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Achomosphaera expansa
From Fensome et al., 2019:
Achomosphaera expansa, Stover and Hardenbol, 1994, p.33–34, pl.5, figs.30a–b,31a–c; pl.6, figs.32a–b.
Holotype: Stover and Hardenbol, 1994, pl.5, figs.30a–b.
Age: Rupelian.
Paratypes: Stover and Hardenbol, 1994, plate 5, figures 31a-c, and figures 32a-b
Locus typicus: Belgium
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Original description as Achomosphaera expansa: [Stover and Hardenbol, 1994, p. 33-34]:
Description:
Cysts skolochorate with subspherical to ellipsoidal bodies.
Endophragm and periphragm smooth and appressed except at the bases of processes; endophragm thicker than periphragm. Processes, which are formed by the periphragm, short relative to body length. Width of processes differs considerably although their length is fairly constant on individual specimens. Processes expanded proximally and most are not joined by parasutural septa. However, closely adjacent processes, particularly those in the paracingular area, may have amalgamated bases or be connected by low septa. Distally, the processes are expanded and branched repeatedly to form relatively simple to complex, irregularly margined, vasiform, fenestrate terminations.
Openings in fenestrations variable in size and shape. A few to many processes may be connected distally by narrow trabeculae.
The middorsal precingular archeopyle has a monoplacoid, secate operculum.
Paratabulation is evidently gonyaulacoid although the general absence of parasutural features makes the number, position and relationship of the paraplates difficult to discern and interpret.
Paracingular processes are typically more complex than others and two, relatively wide processes are present in the antapical polar area. Parasulcal processes absent.
Dimensions/Size:
intermediate; overall length 65 to 85 µm, body length 43 to 55 µm, body width 34 to 50 µm, process length 13.5 to 22 µm (most are between 15 and 20 µm, wall about 1 µm thick).
Comparison/Affinities:
Achomosphaera expansa is similar to A. andalousiensis Jan du Chene 1977 emended Jan du Chêne and Londeix 1988 by having processes with generally more complex fenestrate endings that lack spur-like projections and by having some processes connected by trabeculae. the new species differs from A. argesensis Demetrescue 1989 by having more complex distal terminations of the processes and by not having a flat antapical process. Achomosphaera andalousiensis and A. argesensis occur in post-Paleogene strata.
Achomosphaera expansa, Stover and Hardenbol, 1994, p.33–34, pl.5, figs.30a–b,31a–c; pl.6, figs.32a–b.
Holotype: Stover and Hardenbol, 1994, pl.5, figs.30a–b.
Age: Rupelian.
Paratypes: Stover and Hardenbol, 1994, plate 5, figures 31a-c, and figures 32a-b
Locus typicus: Belgium
---------------------------------------------------------------------------------------------------
Original description as Achomosphaera expansa: [Stover and Hardenbol, 1994, p. 33-34]:
Description:
Cysts skolochorate with subspherical to ellipsoidal bodies.
Endophragm and periphragm smooth and appressed except at the bases of processes; endophragm thicker than periphragm. Processes, which are formed by the periphragm, short relative to body length. Width of processes differs considerably although their length is fairly constant on individual specimens. Processes expanded proximally and most are not joined by parasutural septa. However, closely adjacent processes, particularly those in the paracingular area, may have amalgamated bases or be connected by low septa. Distally, the processes are expanded and branched repeatedly to form relatively simple to complex, irregularly margined, vasiform, fenestrate terminations.
Openings in fenestrations variable in size and shape. A few to many processes may be connected distally by narrow trabeculae.
The middorsal precingular archeopyle has a monoplacoid, secate operculum.
Paratabulation is evidently gonyaulacoid although the general absence of parasutural features makes the number, position and relationship of the paraplates difficult to discern and interpret.
Paracingular processes are typically more complex than others and two, relatively wide processes are present in the antapical polar area. Parasulcal processes absent.
Dimensions/Size:
intermediate; overall length 65 to 85 µm, body length 43 to 55 µm, body width 34 to 50 µm, process length 13.5 to 22 µm (most are between 15 and 20 µm, wall about 1 µm thick).
Comparison/Affinities:
Achomosphaera expansa is similar to A. andalousiensis Jan du Chene 1977 emended Jan du Chêne and Londeix 1988 by having processes with generally more complex fenestrate endings that lack spur-like projections and by having some processes connected by trabeculae. the new species differs from A. argesensis Demetrescue 1989 by having more complex distal terminations of the processes and by not having a flat antapical process. Achomosphaera andalousiensis and A. argesensis occur in post-Paleogene strata.