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Eisenackia reticulata
Eisenackia reticulata (Damassa, 1979b, p.196,198,200, pl.3, figs.1-6; pl.4, figs.4-5; text-fig.3) Quattrocchio and Sarjeant, 2003, p.146.
Originally Alisocysta, subsequently (and now) Eisenackia.
Holotype: Damassa, 1979b, pl.4, figs.4-5; text-fig.3.
Age: Early Paleocene.
(Damassa, 1979b):
Diagnosis: Cyst subspherical to ovoidal; paratabulation indicated by low penitabular ridges. Intratabular ornamentation resembling a low reticulum; reticulation may intend into the parsutural areas. Archepyle Type (tA), operculum simple, free.
Derivation of name: Latin, reticulatus, netlike with reference to the intratabular ornamentation.
Description: Cyst subspherical to ovoidal, averaging 55 µm in length, 51 µm in width. Paratabulation indicated by thin penitabular ridges 2-3 µm in height. Intratabular regions are ornamented with reticulate features of low relief (about 1-2µm in height). Reticulation may also be developed to a lesser degree in the parasutural areas. End of paracingulum offset by a distance slightly less than the width of the paracingulum. Archeopyle Type (tA), operculum simple, free, about 24x29 µm. Parasulcal notch conspicuously developed. Anterior sulcal paraplate slender and subtriangular in outline. Paraplate 6’’ reduced with respect to others in the precingular series. Cingular paraplates indicated by elongate, subrectangular penitabular ridges. Postcingular paraplates completely developed althoughparaplate 1’’’is small and inconspicuous. Five sulcal paraplates indicated. Antapical paraplate pentagonal in shape, bordered by 1p, 3’’’, 4’’’, 5’’’, ps.
Paratabulation: 4’, 6’’, 6c, 5s, 1p, 6’’’, 1’’’’.
Remarks: Alisocysta reticulate is very similar to Eisenackia crassitabuklata Deflandre & Cookson, 1955. The two species apparently differ only with respect ot the degree of development of the intratabular reticulations (R. Helby, pers. comm.). In A. reticulate the reticulate features are low, generally less than half the height of the penitabular ridges, whereas in E. crassitabulata the reticulate structure fills the entire space delineated by the penitabular ridges. Thus in E. crassitabulata the paratabulation is indiacted by distinctly positive features (“elevated, platform-like features”, Stover and Evitt, 1978, p. 16). A. reticulate can be described in terms of a morphological variation in which penitabular paratabulation is combined with intratabular ornamentation. It is clear from inspection of illustrated specimens as well as those used in this study that the genera Allisocysta and Eisenackia are identical in paratabulation pattern and type of archeopyle. The configuration of the paraplates on the hypocyst of E. crassitabulata was clearly illustrated by Deflande and Cookson (1955, Text-Figures 8, 11, 12, 15) and exactly corresponds to that of A. circumtabulata, as well as that of A. rugolirata and A. reticulate.
Material and occurrence: PL 4764, 10 specimens and an isolated operculum.
Originally Alisocysta, subsequently (and now) Eisenackia.
Holotype: Damassa, 1979b, pl.4, figs.4-5; text-fig.3.
Age: Early Paleocene.
(Damassa, 1979b):
Diagnosis: Cyst subspherical to ovoidal; paratabulation indicated by low penitabular ridges. Intratabular ornamentation resembling a low reticulum; reticulation may intend into the parsutural areas. Archepyle Type (tA), operculum simple, free.
Derivation of name: Latin, reticulatus, netlike with reference to the intratabular ornamentation.
Description: Cyst subspherical to ovoidal, averaging 55 µm in length, 51 µm in width. Paratabulation indicated by thin penitabular ridges 2-3 µm in height. Intratabular regions are ornamented with reticulate features of low relief (about 1-2µm in height). Reticulation may also be developed to a lesser degree in the parasutural areas. End of paracingulum offset by a distance slightly less than the width of the paracingulum. Archeopyle Type (tA), operculum simple, free, about 24x29 µm. Parasulcal notch conspicuously developed. Anterior sulcal paraplate slender and subtriangular in outline. Paraplate 6’’ reduced with respect to others in the precingular series. Cingular paraplates indicated by elongate, subrectangular penitabular ridges. Postcingular paraplates completely developed althoughparaplate 1’’’is small and inconspicuous. Five sulcal paraplates indicated. Antapical paraplate pentagonal in shape, bordered by 1p, 3’’’, 4’’’, 5’’’, ps.
Paratabulation: 4’, 6’’, 6c, 5s, 1p, 6’’’, 1’’’’.
Remarks: Alisocysta reticulate is very similar to Eisenackia crassitabuklata Deflandre & Cookson, 1955. The two species apparently differ only with respect ot the degree of development of the intratabular reticulations (R. Helby, pers. comm.). In A. reticulate the reticulate features are low, generally less than half the height of the penitabular ridges, whereas in E. crassitabulata the reticulate structure fills the entire space delineated by the penitabular ridges. Thus in E. crassitabulata the paratabulation is indiacted by distinctly positive features (“elevated, platform-like features”, Stover and Evitt, 1978, p. 16). A. reticulate can be described in terms of a morphological variation in which penitabular paratabulation is combined with intratabular ornamentation. It is clear from inspection of illustrated specimens as well as those used in this study that the genera Allisocysta and Eisenackia are identical in paratabulation pattern and type of archeopyle. The configuration of the paraplates on the hypocyst of E. crassitabulata was clearly illustrated by Deflande and Cookson (1955, Text-Figures 8, 11, 12, 15) and exactly corresponds to that of A. circumtabulata, as well as that of A. rugolirata and A. reticulate.
Material and occurrence: PL 4764, 10 specimens and an isolated operculum.