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Achomosphaera
From Williams et al., 2017:
[Achomosphaera, Evitt, 1963, p. 163
Tax. sr. syn.: Spiniferites according to Duxbury (1983, p.54-55) - however, Lentin and Williams (1989, p.3) retained Achomosphaera; Taxonomic junior synonym: Hystrichostrogylon by implication in Eaton (1976, p.237), who included the "type species", Hystrichostrogylon membraniphorum, in Achomosphaera - however, Stover and Evitt (1978, p.165) retained Hystrichostrogylon
Type species: as Hystrichosphaeridium ramuliferum, Deflandre, 1937b (pl.14 (al. pl.11), fig.5)]
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Original description: [Evitt, 1963]:
Diagnosis: Test consists of a spherical to ellipsoidal central body with precingular archaeopyle and furcate, spine-like processes like those in Hystrichosphaera in both structure and distribution, but without sutural ridges or septa connecting their bases in that genus. Tips of processes not interconnected. Wall two-layered; layers typically in close contact between bases of processes.
Affinities:
Diagnostic characters are the precingular archaeopyle and Hystrichosphaera-like processes, combined with an absence of sutural ridges or septa between process bases and an absence of trabeculae between process tips. Some of the equatorial processes reflecting the girdle are often large and double as in Hystrichosphaera. Processes at the poles may also be larger than ones between polar areas and equator. Hystrichosphaera, the most closely similar genus, and Nematosphaeropsis are distinguished by well-developed sutural ridges or septa, and Nematosphaeropsis has trabecular connections between process tips. Despite the lack of sutural ridges in Achomosphaera, the positional relationship of its processes to other features (e.g. poles, equator, archaeopyle) shows that the processes are sutural.
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Modified description:
Stover and Evitt 1978, p. 138-139:
Synopsis: Cysts proximochorate to skolochorate; body subsperical, bearing isolated processes with only trifurcate tips or with trifurcate and bifurcate tips; processes without distal inter- connections, and proximal markings between process bases absent or limited to faint parasutural lines; paratabulation gonyaulacacean, typically obscurely discernible; archeopyle precingular, Type P.
Description:
Shape: Body subspherical.
Wall relationships: Autophragm only, or endophragm and periphragm appressed between processes.
Wall features: Parasutural features between process bases faint (e.g., traces of low ridges, rows of granules) or absent altogether; features may be present over entire cyst or only locally. Processes solid or hollow, gonal only, or gonal and intergonal; positions difficult to determine in absence of parasutural markings; process tips characteristically trifurcate (gonal) or bifurcate (intergonal), as on Spiniferites, and all primary furcations may be additionally bifurcate one or more times. Wall between processes smooth to variously ornamented with features of low relief; wall rarely thick and structured.
Paratabulation: Commonly obscure, decipherable only from positions of gonal processes if not indicated by faint parasutural features; gonyaulacacean, formula not normally determinable.
Archeopyle: Precingular, Type P (3`` only); operculum free.
Paracingulum: Indicated, if at all, by parasutural lines.
Parasulcus: Indicated, if at all, by parasutural lines.
Size: Small to large.
Affinities:
Achomosphaera differs from Spiniferites either in lacking parasutural features altogether or in having only faint linear markings between bases of processes. Transitional forms with parasutural features intermediate between those on typical species of each genus make consistent identification difficult.
[Achomosphaera, Evitt, 1963, p. 163
Tax. sr. syn.: Spiniferites according to Duxbury (1983, p.54-55) - however, Lentin and Williams (1989, p.3) retained Achomosphaera; Taxonomic junior synonym: Hystrichostrogylon by implication in Eaton (1976, p.237), who included the "type species", Hystrichostrogylon membraniphorum, in Achomosphaera - however, Stover and Evitt (1978, p.165) retained Hystrichostrogylon
Type species: as Hystrichosphaeridium ramuliferum, Deflandre, 1937b (pl.14 (al. pl.11), fig.5)]
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Original description: [Evitt, 1963]:
Diagnosis: Test consists of a spherical to ellipsoidal central body with precingular archaeopyle and furcate, spine-like processes like those in Hystrichosphaera in both structure and distribution, but without sutural ridges or septa connecting their bases in that genus. Tips of processes not interconnected. Wall two-layered; layers typically in close contact between bases of processes.
Affinities:
Diagnostic characters are the precingular archaeopyle and Hystrichosphaera-like processes, combined with an absence of sutural ridges or septa between process bases and an absence of trabeculae between process tips. Some of the equatorial processes reflecting the girdle are often large and double as in Hystrichosphaera. Processes at the poles may also be larger than ones between polar areas and equator. Hystrichosphaera, the most closely similar genus, and Nematosphaeropsis are distinguished by well-developed sutural ridges or septa, and Nematosphaeropsis has trabecular connections between process tips. Despite the lack of sutural ridges in Achomosphaera, the positional relationship of its processes to other features (e.g. poles, equator, archaeopyle) shows that the processes are sutural.
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Modified description:
Stover and Evitt 1978, p. 138-139:
Synopsis: Cysts proximochorate to skolochorate; body subsperical, bearing isolated processes with only trifurcate tips or with trifurcate and bifurcate tips; processes without distal inter- connections, and proximal markings between process bases absent or limited to faint parasutural lines; paratabulation gonyaulacacean, typically obscurely discernible; archeopyle precingular, Type P.
Description:
Shape: Body subspherical.
Wall relationships: Autophragm only, or endophragm and periphragm appressed between processes.
Wall features: Parasutural features between process bases faint (e.g., traces of low ridges, rows of granules) or absent altogether; features may be present over entire cyst or only locally. Processes solid or hollow, gonal only, or gonal and intergonal; positions difficult to determine in absence of parasutural markings; process tips characteristically trifurcate (gonal) or bifurcate (intergonal), as on Spiniferites, and all primary furcations may be additionally bifurcate one or more times. Wall between processes smooth to variously ornamented with features of low relief; wall rarely thick and structured.
Paratabulation: Commonly obscure, decipherable only from positions of gonal processes if not indicated by faint parasutural features; gonyaulacacean, formula not normally determinable.
Archeopyle: Precingular, Type P (3`` only); operculum free.
Paracingulum: Indicated, if at all, by parasutural lines.
Parasulcus: Indicated, if at all, by parasutural lines.
Size: Small to large.
Affinities:
Achomosphaera differs from Spiniferites either in lacking parasutural features altogether or in having only faint linear markings between bases of processes. Transitional forms with parasutural features intermediate between those on typical species of each genus make consistent identification difficult.