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Chiropteridium conispinum
Chiropteridium conispinum, Williams, 1978
Holotype: Williams, 1978, pl.2, figs.1-2
Age: Oligocene
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Original description: [Williams, 1978]:
Diagnosis:
Chorate cyst with subcircular ambitus. Phragma microreticulate, lumina very irregular in size and shape. On the ventral surface linear membranes originating on the first and fifth precingular paraplates, respectively, run towards the antapex.
Membranous processes, generally restricted to the dorsal surface, are proximally conical or subconical and distally may branch into slender tubules. The processes are nontabular.
Archeopyle apical, tetratabular.
Parasulcal notch visible.
Paratabulation indeterminate other than 1 pra, 4', 6".
Description:
The ventral surface of the cyst always bears two membranes with their entire margins running apically antapically. These originate on the apical paraplates in one specimen. In specimens lacking an operculum, they always originate towards the midline on paraplates 1" and 5", respectively, and extend to the antapex, where they form two distinct antapical projections. These membranes may have a single process along their length, at which point there is a change in direction, and antapically. Occasionally a third membrane runs laterally across the dorsal surface in the vicinity of the postcingular antapical paraplate boundaries. The processes, generally restricted to the operculum and the dorsal surface are membranous, proximally conical to subconical and sometimes open on one side, in effect forming a soleate structure. In some specimens they are ribbed. The processes rarely exceed 12 in number and apparently do not relate to paratabulation. In the vicinity of the archeopyle margin they appear to be located on the parasutures between adjacent precingular paraplates. Distally the processes may be acuminate closed, or produced into slender tubules up to 12 µm in length. One operculum possesses five such processes, united to each other by membranes. Four of these processes are peripherally located on paraplates 1' through 4'. The fifth is centrally located and is presumably a preapical. Of the precingulars, 6" is always devoid of processes. The other precingulars, excluding 1" and 5", appear to bear processes suturally. Some specimens show lateral process alignment in what is presumably the vicinity of the paracingulum.
Dimensions:
Cyst width, 64-81 µm, length (less operculum) 59-70 µm. Processes up to 20 µm, linear membrane rarely exceeding 10 µm in height. Number of specimens measured, 6.
Holotype: Diameter width 87 µm, length 64 µm. Processes up to 20 µm.
Remarks:
Only one species of Chiropteridium, C. aspinatum (Gerlach) Brosius, bears a superficial resemblance to C. conispinum. C. aspinatum does not, however, possess processes and the apically-antapically aligned membranes when examined under the scanning electron microscope are seen to form closed structures with one wall on the lateral dorsal surface, and one on the lateral ventral surface.
Holotype: Williams, 1978, pl.2, figs.1-2
Age: Oligocene
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Original description: [Williams, 1978]:
Diagnosis:
Chorate cyst with subcircular ambitus. Phragma microreticulate, lumina very irregular in size and shape. On the ventral surface linear membranes originating on the first and fifth precingular paraplates, respectively, run towards the antapex.
Membranous processes, generally restricted to the dorsal surface, are proximally conical or subconical and distally may branch into slender tubules. The processes are nontabular.
Archeopyle apical, tetratabular.
Parasulcal notch visible.
Paratabulation indeterminate other than 1 pra, 4', 6".
Description:
The ventral surface of the cyst always bears two membranes with their entire margins running apically antapically. These originate on the apical paraplates in one specimen. In specimens lacking an operculum, they always originate towards the midline on paraplates 1" and 5", respectively, and extend to the antapex, where they form two distinct antapical projections. These membranes may have a single process along their length, at which point there is a change in direction, and antapically. Occasionally a third membrane runs laterally across the dorsal surface in the vicinity of the postcingular antapical paraplate boundaries. The processes, generally restricted to the operculum and the dorsal surface are membranous, proximally conical to subconical and sometimes open on one side, in effect forming a soleate structure. In some specimens they are ribbed. The processes rarely exceed 12 in number and apparently do not relate to paratabulation. In the vicinity of the archeopyle margin they appear to be located on the parasutures between adjacent precingular paraplates. Distally the processes may be acuminate closed, or produced into slender tubules up to 12 µm in length. One operculum possesses five such processes, united to each other by membranes. Four of these processes are peripherally located on paraplates 1' through 4'. The fifth is centrally located and is presumably a preapical. Of the precingulars, 6" is always devoid of processes. The other precingulars, excluding 1" and 5", appear to bear processes suturally. Some specimens show lateral process alignment in what is presumably the vicinity of the paracingulum.
Dimensions:
Cyst width, 64-81 µm, length (less operculum) 59-70 µm. Processes up to 20 µm, linear membrane rarely exceeding 10 µm in height. Number of specimens measured, 6.
Holotype: Diameter width 87 µm, length 64 µm. Processes up to 20 µm.
Remarks:
Only one species of Chiropteridium, C. aspinatum (Gerlach) Brosius, bears a superficial resemblance to C. conispinum. C. aspinatum does not, however, possess processes and the apically-antapically aligned membranes when examined under the scanning electron microscope are seen to form closed structures with one wall on the lateral dorsal surface, and one on the lateral ventral surface.