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Chiropteridium aspinatum
Chiropteridium aspinatum, (Gerlach, 1961), Brosius, 1963
Now Membranophoridium. Originally (and now) Membranophoridium, subsequently Chriopteridium.
Holotype: Gerlach, 1961, pl.29, figs.7-8 (2 specimens)
Lectotype: Gerlach, 1961, pl.29, fig.7, designated by Gocht, 1969
Locus typicus: Emsbüren 7 bore, Germany
Stratum typicum: Middle Oligocene
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Original description as Membranophoridium aspinatum: [Gerlach, 1961, p. 199-200]: (Translation: Fensome et al., 1993):
Diagnosis:
Type species of the genus Membranophoridium with the following characteristics: theca surrounded on both sides by two parallel membranes which run meridionally. Upper and lower sides of the shell always lacking spines. Membrane granulate.
Description:
The outline of the theca is almost always semicircular. Based on abundant material (more than 300 specimens of this genus were prepared, all of which are open apically), it is evident that, although the apical cap is missing, the shells are not damaged accidentally. More likely, the polar cap is shed in consequence of the release of the protoplast, a pylome thus being formed. Moreover, this is unequivocally shown by the presence of some specimens of this genus, in an uncommon state of preservation, in which the polar cap is still loosely connected to the remaining part of the theca. This mode of pylome formation, as occurring predominantly in the genus Membranophoridium, is not uncommon in other hystrichosphaerids. It has been described for Tenua hystrix Eisenack, Hystrichosphaeridium tiara Klumpp, Hystrichosphaera [i.e. Histiophora] ornata Klement and for six species which Maier assigned to the genus Galea. The apical-antapical orientation of the shells results from the position of the escape hole. The dorsal-ventral orientation was guided by the weak depression on one side, which is arbitrarily defined as the ventral or lower surface. Characteristic of the new species M. aspinatum is the lack of isolated spines on the upper and lower sides of the theca. Laterally the shell is surrounded by two parallel, meridionally trending membranes, which are not interconnected antapically. On the lower side ..., broad, lobate, highly disrupted borders are set off from the two vertically running structures; their external margins are more or less smooth or marked by fine denticles. Ventrally, the theca is weakly indented between the structures. The two parts of the membrane separating the upper and lower sides are considerably smaller than the two ventrally situated membranes. At the antapex, they are prolonged into flaps, one of which distinctly surmounts the other.
The shell wall is granulate and of a yellow-brown colour.
Dimensions:
Size: Holotype: overall length 93 µm, overall width 110 µm, endocyst length 74 µm, endocyst width 84 µm.
Range of 20 specimens: overall length 74-110 µm, overall width 84-118 µm.
See Gerlach, 1961, p. 200 for further measurements.
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Description C. apinatum: "morphotype A":
Schindler, 1992, p. 201-202: (Transalation: GSC, courtesy R. Fensome):
Description:
Cyst two-layered. The roundish to oval endocyst is flattened dorsoventrally and antapically and fully enclosed in a delicate periphragm. Endophragm and periphragm, where they are in contact, are tightly appressed to each other. Starting at the line of their detachment, the periphragm forms hollow, distally closed fimbriae and processes (pericoel formation). The outline of these detachment boundaries is characteristic: They form a vertically oriented oval on the ventral side and a horizontal oval dorsally, so that these boundaries can also be used to orient the cyst.
Typical features of this morphotype are four lateral meridional, smooth-edged to distally weakly notched fimbriae (fig. 1), two antapical processes, and the horizontal, distally irregularly cleft fimbria (fig. 2) on the dorsal side in the vicinity of the antapex, which is at most proximally connected with the lateral fimbriae.
Since none of the specimens still has an operculum, no information can be given concerning the apical region or the length of the cysts.
The two antapical processes may have different In this case, the left process is distinctly longer lengths. than the right. If only one antapical process is present, it is on the left.
The apical archeopyle shows the 6-angled zigzag suture which is typical for Areoligeraceae. Little can be said regarding the paratabulation. Only, the distinctly leftward "parasulcal offset notch" (fig. 1b) on the ventral side indicates the apical end of the parasulcus as well as the lower boundary of the first apical plate.
In the area where endophragm and periphragm are attached, i.e., the mesal surface of the dorsal and ventral sides, and between the fimbriae and processes, the surface of the periphragm is distinctly granulate. The much smoother surface on fimbriae and processes is striking.
Also typical are the roundish to oval recesses (5-8 µm in diameter) in the periphragm, found at the base of the lateral, and the dorsal antapical fimbriae.
Measurements:
entire cyst: length: -breadth: 83-122 µm
endocyst: length: -breadth: 56-90 µm
Affinities:
("morphotype A"): This morphotype definitely corresponds to the original diagnosis of Chiropteridium aspinatum (Gerlach, 1961) Brosius, 1963. Only the range of variation with respect to size is greater in Morphotype A.
