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Cassiculosphaeridia parvula
Cassiculosphaeridia parvula, Batten and Lister, 1988
Holotype: Batyten and Lister, 1988, figs.2c,d
Locus typicus: Cowleaze Chine Member of the Vectis Formation, Isle of Wight, Great Britain.
Stratum typicum: Barremian
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Original description: [Batten and Lister, 1988, p. 343]:
Diagnosis:
Small spherical to subspherical proximate cyst; maximum diameter 29(34)44 x 29(35)45 µm (20 specimens). Phragma thin (c.1 µm), probably two-layered, of very finely granulate structure, bearing an outer layer typically consisting of a reticulum more or less clearly delineated by low, sinuous, membraneous muri (c.2 µm high and 1 µm wide) supported by short rod-like structures. Lumina subpolygonal to irregular in shape, usually complete, varying in size (2-7 µm in diameter).
Rarely paracingulum weakly suggested by alignment of lumina. Parasulcal area occasionally indicated by absence of lumina or by incomplete or reduced muri.
Paratabulation otherwise sometimes expressed by short accessory archeopyle sutures, denoting presence of ?six precingular paraplates and a parasulcal notch.
Archeopyle formed by detachment of apical series but may also involve small intercalary paraplates. Operculum simple, angular in outline, usually remains attached after dehiscence.
Affinities and Remarks:
The preservation of this species in Wealden assemblages varies considerably. Some specimens exhibit a well-defined reticulum of relatively sturdy muri; others are very flimsy and degraded, sometimes to the extent that this sculpture is barely recognizable. Many of those recovered from the Weald Clay Group exhibit a reticulation that is largely confined to the parasutural boundaries. The archeopyle is usually developed but the operculum is almost always attached. In the rare specimens in which it is missing the archeopyle suture is complete without evidence of tearing, whereas in the majority the operculum appears to be adnate with only partial development of the suture. The angularity of the margin of the operculum suggests that it may be similar to that of Microdinium Cookson and Eisenack, 1960 emend. Stover and Evitt, 1978 with a series of small intercalaries surrounding the apical series.
Holotype: Batyten and Lister, 1988, figs.2c,d
Locus typicus: Cowleaze Chine Member of the Vectis Formation, Isle of Wight, Great Britain.
Stratum typicum: Barremian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Batten and Lister, 1988, p. 343]:
Diagnosis:
Small spherical to subspherical proximate cyst; maximum diameter 29(34)44 x 29(35)45 µm (20 specimens). Phragma thin (c.1 µm), probably two-layered, of very finely granulate structure, bearing an outer layer typically consisting of a reticulum more or less clearly delineated by low, sinuous, membraneous muri (c.2 µm high and 1 µm wide) supported by short rod-like structures. Lumina subpolygonal to irregular in shape, usually complete, varying in size (2-7 µm in diameter).
Rarely paracingulum weakly suggested by alignment of lumina. Parasulcal area occasionally indicated by absence of lumina or by incomplete or reduced muri.
Paratabulation otherwise sometimes expressed by short accessory archeopyle sutures, denoting presence of ?six precingular paraplates and a parasulcal notch.
Archeopyle formed by detachment of apical series but may also involve small intercalary paraplates. Operculum simple, angular in outline, usually remains attached after dehiscence.
Affinities and Remarks:
The preservation of this species in Wealden assemblages varies considerably. Some specimens exhibit a well-defined reticulum of relatively sturdy muri; others are very flimsy and degraded, sometimes to the extent that this sculpture is barely recognizable. Many of those recovered from the Weald Clay Group exhibit a reticulation that is largely confined to the parasutural boundaries. The archeopyle is usually developed but the operculum is almost always attached. In the rare specimens in which it is missing the archeopyle suture is complete without evidence of tearing, whereas in the majority the operculum appears to be adnate with only partial development of the suture. The angularity of the margin of the operculum suggests that it may be similar to that of Microdinium Cookson and Eisenack, 1960 emend. Stover and Evitt, 1978 with a series of small intercalaries surrounding the apical series.