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Nidarocysta
From Williams et al., 2017:
[Nidarocysta, Monteil, 1997, p. 390, 392-394.
Type species: Nidarocysta jubilaea, Monteil, 1997 (pl.3, fig.3; pl.4, figs.1-6; text-figs.6a-b)]
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Original description: [Monteil, 1997]:
Description:
Cysts proximate, acavate, biconical with a pointed apex; autophragm fragile, thin and transparent, psilate to minutely ornamented; paratabulation gonyaulacaean, indicated by a parasutural thread-like pattern, formula: 2pr, 0-1a, 4’,6”, 6c, 6’”, 1p, 1””, 3-?5s; precingular archeopyle, type (P)rsa, with an unusual opening mode; archeopyle not developed or only expressed by random splitting (rs); adnate operculum (3”).
Diagnosis:
Shape: Biconical with a pointed apex and a rounded antapex.
Wall relationships: Parasutural thread-like pattern, typically separated from the cyst wall; surface ornamentation psilate to scabrate, or minutely granulate.
Archeopyle: Precingular archeopyle, type (P)rsa, with an unusual opening mode; archeopyle not developed or only expressed by partial random splitting (rs) around 3" margin and sometimes adjacent paraplates; adnate operculum (3").
Paratabulation: clearly indicated by parasutural thread-like structures; gonyaulacacean, formula: 2pr, 0-1a, 4', 6", 6c, 6"', 1p, 1"", 3-?5s.
Paracingulum: indicated by six rectangular transversely gate paraplates; laevorotatory. Parasulcus: clearly indicated and subdivided, rs and ls boundary excepted.
Size:
Small to intermediate; about 45 μm to 55 μm in diameter and 50 μm to 65 μm in length.
Remarks:
The sexiform gonyaulacacean paratabulation pattern with L-type ventral organisation and neutral torsion, exhibited by Nidarocysta gen. nov., dictates its inclusion in the Subfamily Leptodinioideae (Fensome et al., 1993). Subfamily Cribroperidinioideae possesses the same ventral organisation, but differs in showing a dextral torsion. And S-type ventral organisation characterises the subfamiliy Gonyaulacoideae. Comparison Nidarocysta gen. nov. differs from Leptodinium Klement 1960 emend. Stover & Evitt 1978 in having an adnate operculum (3"), a very unusual archeopyle opening mode (random splitting) and in lacking "true" parasutural septa.
[Nidarocysta, Monteil, 1997, p. 390, 392-394.
Type species: Nidarocysta jubilaea, Monteil, 1997 (pl.3, fig.3; pl.4, figs.1-6; text-figs.6a-b)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Monteil, 1997]:
Description:
Cysts proximate, acavate, biconical with a pointed apex; autophragm fragile, thin and transparent, psilate to minutely ornamented; paratabulation gonyaulacaean, indicated by a parasutural thread-like pattern, formula: 2pr, 0-1a, 4’,6”, 6c, 6’”, 1p, 1””, 3-?5s; precingular archeopyle, type (P)rsa, with an unusual opening mode; archeopyle not developed or only expressed by random splitting (rs); adnate operculum (3”).
Diagnosis:
Shape: Biconical with a pointed apex and a rounded antapex.
Wall relationships: Parasutural thread-like pattern, typically separated from the cyst wall; surface ornamentation psilate to scabrate, or minutely granulate.
Archeopyle: Precingular archeopyle, type (P)rsa, with an unusual opening mode; archeopyle not developed or only expressed by partial random splitting (rs) around 3" margin and sometimes adjacent paraplates; adnate operculum (3").
Paratabulation: clearly indicated by parasutural thread-like structures; gonyaulacacean, formula: 2pr, 0-1a, 4', 6", 6c, 6"', 1p, 1"", 3-?5s.
Paracingulum: indicated by six rectangular transversely gate paraplates; laevorotatory. Parasulcus: clearly indicated and subdivided, rs and ls boundary excepted.
Size:
Small to intermediate; about 45 μm to 55 μm in diameter and 50 μm to 65 μm in length.
Remarks:
The sexiform gonyaulacacean paratabulation pattern with L-type ventral organisation and neutral torsion, exhibited by Nidarocysta gen. nov., dictates its inclusion in the Subfamily Leptodinioideae (Fensome et al., 1993). Subfamily Cribroperidinioideae possesses the same ventral organisation, but differs in showing a dextral torsion. And S-type ventral organisation characterises the subfamiliy Gonyaulacoideae. Comparison Nidarocysta gen. nov. differs from Leptodinium Klement 1960 emend. Stover & Evitt 1978 in having an adnate operculum (3"), a very unusual archeopyle opening mode (random splitting) and in lacking "true" parasutural septa.