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Membranosphaera granulata
Membranosphaera granulata Norvick in Norvick and Burger, 1976
Now Kallosphaeridium?. Originally Membranosphaera, subsequently (and now) Kallosphaeridium?.
Holotype: Norvick and Burger, 1976, pl.11, fig.9
Age: Cenomanian
Original description (Norvick and Burger, 1976):
Membranosphaera granulata sp. nov. (Pl.ll,fig.9;Pl.l2,fig.3)
Holotype: Plate 11, fig. 9. Bathurst Island No.2 well, core 4, 91.5 m, 298'6-11 M.F.P. 4437-1 :096:049 (CPC 12286). Width 31 µm, length without operculum 33 µm.
Derivation of name: From the Latin granulum, a small grain; with reference to the nature of the surface ornament.
Diagnosis: Cyst spherical or subspherical, proximate, acavate, and non-tabulate. Wall thin, with a variable and dense ornament of small grana, bacula, or clavae. Distal reticulum absent. Archaeopyle apical, with an entire or notched margin. Operculum attached by a sulcal tongue.
Description: Proximate, acavate and non-tabulate cysts, with a spherical or subspherical shape. The wall is thin (less than 0.5 µm) and ornamented by small grana, bacula, or clavae of variable shape and spacing. The grana may be as small as 0.5 µm in diameter and up to 1 µm apart. Where the ornament consists of bacula or clavae they reach 1 µm in length and are more closely spaced. The archaeopyle is apical, with an operculum attached by a sulcal neck. The margin of the archaeopyle is sometimes notched and the sulcal neck may be broad or narrow. Common specimens occur in which the sulcal neck is completely severed and the operculum is detached.
Dimensions: Width 27 µm (36 /Lm) 44 µm for 13 specimens.
Remarks: Batiacasphaera compta Drugg, 1970, from the upper Eocene of the American Gulf Coast, differs from M. granulata in having bacula which are arranged in a reticulate pattern, sometimes partly fused to form muri. B. baculata Drugg, 1970, also from the Gulf Coast upper Eocene, has randomly arranged bacula, but they are considerably larger than those of the Bathurst Island specimens. Neither of Drugg 's species was described as having attached opercula, and both are larger than M. granulata. M. maastrichtica Samoilovitch ofDrugg (1967) has bacula that occasionally bear a thin outer membrane. The clavate members of M. granulata approach this condition, but an outer membrane could not be positively identified in any of the available material. Some of the specimens resemble Forma M of Evitt (1967), from the Upper Cretaceous of California, which probably falls within the range of variation of M. granulata. Chytroeisphaeridia pocockii Sarjeant, 1968, from the Upper Jurassic of England, France, and Scotland, is granulate like M. granulata. However, it is somewhat larger and has never been figured with an attached operculum. In the Bathurst Island wells M granulata occurs fairly commonly throughout the succession.
Now Kallosphaeridium?. Originally Membranosphaera, subsequently (and now) Kallosphaeridium?.
Holotype: Norvick and Burger, 1976, pl.11, fig.9
Age: Cenomanian
Original description (Norvick and Burger, 1976):
Membranosphaera granulata sp. nov. (Pl.ll,fig.9;Pl.l2,fig.3)
Holotype: Plate 11, fig. 9. Bathurst Island No.2 well, core 4, 91.5 m, 298'6-11 M.F.P. 4437-1 :096:049 (CPC 12286). Width 31 µm, length without operculum 33 µm.
Derivation of name: From the Latin granulum, a small grain; with reference to the nature of the surface ornament.
Diagnosis: Cyst spherical or subspherical, proximate, acavate, and non-tabulate. Wall thin, with a variable and dense ornament of small grana, bacula, or clavae. Distal reticulum absent. Archaeopyle apical, with an entire or notched margin. Operculum attached by a sulcal tongue.
Description: Proximate, acavate and non-tabulate cysts, with a spherical or subspherical shape. The wall is thin (less than 0.5 µm) and ornamented by small grana, bacula, or clavae of variable shape and spacing. The grana may be as small as 0.5 µm in diameter and up to 1 µm apart. Where the ornament consists of bacula or clavae they reach 1 µm in length and are more closely spaced. The archaeopyle is apical, with an operculum attached by a sulcal neck. The margin of the archaeopyle is sometimes notched and the sulcal neck may be broad or narrow. Common specimens occur in which the sulcal neck is completely severed and the operculum is detached.
Dimensions: Width 27 µm (36 /Lm) 44 µm for 13 specimens.
Remarks: Batiacasphaera compta Drugg, 1970, from the upper Eocene of the American Gulf Coast, differs from M. granulata in having bacula which are arranged in a reticulate pattern, sometimes partly fused to form muri. B. baculata Drugg, 1970, also from the Gulf Coast upper Eocene, has randomly arranged bacula, but they are considerably larger than those of the Bathurst Island specimens. Neither of Drugg 's species was described as having attached opercula, and both are larger than M. granulata. M. maastrichtica Samoilovitch ofDrugg (1967) has bacula that occasionally bear a thin outer membrane. The clavate members of M. granulata approach this condition, but an outer membrane could not be positively identified in any of the available material. Some of the specimens resemble Forma M of Evitt (1967), from the Upper Cretaceous of California, which probably falls within the range of variation of M. granulata. Chytroeisphaeridia pocockii Sarjeant, 1968, from the Upper Jurassic of England, France, and Scotland, is granulate like M. granulata. However, it is somewhat larger and has never been figured with an attached operculum. In the Bathurst Island wells M granulata occurs fairly commonly throughout the succession.