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Gocht, 1969, p.61-63: (Translation: Geological Survey of Canada)
Remarks/Description:
Gerlach chose Ch. aspinatum as the type species of her genus Membranophoridium (Gerlach, 1961). Since this species corresponds in all major characters with species of the genus Chiropteridium (type species Ch. lobospinosum Gocht, 1960, Membranophoridium should have been absorbed as a junior synonym. Gerlach erroneously illustrates two different specimens as holotype. Therefore the first (Gerlach, Plate 29 fig. 7) now becomes the holotype. The roundish, flattened central body is surrounded by a very fragile external membrane which is slightly appressed to it dorsally and ventrally or grown over it. The external membrane widens towards the sides and forms two projecting, parallel fimbriae on the left and two on the right, which circumscribe the body meridionally between the poles. As regular folds of the outer membrane, these fimbriae are hollow formations. The "ventral" pair of folds forms two antapical tips. Usually a fold runs inward from these tips and forms a horizontal ridge toward the dorsal side. The apical region was preserved only on two specimens. The folds converging toward the apex dissolve into several sinuations. On some of the specimens, "dorsal" and "ventral" are also marked by the detachment boundaries of the outer and inner membrane. On the (presumed) dorsal side, this boundary circumscribes an approximately oval field; on the ventral side, it is a longitudinally oriented area tapered toward the antapex. Also the roundish recesses of the outer membrane, which are especially characteristic of Chiropteridium, are directly adjacent to these lines; they are especially large on the dorsal side. The pylome is formed by the ejection of a 6-angled calotte; the torn edges of the opening show the typical notches. Only in exceptional cases are apical calottes still present in situ. Sometimes the outer membrane is supported on the inner body by individual processes.
Affinities:
The following characters link Ch. aspinatum with the other species Ch. lobospinosum Gocht, Ch. partispinatum (Gerlach), and Ch. dispersum Gocht: Two lateral pairs of fimbriate folds representing sinuations of the external membrane, heteropolarity, apical archeopyle, and roundish openings in the external membrane. In contrast to the species named, the distal edges of the fimbriae are smooth, and not divided into processes. Also the dorsal and the ventral side frequently differ. (A further aid to orientation, the weak indentation on the ventral side-- cf. Gerlach, 1961-- was not definitely observed on the Meckelfeld material.)
There is also considerable similarity to Cycloneph. membraniphorum Cookson and Eisenack, 1962, or at least the specimen illustrated by Cookson and Hughes, 1964. However, radial processes between the two membranes occur in Ch. aspinatum only in exceptional cases.
Now Membranophoridium. Originally (and now) Membranophoridium, subsequently Chriopteridium.
Holotype: Gerlach, 1961, pl.29, figs.7-8 (2 specimens)
Lectotype: Gerlach, 1961, pl.29, fig.7, designated by Gocht, 1969
Locus typicus: Emsbüren 7 bore, Germany
Stratum typicum: Middle Oligocene
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Original description as Membranophoridium aspinatum: [Gerlach, 1961, p. 199-200]: (Translation: Fensome et al., 1993):
Diagnosis:
Type species of the genus Membranophoridium with the following characteristics: theca surrounded on both sides by two parallel membranes which run meridionally. Upper and lower sides of the shell always lacking spines. Membrane granulate.
Description:
The outline of the theca is almost always semicircular. Based on abundant material (more than 300 specimens of this genus were prepared, all of which are open apically), it is evident that, although the apical cap is missing, the shells are not damaged accidentally. More likely, the polar cap is shed in consequence of the release of the protoplast, a pylome thus being formed. Moreover, this is unequivocally shown by the presence of some specimens of this genus, in an uncommon state of preservation, in which the polar cap is still loosely connected to the remaining part of the theca. This mode of pylome formation, as occurring predominantly in the genus Membranophoridium, is not uncommon in other hystrichosphaerids. It has been described for Tenua hystrix Eisenack, Hystrichosphaeridium tiara Klumpp, Hystrichosphaera [i.e. Histiophora] ornata Klement and for six species which Maier assigned to the genus Galea. The apical-antapical orientation of the shells results from the position of the escape hole. The dorsal-ventral orientation was guided by the weak depression on one side, which is arbitrarily defined as the ventral or lower surface. Characteristic of the new species M. aspinatum is the lack of isolated spines on the upper and lower sides of the theca. Laterally the shell is surrounded by two parallel, meridionally trending membranes, which are not interconnected antapically. On the lower side ..., broad, lobate, highly disrupted borders are set off from the two vertically running structures; their external margins are more or less smooth or marked by fine denticles. Ventrally, the theca is weakly indented between the structures. The two parts of the membrane separating the upper and lower sides are considerably smaller than the two ventrally situated membranes. At the antapex, they are prolonged into flaps, one of which distinctly surmounts the other.
The shell wall is granulate and of a yellow-brown colour.
Dimensions:
Size: Holotype: overall length 93 µm, overall width 110 µm, endocyst length 74 µm, endocyst width 84 µm.
