the position of convergence of two crests. Plates finely granulate, membrane relatively thin.
Description:
The majority of specimens of this species are excellently preserved, allowing all details of the tabulation to be observed. The monomorphic shell is composed of distinctly convex plates. The individual sutures of the plates are covered with low, slightly wavy, hyaline ridges. Occasionally, a slight serration of the edge can be seen. At the junction of two edges, the membrane is projected into a pointed, thorn-like protrusion. These corner protrusions become particularly long at the apex. The tabulation of the elongated epithet consists of four apical plates and six precingulate plates. The elongated 1' lies ventrally in the direct continuation of the longitudinal furrow. Next to it on the ventral side is the 4', also elongated and about 1.5 times as large as the 1'. The second and third apical plates, of considerably more compact outline, continue the apex region on the dorsal side. The precingulates are relatively large, with the exception of the 1" and 6" plates, which are somewhat reduced. The ventral 1" and 6" plates are trapezoidal in outline, and they are partially bordered by curved sides, while the dorsal precingulates have a trapezoidal shape. The 2", 3", and 4" plates lie in the dorsal circumflex of the epitheca. A pyloma is sometimes found in place of the 3" plate. The girdle groove is spiral and about 5 microns wide. It divides the theca into two unequal sections, of which the epitheca is elongated and considerably larger than the more compact, semicircular hypotheca. The six plates that make up the girdle groove are bordered by hyaline seams, similar to the usual plates. The offset of the ends of the cingulum is slightly more than one width of the cingulum.
The longitudinal furrow shows no differentiation. It extends from the first apical plate to the antapical plate, is bordered by curved sides in the upper narrow part, and widens at the height of the upper displaced end of the transverse furrow.
The hypothalamus consists of five postequatorial plates, one accessory plate, and a polygonal antapical plate, which is slightly displaced ventrally. The dorsally located 2''', 3''', and 4''' are elongated trapeze-shaped and larger than the ventral 1''' and 5'''. All plates are finely punctured. The membrane of the sheaths is relatively coarse and light yellow to yellowish-brown in color.
Dimensions:
holotype: 55:47
paratypes: 59:44, 63:53
Maximum: 70:62
minimum: 55:47
Average: 62:51 (10 measurements)
Emended diagnosis: Sarjeant, 1984, p. 75-76
Cyst proximate, holotabulate, and acavate; relatively thin but composed of two closely appressed wall layers. Ambitus broadly ovoidal, with epitract markedly larger than hypotract. Low crests, undulate to irregularly scalloped or echinate distally, define the paratabulation 4', 6", 6c, 6''', 2p, 1'''', ?6s. Paraplate 4" is quite large and asymmetrically pentagonal, having a fairly long boundary with a quadrate 6"; this boundary intersects that of 1" in a position anterior to that of 1" with the sulcus. All precingular paraplates are larger than their postcingular equivalents. The right boundary of the small, elongate paraplate 1''' is poorly marked; for this reason the sulcus, which broadens posteriorly, may appear to have the form of an inverted, broad-hafted axe with its blade to the right. Faint lines divide the sulcus into one anterior, at least four median and one (or two?) posterior paraplates. Two posterior intercalary paraplates of similar size separate the sulcus from the rather small antapical paraplate. The cingulum is of moderate breadth, forming a feeble laevorotatory spiral such that its two ends differ in anteroposterior position only by the cingulum's breadth. Surface of phragma uniformly granulate.
Archaeopyle single-plate precingular (type P) formed by the opening or loss of paraplate 3'''.
Dimensions: Holotype (in lateral view): length 55 µm, breadth 47 µm. Lectotype (in slightly oblique dorsoventral view and slightly flattened): length 74 µm, breadth 66 µm . Paratype (in lateral view): length 63 µm, breadth 53 µm. Range of dimensions: length 55-74 µm), breadth 47-63 µm (near 51 µm). Material: 10 specimens.