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Minisphaeridium
From Williams et al., 2017:
[Minisphaeridium, Fensome et al., 2009, p. 44
Type species: as Hystrichosphaeridium latirictum, Davey and Williams, 1966b (pl.10, fig.8)]
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Original description: [Fensome et al., 2009]:
Diagnosis:
Gonyaulacalean? cysts that are small (central body typically 20-25 μm across), proximochorate to generally chorate, with a spheroidal central body. Acavate. A tabulate; processes apparently mesotabular, tubular or taeniate, sometimes interconnected by membranes.
Archaeopyle apical, rarely apparent.
Remarks:
The above diagnosis can also serve as a synopsis.
This genus is characterised by its small size, the central body being on average about 20-25 μm in diameter. The first name to appear, in Morgenroth (1966), for forms here encompassed under Minisphaeridium was Cordosphaeridium inodes subsp. minimum. It was characterised by its small size and processes similar in shape to those of Cordosphaeridium cantharellus; the nature of the archaeopyle, however, was unclear. Slightly later, the name Hystrichosphaeridium latirictum, which has priority at specific rank, was published by Davey & Williams (1966b) for an essentially identical form: those authors reported an apical archaeopyle. Litosphaeridium? parvum of Matsuoka & Bujak (1988) also appears to be synonymous with Hystricho sphaeridium (now Minishaeridium) latirictum. Like Davey & Williams, Matsuoka & Bujak also reported an apical archaeopyle; this feature is usually hard to see in the present material, but has been well illustrated by de Verteuil & Norris (1996:caption to pl. 3, figs 1-5). No existing genus satisfactorily accommodates these diminutive chorate cysts with an apical archaeopyle. Hence, we propose the name Minisphaeridium. Labyrinthodinium is similar in its relatively small size and apical archaeopyle, but has a network of sinuous crests rather than discrete cylindrical processes.
[Minisphaeridium, Fensome et al., 2009, p. 44
Type species: as Hystrichosphaeridium latirictum, Davey and Williams, 1966b (pl.10, fig.8)]
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Original description: [Fensome et al., 2009]:
Diagnosis:
Gonyaulacalean? cysts that are small (central body typically 20-25 μm across), proximochorate to generally chorate, with a spheroidal central body. Acavate. A tabulate; processes apparently mesotabular, tubular or taeniate, sometimes interconnected by membranes.
Archaeopyle apical, rarely apparent.
Remarks:
The above diagnosis can also serve as a synopsis.
This genus is characterised by its small size, the central body being on average about 20-25 μm in diameter. The first name to appear, in Morgenroth (1966), for forms here encompassed under Minisphaeridium was Cordosphaeridium inodes subsp. minimum. It was characterised by its small size and processes similar in shape to those of Cordosphaeridium cantharellus; the nature of the archaeopyle, however, was unclear. Slightly later, the name Hystrichosphaeridium latirictum, which has priority at specific rank, was published by Davey & Williams (1966b) for an essentially identical form: those authors reported an apical archaeopyle. Litosphaeridium? parvum of Matsuoka & Bujak (1988) also appears to be synonymous with Hystricho sphaeridium (now Minishaeridium) latirictum. Like Davey & Williams, Matsuoka & Bujak also reported an apical archaeopyle; this feature is usually hard to see in the present material, but has been well illustrated by de Verteuil & Norris (1996:caption to pl. 3, figs 1-5). No existing genus satisfactorily accommodates these diminutive chorate cysts with an apical archaeopyle. Hence, we propose the name Minisphaeridium. Labyrinthodinium is similar in its relatively small size and apical archaeopyle, but has a network of sinuous crests rather than discrete cylindrical processes.