Range of 20 specimens: overall length 74-110 µm, overall width 84-118 µm.
See Gerlach, 1961, p. 200 for further measurements.
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Description C. apinatum: "morphotype A":
Schindler, 1992, p. 201-202: (Transalation: GSC, courtesy R. Fensome):
Description:
Cyst two-layered. The roundish to oval endocyst is flattened dorsoventrally and antapically and fully enclosed in a delicate periphragm. Endophragm and periphragm, where they are in contact, are tightly appressed to each other. Starting at the line of their detachment, the periphragm forms hollow, distally closed fimbriae and processes (pericoel formation). The outline of these detachment boundaries is characteristic: They form a vertically oriented oval on the ventral side and a horizontal oval dorsally, so that these boundaries can also be used to orient the cyst.
Typical features of this morphotype are four lateral meridional, smooth-edged to distally weakly notched fimbriae (fig. 1), two antapical processes, and the horizontal, distally irregularly cleft fimbria (fig. 2) on the dorsal side in the vicinity of the antapex, which is at most proximally connected with the lateral fimbriae.
Since none of the specimens still has an operculum, no information can be given concerning the apical region or the length of the cysts.
The two antapical processes may have different In this case, the left process is distinctly longer lengths. than the right. If only one antapical process is present, it is on the left.
The apical archeopyle shows the 6-angled zigzag suture which is typical for Areoligeraceae. Little can be said regarding the paratabulation. Only, the distinctly leftward "parasulcal offset notch" (fig. 1b) on the ventral side indicates the apical end of the parasulcus as well as the lower boundary of the first apical plate.
In the area where endophragm and periphragm are attached, i.e., the mesal surface of the dorsal and ventral sides, and between the fimbriae and processes, the surface of the periphragm is distinctly granulate. The much smoother surface on fimbriae and processes is striking.
Also typical are the roundish to oval recesses (5-8 µm in diameter) in the periphragm, found at the base of the lateral, and the dorsal antapical fimbriae.
Measurements:
entire cyst: length: -breadth: 83-122 µm
endocyst: length: -breadth: 56-90 µm
Affinities:
("morphotype A"): This morphotype definitely corresponds to the original diagnosis of Chiropteridium aspinatum (Gerlach, 1961) Brosius, 1963. Only the range of variation with respect to size is greater in Morphotype A.
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Gocht, 1969, p.61-63: (Translation: Geological Survey of Canada)
Remarks/Description:
Gerlach chose Ch. aspinatum as the type species of her genus Membranophoridium (Gerlach, 1961). Since this species corresponds in all major characters with species of the genus Chiropteridium (type species Ch. lobospinosum Gocht, 1960, Membranophoridium should have been absorbed as a junior synonym. Gerlach erroneously illustrates two different specimens as holotype. Therefore the first (Gerlach, Plate 29 fig. 7) now becomes the holotype. The roundish, flattened central body is surrounded by a very fragile external membrane which is slightly appressed to it dorsally and ventrally or grown over it. The external membrane widens towards the sides and forms two projecting, parallel fimbriae on the left and two on the right, which circumscribe the body meridionally between the poles. As regular folds of the outer membrane, these fimbriae are hollow formations. The "ventral" pair of folds forms two antapical tips. Usually a fold runs inward from these tips and forms a horizontal ridge toward the dorsal side. The apical region was preserved only on two specimens. The folds converging toward the apex dissolve into several sinuations. On some of the specimens, "dorsal" and "ventral" are also marked by the detachment boundaries of the outer and inner membrane. On the (presumed) dorsal side, this boundary circumscribes an approximately oval field; on the ventral side, it is a longitudinally oriented area tapered toward the antapex. Also the roundish recesses of the outer membrane, which are especially characteristic of Chiropteridium, are directly adjacent to these lines; they are especially large on the dorsal side. The pylome is formed by the ejection of a 6-angled calotte; the torn edges of the opening show the typical notches. Only in exceptional cases are apical calottes still present in situ. Sometimes the outer membrane is supported on the inner body by individual processes.
Affinities:
The following characters link Ch. aspinatum with the other species Ch. lobospinosum Gocht, Ch. partispinatum (Gerlach), and Ch. dispersum Gocht: Two lateral pairs of fimbriate folds representing sinuations of the external membrane, heteropolarity, apical archeopyle, and roundish openings in the external membrane. In contrast to the species named, the distal edges of the fimbriae are smooth, and not divided into processes. Also the dorsal and the ventral side frequently differ. (A further aid to orientation, the weak indentation on the ventral side-- cf. Gerlach, 1961-- was not definitely observed on the Meckelfeld material.)
There is also considerable similarity to Cycloneph. membraniphorum Cookson and Eisenack, 1962, or at least the specimen illustrated by Cookson and Hughes, 1964. However, radial processes between the two membranes occur in Ch. aspinatum only in exceptional cases.