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Achomosphaera eggadania
Achomosphaera eggadania, Vieira, M. et al., 2018, p. 183
Holotype: Vieira, M. et al., 2018, Plate 1, figures 1–2
Type locality: southern part of the Ormen Lange field (Norway) over the Danian-aged reservoir
Local stratigraphical range: Danian (Early Paleocene)
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Original description: [Vieira, M. et al., 2018]:
Diagnosis:
Chorate to proximochorate cyst, spherical to subspherical in shape, composed of two layers, periphragm and endophragm adpressed between processes; the surface of the periphragm is very thin and psilate, the endophragm is thick up to 3 µm with evenly distributed, coarse grana up to 1.5 µm in diameter.
Precingular archaeopyle formed by displacement of the 3” paraplate, operculum is free. Processes are gonal, hollow to occasionally solid, usually trifurcate with bifurcation distally, the distal extremities bifid and not connected. The surface of the processes also exhibits less granulation (smooth to slightly granulate) than does the cyst body.
Dimensions:
Holotype: cyst body length 62.5 µm, width 67 µm (without processes); length 115 µm, width 115 µm (with processes), length of processes 29 µm
16 specimens measured: Diameter of cyst body 58 (65) 73 µm, cyst with processes 72.5 (109) 138 µm, length of processes 25 (32) 43 µm, width 5 (6) 10 µm
Affinities/Comparison:
The evenly distributed grana are characteristic of this species and therefore distinguish it from others. Achomosphaera alcicornu (Eisenack 1954) Davey & Williams 1966 closely resembles the new species but differs in its psilate to punctuate, rather than evenly granulate, cyst wall. Achomosphaera rassipellis (Deflandre & Cookson 1955) Stover & Evitt 1978 differs in having a very thick wall (up to 5 mm), and the processes
tend to be pale, thin and slightly fibrous. Hafniasphaera hyalospinosa Hansen (1977) and Hafniasphaera graciosa Hansen (1977) differ from the present species by the presence of a large and variable number of vesicles on both cyst body and processes, and generally a greater number of vesicles on the cyst wall. Thomsen & Heilmann-Clausen (1985) recorded Hafniasphaera graciosa from the Danian of Svejstrup.
Holotype: Vieira, M. et al., 2018, Plate 1, figures 1–2
Type locality: southern part of the Ormen Lange field (Norway) over the Danian-aged reservoir
Local stratigraphical range: Danian (Early Paleocene)
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Vieira, M. et al., 2018]:
Diagnosis:
Chorate to proximochorate cyst, spherical to subspherical in shape, composed of two layers, periphragm and endophragm adpressed between processes; the surface of the periphragm is very thin and psilate, the endophragm is thick up to 3 µm with evenly distributed, coarse grana up to 1.5 µm in diameter.
Precingular archaeopyle formed by displacement of the 3” paraplate, operculum is free. Processes are gonal, hollow to occasionally solid, usually trifurcate with bifurcation distally, the distal extremities bifid and not connected. The surface of the processes also exhibits less granulation (smooth to slightly granulate) than does the cyst body.
Dimensions:
Holotype: cyst body length 62.5 µm, width 67 µm (without processes); length 115 µm, width 115 µm (with processes), length of processes 29 µm
16 specimens measured: Diameter of cyst body 58 (65) 73 µm, cyst with processes 72.5 (109) 138 µm, length of processes 25 (32) 43 µm, width 5 (6) 10 µm
Affinities/Comparison:
The evenly distributed grana are characteristic of this species and therefore distinguish it from others. Achomosphaera alcicornu (Eisenack 1954) Davey & Williams 1966 closely resembles the new species but differs in its psilate to punctuate, rather than evenly granulate, cyst wall. Achomosphaera rassipellis (Deflandre & Cookson 1955) Stover & Evitt 1978 differs in having a very thick wall (up to 5 mm), and the processes
tend to be pale, thin and slightly fibrous. Hafniasphaera hyalospinosa Hansen (1977) and Hafniasphaera graciosa Hansen (1977) differ from the present species by the presence of a large and variable number of vesicles on both cyst body and processes, and generally a greater number of vesicles on the cyst wall. Thomsen & Heilmann-Clausen (1985) recorded Hafniasphaera graciosa from the Danian of Svejstrup.