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Achomosphaera operculata
From Fensome et al., 2019:
Achomosphaera? operculata, Sah et al., 1970, p.144, pl.1, figs.1–2.
Holotype: Sah et al., 1970, pl.1, fig.1.
NOW Operculodinium.
Originally Achomosphaera, subsequently Achomosphaera?, thirdly (and now) Operculodinium.
Questionable assignment: Stover and Evitt (1978, p.139).
Age: Late Cretaceous.
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Original description: [Sah et al., 1970, p. 144]:
Achomosphaera operculata sp. nov.
PI. 1, Figs. 1-2
Holotype- PI. 1, Fig. 1. Size 42 x 41 μ.
Slide no. 3638.
No. of specimens studied- 16.
Diagnosis - Cysts circular, 30-45 x 28-44 μ. Archeopyle precingular, simple, processes well developed, branched at tips; cyst membrane thin, sculptured with grana or coni.
Description - Cysts sometimes subcircular or oval due to irregular foldings. Archeopyle well defined in most specimens, ± rhomboidal. Processes 20-30 μ long, tapered, with or without branched tips. Cyst membrane 1-1·5 μ thick, surface granulose or sometimes conied or both these elements may be interspersed together; elements up to 1 μ in height, generally closely placed and uniformly distributed.
Comparison - Achomosphaera sagena Dav. & Will. (1966) compares with the present species in the presence of similar sculptural element but the former is readily distinguishable by its thick cyst membrane. A. neptuni (Eisen.) Gocht (1959) also resembles A. operculata in shape, size and nature of the archeopyle, but differs in having well developed branched processes and reticulate or fibrous cyst membrane. A. ramulifera var. perforata Dav. & Will. (1966) has an oval shape and perforate processes.
Achomosphaera? operculata, Sah et al., 1970, p.144, pl.1, figs.1–2.
Holotype: Sah et al., 1970, pl.1, fig.1.
NOW Operculodinium.
Originally Achomosphaera, subsequently Achomosphaera?, thirdly (and now) Operculodinium.
Questionable assignment: Stover and Evitt (1978, p.139).
Age: Late Cretaceous.
---------------------------------------------------------------------------------------------------
Original description: [Sah et al., 1970, p. 144]:
Achomosphaera operculata sp. nov.
PI. 1, Figs. 1-2
Holotype- PI. 1, Fig. 1. Size 42 x 41 μ.
Slide no. 3638.
No. of specimens studied- 16.
Diagnosis - Cysts circular, 30-45 x 28-44 μ. Archeopyle precingular, simple, processes well developed, branched at tips; cyst membrane thin, sculptured with grana or coni.
Description - Cysts sometimes subcircular or oval due to irregular foldings. Archeopyle well defined in most specimens, ± rhomboidal. Processes 20-30 μ long, tapered, with or without branched tips. Cyst membrane 1-1·5 μ thick, surface granulose or sometimes conied or both these elements may be interspersed together; elements up to 1 μ in height, generally closely placed and uniformly distributed.
Comparison - Achomosphaera sagena Dav. & Will. (1966) compares with the present species in the presence of similar sculptural element but the former is readily distinguishable by its thick cyst membrane. A. neptuni (Eisen.) Gocht (1959) also resembles A. operculata in shape, size and nature of the archeopyle, but differs in having well developed branched processes and reticulate or fibrous cyst membrane. A. ramulifera var. perforata Dav. & Will. (1966) has an oval shape and perforate processes.